by Xenia Ragiadakou

[permalink] [raw]

Subject: Re: [PATCH V2] xen/virtio: Handle PCI devices which Host controller is described in DT

On 10/20/22 23:07, Oleksandr Tyshchenko wrote:
Hi Oleksandr
>
> On 20.10.22 21:11, Xenia Ragiadakou wrote:
>
> Hello Xenia
>
>
>> On 10/20/22 17:12, Oleksandr Tyshchenko wrote:
>>>
>>> On 20.10.22 11:24, Xenia Ragiadakou wrote:
>>>> On 10/19/22 22:41, Oleksandr Tyshchenko wrote:
>>>>
>>>> Hi Oleksandr
>>>
>>>
>>> Hello Xenia
>>>
>>>
>>>>
>>>>>
>>>>> On 19.10.22 11:47, Xenia Ragiadakou wrote:
>>>>>
>>>>> Hello Xenia
>>>>>
>>>>>> On 10/19/22 03:58, Stefano Stabellini wrote:
>>>>>>> On Sat, 15 Oct 2022, Oleksandr Tyshchenko wrote:
>>>>>>>> From: Oleksandr Tyshchenko <[email protected]>
>>>>>>>>
>>>>>>>> Use the same "xen-grant-dma" device concept for the PCI devices
>>>>>>>> behind device-tree based PCI Host controller, but with one
>>>>>>>> modification.
>>>>>>>> Unlike for platform devices, we cannot use generic IOMMU bindings
>>>>>>>> (iommus property), as we need to support more flexible
>>>>>>>> configuration.
>>>>>>>> The problem is that PCI devices under the single PCI Host
>>>>>>>> controller
>>>>>>>> may have the backends running in different Xen domains and thus
>>>>>>>> have
>>>>>>>> different endpoints ID (backend domains ID).
>>>>>>>>
>>>>>>>> So use generic PCI-IOMMU bindings instead (iommu-map/iommu-map-mask
>>>>>>>> properties) which allows us to describe relationship between PCI
>>>>>>>> devices and backend domains ID properly.
>>>>>>>>
>>>>>>>> Signed-off-by: Oleksandr Tyshchenko <[email protected]>
>>>>>>>
>>>>>>> Now that I understood the approach and the reasons for it, I can
>>>>>>> review
>>>>>>> the patch :-)
>>>>>>>
>>>>>>> Please add an example of the bindings in the commit message.
>>>>>>>
>>>>>>>
>>>>>>>> ---
>>>>>>>> Slightly RFC. This is needed to support Xen grant mappings for
>>>>>>>> virtio-pci devices
>>>>>>>> on Arm at some point in the future. The Xen toolstack side is not
>>>>>>>> completely ready yet.
>>>>>>>> Here, for PCI devices we use more flexible way to pass backend
>>>>>>>> domid
>>>>>>>> to the guest
>>>>>>>> than for platform devices.
>>>>>>>>
>>>>>>>> Changes V1 -> V2:
>>>>>>>>       - update commit description
>>>>>>>>       - rebase
>>>>>>>>       - rework to use generic PCI-IOMMU bindings instead of generic
>>>>>>>> IOMMU bindings
>>>>>>>>
>>>>>>>> Previous discussion is at:
>>>>>>>> https://urldefense.com/v3/__https://lore.kernel.org/xen-devel/[email protected]/__;!!GF_29dbcQIUBPA!3-vq7Edm3XfKtD5cnNjnOzDQvuo_XrhJ73yH-nPfqOkGGU0IjLG7R7MR_nAJCAPeOutHRLT44wKYwQwz3SauACie_ZAy$
>>>>>>>>
>>>>>>>>
>>>>>>>> [lore[.]kernel[.]org]
>>>>>>>>
>>>>>>>> Based on:
>>>>>>>> https://urldefense.com/v3/__https://git.kernel.org/pub/scm/linux/kernel/git/xen/tip.git/log/?h=for-linus-6.1__;!!GF_29dbcQIUBPA!3-vq7Edm3XfKtD5cnNjnOzDQvuo_XrhJ73yH-nPfqOkGGU0IjLG7R7MR_nAJCAPeOutHRLT44wKYwQwz3SauAEnMDHAq$
>>>>>>>>
>>>>>>>>
>>>>>>>> [git[.]kernel[.]org]
>>>>>>>> ---
>>>>>>>>     drivers/xen/grant-dma-ops.c | 87
>>>>>>>> ++++++++++++++++++++++++++++++++-----
>>>>>>>>     1 file changed, 76 insertions(+), 11 deletions(-)
>>>>>>>>
>>>>>>>> diff --git a/drivers/xen/grant-dma-ops.c
>>>>>>>> b/drivers/xen/grant-dma-ops.c
>>>>>>>> index daa525df7bdc..b79d9d6ce154 100644
>>>>>>>> --- a/drivers/xen/grant-dma-ops.c
>>>>>>>> +++ b/drivers/xen/grant-dma-ops.c
>>>>>>>> @@ -10,6 +10,7 @@
>>>>>>>>     #include <linux/module.h>
>>>>>>>>     #include <linux/dma-map-ops.h>
>>>>>>>>     #include <linux/of.h>
>>>>>>>> +#include <linux/pci.h>
>>>>>>>>     #include <linux/pfn.h>
>>>>>>>>     #include <linux/xarray.h>
>>>>>>>>     #include <linux/virtio_anchor.h>
>>>>>>>> @@ -292,12 +293,55 @@ static const struct dma_map_ops
>>>>>>>> xen_grant_dma_ops = {
>>>>>>>>         .dma_supported = xen_grant_dma_supported,
>>>>>>>>     };
>>>>>>>>     +static struct device_node *xen_dt_get_pci_host_node(struct
>>>>>>>> device
>>>>>>>> *dev)
>>>>>>>> +{
>>>>>>>> +    struct pci_dev *pdev = to_pci_dev(dev);
>>>>>>>> +    struct pci_bus *bus = pdev->bus;
>>>>>>>> +
>>>>>>>> +    /* Walk up to the root bus to look for PCI Host controller */
>>>>>>>> +    while (!pci_is_root_bus(bus))
>>>>>>>> +        bus = bus->parent;
>>>>>>>> +
>>>>>>>> +    return of_node_get(bus->bridge->parent->of_node);
>>>>>>>> +}
>>>>>>>
>>>>>>> It seems silly that we need to walk the hierachy that way, but I
>>>>>>> couldn't find another way to do it
>>>>>>>
>>>>>>>
>>>>>>>> +static struct device_node *xen_dt_get_node(struct device *dev)
>>>>>>>> +{
>>>>>>>> +    if (dev_is_pci(dev))
>>>>>>>> +        return xen_dt_get_pci_host_node(dev);
>>>>>>>> +
>>>>>>>> +    return of_node_get(dev->of_node);
>>>>>>>> +}
>>>>>>>> +
>>>>>>>> +static int xen_dt_map_id(struct device *dev, struct device_node
>>>>>>>> **iommu_np,
>>>>>>>> +             u32 *sid)
>>>>>>>> +{
>>>>>>>> +    struct pci_dev *pdev = to_pci_dev(dev);
>>>>>>>> +    u32 rid = PCI_DEVID(pdev->bus->number, pdev->devfn);
>>>>>>>> +    struct device_node *host_np;
>>>>>>>> +    int ret;
>>>>>>>> +
>>>>>>>> +    host_np = xen_dt_get_pci_host_node(dev);
>>>>>>>> +    if (!host_np)
>>>>>>>> +        return -ENODEV;
>>>>>>>> +
>>>>>>>> +    ret = of_map_id(host_np, rid, "iommu-map", "iommu-map-mask",
>>>>>>>> iommu_np, sid);
>>>>>>>> +    of_node_put(host_np);
>>>>>>>> +    return ret;
>>>>>>>> +}
>>>>>>>> +
>>>>>>>>     static bool xen_is_dt_grant_dma_device(struct device *dev)
>>>>>>>>     {
>>>>>>>> -    struct device_node *iommu_np;
>>>>>>>> +    struct device_node *iommu_np = NULL;
>>>>>>>>         bool has_iommu;
>>>>>>>>     -    iommu_np = of_parse_phandle(dev->of_node, "iommus", 0);
>>>>>>>> +    if (dev_is_pci(dev)) {
>>>>>>>> +        if (xen_dt_map_id(dev, &iommu_np, NULL))
>>>>>>>> +            return false;
>>>>>>>> +    } else
>>>>>>>> +        iommu_np = of_parse_phandle(dev->of_node, "iommus", 0);
>>>>>>>> +
>>>>>>>>         has_iommu = iommu_np &&
>>>>>>>>                 of_device_is_compatible(iommu_np, "xen,grant-dma");
>>>>>>>>         of_node_put(iommu_np);
>>>>>>>> @@ -307,9 +351,17 @@ static bool xen_is_dt_grant_dma_device(struct
>>>>>>>> device *dev)
>>>>>>>>     bool xen_is_grant_dma_device(struct device *dev)
>>>>>>>>     {
>>>>>>>> +    struct device_node *np;
>>>>>>>> +
>>>>>>>>         /* XXX Handle only DT devices for now */
>>>>>>>> -    if (dev->of_node)
>>>>>>>> -        return xen_is_dt_grant_dma_device(dev);
>>>>>>>> +    np = xen_dt_get_node(dev);
>>>>>>>> +    if (np) {
>>>>>>>> +        bool ret;
>>>>>>>> +
>>>>>>>> +        ret = xen_is_dt_grant_dma_device(dev);
>>>>>>>> +        of_node_put(np);
>>>>>>>> +        return ret;
>>>>>>>> +    }
>>>>>>>
>>>>>>> We don't need to walk the PCI hierachy twice. Maybe we can add the
>>>>>>> of_node check directly to xen_is_dt_grant_dma_device?
>>>>>>>
>>>>>>
>>>>>> I think in general we could pass directly the host bridge device if
>>>>>> dev_is_pci(dev) (which can be retrieved with
>>>>>> pci_get_host_bridge_device(to_pci_dev(dev), and after done with it
>>>>>> pci_put_host_bridge_device(phb)).
>>>>>> So that, xen_is_dt_grant_dma_device() and
>>>>>> xen_dt_grant_init_backend_domid() won't need to discover it
>>>>>> themselves.
>>>>>> This will simplify the code.
>>>>>
>>>>>
>>>>> Good point. I have some remark. Can we use pci_find_host_bridge()
>>>>> instead? This way we don't have to add #include "../pci/pci.h", and
>>>>> have
>>>>> to drop reference afterwards.
>>>>>
>>>>> With that xen_dt_get_pci_host_node() will became the following:
>>>>>
>>>>>
>>>>> static struct device_node *xen_dt_get_pci_host_node(struct device
>>>>> *dev)
>>>>> {
>>>>>       struct pci_host_bridge *bridge =
>>>>> pci_find_host_bridge(to_pci_dev(dev)->bus);
>>>>>
>>>>>       return of_node_get(bridge->dev.parent->of_node);
>>>>> }
>>>>>
>>>>
>>>> You are right. I prefer your version instead of the above.
>>>
>>>
>>> ok, thanks
>>>
>>>
>>>>
>>>>
>>>>>
>>>>> With Stefano's suggestion, we won't walk the PCI hierarchy twice when
>>>>> executing xen_is_grant_dma_device() for PCI device:
>>>>>
>>>>> xen_is_grant_dma_device() -> xen_is_dt_grant_dma_device() ->
>>>>> xen_dt_map_id() -> xen_dt_get_pci_host_node()
>>>>>
>>>>>
>>>>> What do you think?
>>>>>
>>>>
>>>> I was thinking passing the device_node along with the device in the
>>>> function arguments. More specifically, of doing this (not tested, just
>>>> an idea):
>>>>
>>>> bool xen_is_grant_dma_device(struct device *dev)
>>>> {
>>>>      struct device_node *np;
>>>>      bool has_iommu = false;
>>>>
>>>>      /* XXX Handle only DT devices for now */
>>>>      np = xen_dt_get_node(dev);
>>>>      if (np)
>>>>          has_iommu = xen_is_dt_grant_dma_device(dev, np);
>>>>      of_node_put(np);
>>>>      return has_iommu;
>>>> }
>>>>
>>>> static bool xen_is_dt_grant_dma_device(struct device *dev,
>>>>                                         struct device_node *np)
>>>> {
>>>>      struct device_node *iommu_np = NULL;
>>>>      bool has_iommu;
>>>>
>>>>      if (dev_is_pci(dev)) {
>>>>          struct pci_dev *pdev = to_pci_dev(dev);
>>>>      u32 id = PCI_DEVID(pdev->bus->number, pdev->devfn);
>>>>          of_map_id(np, id, "iommu-map", "iommu-map-mask", &iommu_np,
>>>> NULL);
>>>>      } else {
>>>>          iommu_np = of_parse_phandle(np, "iommus", 0);
>>>>      }
>>>>
>>>>      has_iommu = iommu_np && of_device_is_compatible(iommu_np,
>>>> "xen,grant-dma");
>>>>      of_node_put(iommu_np);
>>>>
>>>>      return has_iommu;
>>>> }
>>>
>>>
>>> I got it.
>>>
>>> xen_is_grant_dma_device() for V3 won't call xen_dt_get_node(), but call
>>> xen_is_dt_grant_dma_device() directly.
>>>
>>> static bool xen_is_dt_grant_dma_device(struct device *dev)
>>> {
>>>    struct device_node *iommu_np = NULL;
>>>    bool has_iommu;
>>>
>>>    if (dev_is_pci(dev)) {
>>>         if (xen_dt_map_id(dev, &iommu_np, NULL))
>>>             return false;
>>>    } else if (dev->of_node)
>>>         iommu_np = of_parse_phandle(dev->of_node, "iommus", 0);
>>>    else
>>>         return false;
>>>
>>>    has_iommu = iommu_np &&
>>>             of_device_is_compatible(iommu_np, "xen,grant-dma");
>>>    of_node_put(iommu_np);
>>>
>>>    return has_iommu;
>>> }
>>>
>>> bool xen_is_grant_dma_device(struct device *dev)
>>> {
>>>    /* XXX Handle only DT devices for now */
>>>    return xen_is_dt_grant_dma_device(dev);
>>> }
>>>
>>>
>>
>> Ok. One difference, that I see from the previous, is that here you
>> don't use the dynamic interface when you access the dev->of_node
>> (of_node_get/of_node_put). Before, this was guarded through the
>> external xen_dt_get_node().
>>
>> I suspect that the same needs to be done for the function
>> xen_grant_setup_dma_ops(). There, also, the code walks up to the root
>> bus twice.
>
>
> Hmm, xen_dt_grant_init_backend_domid() should only be called if we deal
> with device-tree based device.
>
> I think you are completely right, thanks!
>
> In order to address both your comments, I think I need to rework the
> code (taking into the account your example with xen_is_dt_grant_dma_device()
>
> provided a few letters ago and extrapolate this example to
> xen_dt_grant_init_backend_domid()). Below the patch (not tested) which
> seems to address both your comments (also I dropped
>
> xen_dt_map_id() and squashed xen_dt_get_pci_host_node() with
> xen_dt_get_node()).
>
>
> diff --git a/drivers/xen/grant-dma-ops.c b/drivers/xen/grant-dma-ops.c
> index daa525df7bdc..dae24dbd2ef7 100644
> --- a/drivers/xen/grant-dma-ops.c
> +++ b/drivers/xen/grant-dma-ops.c
> @@ -10,6 +10,7 @@
> #include <linux/module.h>
> #include <linux/dma-map-ops.h>
> #include <linux/of.h>
> +#include <linux/pci.h>
> #include <linux/pfn.h>
> #include <linux/xarray.h>
> #include <linux/virtio_anchor.h>
> @@ -292,12 +293,33 @@ static const struct dma_map_ops xen_grant_dma_ops = {
>         .dma_supported = xen_grant_dma_supported,
> };
>
> -static bool xen_is_dt_grant_dma_device(struct device *dev)
> +static struct device_node *xen_dt_get_node(struct device *dev)
> {
> -       struct device_node *iommu_np;
> +       if (dev_is_pci(dev)) {
> +               struct pci_dev *pdev = to_pci_dev(dev);
> +               struct pci_host_bridge *bridge =
> pci_find_host_bridge(pdev->bus);
> +
> +               return of_node_get(bridge->dev.parent->of_node);
> +       }
> +
> +       return of_node_get(dev->of_node);
> +}
> +

It does not seem right to me to expose the struct pci_host_bridge (which
we would need to check if it is null by the way). I would prefer your
version for the above i.e
static struct device_node *xen_dt_get_node(struct device *dev)
{
if (dev_is_pci(dev)) {
struct pci_bus *bus = to_pci_dev(dev)->bus;

/* Walk up to the root bus to look for PCI Host controller */
while (!pci_is_root_bus(bus))
bus = bus->parent;
return of_node_get(bus->bridge->parent->of_node);
}

return of_node_get(dev->of_node);
}

> +static bool xen_is_dt_grant_dma_device(struct device *dev,
> +                                       struct device_node *np)
> +{
> +       struct device_node *iommu_np = NULL;
>         bool has_iommu;
>
> -       iommu_np = of_parse_phandle(dev->of_node, "iommus", 0);
> +       if (dev_is_pci(dev)) {
> +               struct pci_dev *pdev = to_pci_dev(dev);
> +               u32 rid = PCI_DEVID(pdev->bus->number, pdev->devfn);
> +
> +               if (of_map_id(np, rid, "iommu-map", "iommu-map-mask",
> &iommu_np, NULL))
> +                       return false;
> +       } else
> +               iommu_np = of_parse_phandle(np, "iommus", 0);
> +
>         has_iommu = iommu_np &&
>                     of_device_is_compatible(iommu_np, "xen,grant-dma");
>         of_node_put(iommu_np);
> @@ -307,9 +329,17 @@ static bool xen_is_dt_grant_dma_device(struct
> device *dev)
>
> bool xen_is_grant_dma_device(struct device *dev)
> {
> +       struct device_node *np;
> +
>         /* XXX Handle only DT devices for now */
> -       if (dev->of_node)
> -               return xen_is_dt_grant_dma_device(dev);
> +       np = xen_dt_get_node(dev);
> +       if (np) {
> +               bool ret;
> +
> +               ret = xen_is_dt_grant_dma_device(dev, np);
> +               of_node_put(np);
> +               return ret;
> +       }
>
>         return false;
> }

> @@ -323,14 +353,26 @@ bool xen_virtio_mem_acc(struct virtio_device *dev)
> }
>
> static int xen_dt_grant_init_backend_domid(struct device *dev,
> +                                          struct device_node *np,
>                                            struct xen_grant_dma_data *data)
> {
> -       struct of_phandle_args iommu_spec;
> +       struct of_phandle_args iommu_spec = { .args_count = 1 };
>
> -       if (of_parse_phandle_with_args(dev->of_node, "iommus",
> "#iommu-cells",
> -                       0, &iommu_spec)) {
> -               dev_err(dev, "Cannot parse iommus property\n");
> -               return -ESRCH;
> +       if (dev_is_pci(dev)) {
> +               struct pci_dev *pdev = to_pci_dev(dev);
> +               u32 rid = PCI_DEVID(pdev->bus->number, pdev->devfn);
> +
> +               if (of_map_id(np, rid, "iommu-map", "iommu-map-mask",
> &iommu_spec.np,
> +                               iommu_spec.args)) {
> +                       dev_err(dev, "Cannot translate ID\n");
> +                       return -ESRCH;
> +               }
> +       } else {
> +               if (of_parse_phandle_with_args(np, "iommus", "#iommu-cells",
> +                               0, &iommu_spec)) {
> +                       dev_err(dev, "Cannot parse iommus property\n");
> +                       return -ESRCH;
> +               }
>         }
>

IMO, instead of passing struct xen_grant_dma_data *data to
xen_dt_grant_init_backend_domid(), you could pass domid_t *backend_domid
(e.g xen_dt_grant_init_backend_domid(dev, np, &data->backend_domid)).
I think this way the internal struct xen_grant_dma_datain is manipulated
in a single place and xen_dt_grant_init_backend_domid() does not depend
on it.

>         if (!of_device_is_compatible(iommu_spec.np, "xen,grant-dma") ||
> @@ -354,6 +396,7 @@ static int xen_dt_grant_init_backend_domid(struct
> device *dev,
> void xen_grant_setup_dma_ops(struct device *dev)
> {
>         struct xen_grant_dma_data *data;
> +       struct device_node *np;
>
>         data = find_xen_grant_dma_data(dev);
>         if (data) {
> @@ -365,8 +408,13 @@ void xen_grant_setup_dma_ops(struct device *dev)
>         if (!data)
>                 goto err;
>
> -       if (dev->of_node) {
> -               if (xen_dt_grant_init_backend_domid(dev, data))
> +       np = xen_dt_get_node(dev);
> +       if (np) {
> +               int ret;
> +
> +               ret = xen_dt_grant_init_backend_domid(dev, np, data);
> +               of_node_put(np);
> +               if (ret)
>                         goto err;
>         } else if (IS_ENABLED(CONFIG_XEN_VIRTIO_FORCE_GRANT)) {
>                 dev_info(dev, "Using dom0 as backend\n");
>
>
> Does it look ok now?

That is what I had in mind. I do not know if Stefano agrees with this
approach.

>>
>>
>>>>
>>>> I 'm wondering ... is it possible for the host bridge device node to
>>>> have the iommus property set? meaning that all of its pci devs will
>>>> have the same backend?
>>>
>>> Good question. I think, it is possible... This is technically what V1 is
>>> doing.
>>>
>>>
>>> Are you asking because to support "iommus" for PCI devices as well to
>>> describe that use-case with all PCI devices having the same endpoint ID
>>> (backend ID)?
>>> If yes, I think, this could be still described by "iommu-map" property,
>>> something like that (if we don't want to describe mapping for each PCI
>>> device one-by-one).
>>>
>>> iommu-map = <0x0 &iommu X 0x1>;
>>>
>>> iommu-map-mask = <0x0>;
>>>
>>> where the X is backend ID.
>>>
>>>
>>> It feels to me that it should be written down somewhere that for
>>> platform devices we expect "iommus" and for PCI devices we expect
>>> "iommu-map/iommu-map-mask" to be present.
>>
>> Thanks for the clarification, now I got it. Yes I agree.
>
>
> ok, good
>
>
>>
>>>>
>>>>
>>>>>>
>>>>>>>
>>>>>>>>         return false;
>>>>>>>>     }
>>>>>>>> @@ -325,12 +377,19 @@ bool xen_virtio_mem_acc(struct virtio_device
>>>>>>>> *dev)
>>>>>>>>     static int xen_dt_grant_init_backend_domid(struct device *dev,
>>>>>>>>                            struct xen_grant_dma_data *data)
>>>>>>>>     {
>>>>>>>> -    struct of_phandle_args iommu_spec;
>>>>>>>> +    struct of_phandle_args iommu_spec = { .args_count = 1 };
>>>>>>>>     -    if (of_parse_phandle_with_args(dev->of_node, "iommus",
>>>>>>>> "#iommu-cells",
>>>>>>>> -            0, &iommu_spec)) {
>>>>>>>> -        dev_err(dev, "Cannot parse iommus property\n");
>>>>>>>> -        return -ESRCH;
>>>>>>>> +    if (dev_is_pci(dev)) {
>>>>>>>> +        if (xen_dt_map_id(dev, &iommu_spec.np, iommu_spec.args)) {
>>>>>>>> +            dev_err(dev, "Cannot translate ID\n");
>>>>>>>> +            return -ESRCH;
>>>>>>>> +        }
>>>>>>>> +    } else {
>>>>>>>> +        if (of_parse_phandle_with_args(dev->of_node, "iommus",
>>>>>>>> "#iommu-cells",
>>>>>>>> +                0, &iommu_spec)) {
>>>>>>>> +            dev_err(dev, "Cannot parse iommus property\n");
>>>>>>>> +            return -ESRCH;
>>>>>>>> +        }
>>>>>>>>         }
>>>>>>>>           if (!of_device_is_compatible(iommu_spec.np,
>>>>>>>> "xen,grant-dma") ||
>>>>>>>> @@ -354,6 +413,7 @@ static int
>>>>>>>> xen_dt_grant_init_backend_domid(struct device *dev,
>>>>>>>>     void xen_grant_setup_dma_ops(struct device *dev)
>>>>>>>>     {
>>>>>>>>         struct xen_grant_dma_data *data;
>>>>>>>> +    struct device_node *np;
>>>>>>>>           data = find_xen_grant_dma_data(dev);
>>>>>>>>         if (data) {
>>>>>>>> @@ -365,8 +425,13 @@ void xen_grant_setup_dma_ops(struct device
>>>>>>>> *dev)
>>>>>>>>         if (!data)
>>>>>>>>             goto err;
>>>>>>>>     -    if (dev->of_node) {
>>>>>>>> -        if (xen_dt_grant_init_backend_domid(dev, data))
>>>>>>>> +    np = xen_dt_get_node(dev);
>>>>>>>> +    if (np) {
>>>>>>>> +        int ret;
>>>>>>>> +
>>>>>>>> +        ret = xen_dt_grant_init_backend_domid(dev, data);
>>>>>>>> +        of_node_put(np);
>>>>>>>> +        if (ret)
>>>>>>>>                 goto err;
>>>>>>>>         } else if (IS_ENABLED(CONFIG_XEN_VIRTIO_FORCE_GRANT)) {
>>>>>>>>             dev_info(dev, "Using dom0 as backend\n");
>>>>>>>> --
>>>>>>>> 2.25.1
>>>>>>>>
>>>>>>>
>>>>>>
>>>>
>>

--
Xenia

2022-10-21 06:49:20

by Oleksandr Tyshchenko

[permalink] [raw]

Subject: Re: [PATCH V2] xen/virtio: Handle PCI devices which Host controller is described in DT

On 21.10.22 09:08, Xenia Ragiadakou wrote:

Hello Xenia

> On 10/20/22 23:07, Oleksandr Tyshchenko wrote:
> Hi Oleksandr
>>
>> On 20.10.22 21:11, Xenia Ragiadakou wrote:
>>
>> Hello Xenia
>>
>>
>>> On 10/20/22 17:12, Oleksandr Tyshchenko wrote:
>>>>
>>>> On 20.10.22 11:24, Xenia Ragiadakou wrote:
>>>>> On 10/19/22 22:41, Oleksandr Tyshchenko wrote:
>>>>>
>>>>> Hi Oleksandr
>>>>
>>>>
>>>> Hello Xenia
>>>>
>>>>
>>>>>
>>>>>>
>>>>>> On 19.10.22 11:47, Xenia Ragiadakou wrote:
>>>>>>
>>>>>> Hello Xenia
>>>>>>
>>>>>>> On 10/19/22 03:58, Stefano Stabellini wrote:
>>>>>>>> On Sat, 15 Oct 2022, Oleksandr Tyshchenko wrote:
>>>>>>>>> From: Oleksandr Tyshchenko <[email protected]>
>>>>>>>>>
>>>>>>>>> Use the same "xen-grant-dma" device concept for the PCI devices
>>>>>>>>> behind device-tree based PCI Host controller, but with one
>>>>>>>>> modification.
>>>>>>>>> Unlike for platform devices, we cannot use generic IOMMU bindings
>>>>>>>>> (iommus property), as we need to support more flexible
>>>>>>>>> configuration.
>>>>>>>>> The problem is that PCI devices under the single PCI Host
>>>>>>>>> controller
>>>>>>>>> may have the backends running in different Xen domains and thus
>>>>>>>>> have
>>>>>>>>> different endpoints ID (backend domains ID).
>>>>>>>>>
>>>>>>>>> So use generic PCI-IOMMU bindings instead
>>>>>>>>> (iommu-map/iommu-map-mask
>>>>>>>>> properties) which allows us to describe relationship between PCI
>>>>>>>>> devices and backend domains ID properly.
>>>>>>>>>
>>>>>>>>> Signed-off-by: Oleksandr Tyshchenko
>>>>>>>>> <[email protected]>
>>>>>>>>
>>>>>>>> Now that I understood the approach and the reasons for it, I can
>>>>>>>> review
>>>>>>>> the patch :-)
>>>>>>>>
>>>>>>>> Please add an example of the bindings in the commit message.
>>>>>>>>
>>>>>>>>
>>>>>>>>> ---
>>>>>>>>> Slightly RFC. This is needed to support Xen grant mappings for
>>>>>>>>> virtio-pci devices
>>>>>>>>> on Arm at some point in the future. The Xen toolstack side is not
>>>>>>>>> completely ready yet.
>>>>>>>>> Here, for PCI devices we use more flexible way to pass backend
>>>>>>>>> domid
>>>>>>>>> to the guest
>>>>>>>>> than for platform devices.
>>>>>>>>>
>>>>>>>>> Changes V1 -> V2:
>>>>>>>>>        - update commit description
>>>>>>>>>        - rebase
>>>>>>>>>        - rework to use generic PCI-IOMMU bindings instead of
>>>>>>>>> generic
>>>>>>>>> IOMMU bindings
>>>>>>>>>
>>>>>>>>> Previous discussion is at:
>>>>>>>>> https://urldefense.com/v3/__https://lore.kernel.org/xen-devel/[email protected]/__;!!GF_29dbcQIUBPA!3-vq7Edm3XfKtD5cnNjnOzDQvuo_XrhJ73yH-nPfqOkGGU0IjLG7R7MR_nAJCAPeOutHRLT44wKYwQwz3SauACie_ZAy$
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> [lore[.]kernel[.]org]
>>>>>>>>>
>>>>>>>>> Based on:
>>>>>>>>> https://urldefense.com/v3/__https://git.kernel.org/pub/scm/linux/kernel/git/xen/tip.git/log/?h=for-linus-6.1__;!!GF_29dbcQIUBPA!3-vq7Edm3XfKtD5cnNjnOzDQvuo_XrhJ73yH-nPfqOkGGU0IjLG7R7MR_nAJCAPeOutHRLT44wKYwQwz3SauAEnMDHAq$
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> [git[.]kernel[.]org]
>>>>>>>>> ---
>>>>>>>>>      drivers/xen/grant-dma-ops.c | 87
>>>>>>>>> ++++++++++++++++++++++++++++++++-----
>>>>>>>>>      1 file changed, 76 insertions(+), 11 deletions(-)
>>>>>>>>>
>>>>>>>>> diff --git a/drivers/xen/grant-dma-ops.c
>>>>>>>>> b/drivers/xen/grant-dma-ops.c
>>>>>>>>> index daa525df7bdc..b79d9d6ce154 100644
>>>>>>>>> --- a/drivers/xen/grant-dma-ops.c
>>>>>>>>> +++ b/drivers/xen/grant-dma-ops.c
>>>>>>>>> @@ -10,6 +10,7 @@
>>>>>>>>>      #include <linux/module.h>
>>>>>>>>>      #include <linux/dma-map-ops.h>
>>>>>>>>>      #include <linux/of.h>
>>>>>>>>> +#include <linux/pci.h>
>>>>>>>>>      #include <linux/pfn.h>
>>>>>>>>>      #include <linux/xarray.h>
>>>>>>>>>      #include <linux/virtio_anchor.h>
>>>>>>>>> @@ -292,12 +293,55 @@ static const struct dma_map_ops
>>>>>>>>> xen_grant_dma_ops = {
>>>>>>>>>          .dma_supported = xen_grant_dma_supported,
>>>>>>>>>      };
>>>>>>>>>      +static struct device_node *xen_dt_get_pci_host_node(struct
>>>>>>>>> device
>>>>>>>>> *dev)
>>>>>>>>> +{
>>>>>>>>> +    struct pci_dev *pdev = to_pci_dev(dev);
>>>>>>>>> +    struct pci_bus *bus = pdev->bus;
>>>>>>>>> +
>>>>>>>>> +    /* Walk up to the root bus to look for PCI Host
>>>>>>>>> controller */
>>>>>>>>> +    while (!pci_is_root_bus(bus))
>>>>>>>>> +        bus = bus->parent;
>>>>>>>>> +
>>>>>>>>> +    return of_node_get(bus->bridge->parent->of_node);
>>>>>>>>> +}
>>>>>>>>
>>>>>>>> It seems silly that we need to walk the hierachy that way, but I
>>>>>>>> couldn't find another way to do it
>>>>>>>>
>>>>>>>>
>>>>>>>>> +static struct device_node *xen_dt_get_node(struct device *dev)
>>>>>>>>> +{
>>>>>>>>> +    if (dev_is_pci(dev))
>>>>>>>>> +        return xen_dt_get_pci_host_node(dev);
>>>>>>>>> +
>>>>>>>>> +    return of_node_get(dev->of_node);
>>>>>>>>> +}
>>>>>>>>> +
>>>>>>>>> +static int xen_dt_map_id(struct device *dev, struct device_node
>>>>>>>>> **iommu_np,
>>>>>>>>> +             u32 *sid)
>>>>>>>>> +{
>>>>>>>>> +    struct pci_dev *pdev = to_pci_dev(dev);
>>>>>>>>> +    u32 rid = PCI_DEVID(pdev->bus->number, pdev->devfn);
>>>>>>>>> +    struct device_node *host_np;
>>>>>>>>> +    int ret;
>>>>>>>>> +
>>>>>>>>> +    host_np = xen_dt_get_pci_host_node(dev);
>>>>>>>>> +    if (!host_np)
>>>>>>>>> +        return -ENODEV;
>>>>>>>>> +
>>>>>>>>> +    ret = of_map_id(host_np, rid, "iommu-map", "iommu-map-mask",
>>>>>>>>> iommu_np, sid);
>>>>>>>>> +    of_node_put(host_np);
>>>>>>>>> +    return ret;
>>>>>>>>> +}
>>>>>>>>> +
>>>>>>>>>      static bool xen_is_dt_grant_dma_device(struct device *dev)
>>>>>>>>>      {
>>>>>>>>> -    struct device_node *iommu_np;
>>>>>>>>> +    struct device_node *iommu_np = NULL;
>>>>>>>>>          bool has_iommu;
>>>>>>>>>      -    iommu_np = of_parse_phandle(dev->of_node, "iommus", 0);
>>>>>>>>> +    if (dev_is_pci(dev)) {
>>>>>>>>> +        if (xen_dt_map_id(dev, &iommu_np, NULL))
>>>>>>>>> +            return false;
>>>>>>>>> +    } else
>>>>>>>>> +        iommu_np = of_parse_phandle(dev->of_node, "iommus", 0);
>>>>>>>>> +
>>>>>>>>>          has_iommu = iommu_np &&
>>>>>>>>>                  of_device_is_compatible(iommu_np,
>>>>>>>>> "xen,grant-dma");
>>>>>>>>>          of_node_put(iommu_np);
>>>>>>>>> @@ -307,9 +351,17 @@ static bool
>>>>>>>>> xen_is_dt_grant_dma_device(struct
>>>>>>>>> device *dev)
>>>>>>>>>      bool xen_is_grant_dma_device(struct device *dev)
>>>>>>>>>      {
>>>>>>>>> +    struct device_node *np;
>>>>>>>>> +
>>>>>>>>>          /* XXX Handle only DT devices for now */
>>>>>>>>> -    if (dev->of_node)
>>>>>>>>> -        return xen_is_dt_grant_dma_device(dev);
>>>>>>>>> +    np = xen_dt_get_node(dev);
>>>>>>>>> +    if (np) {
>>>>>>>>> +        bool ret;
>>>>>>>>> +
>>>>>>>>> +        ret = xen_is_dt_grant_dma_device(dev);
>>>>>>>>> +        of_node_put(np);
>>>>>>>>> +        return ret;
>>>>>>>>> +    }
>>>>>>>>
>>>>>>>> We don't need to walk the PCI hierachy twice. Maybe we can add the
>>>>>>>> of_node check directly to xen_is_dt_grant_dma_device?
>>>>>>>>
>>>>>>>
>>>>>>> I think in general we could pass directly the host bridge device if
>>>>>>> dev_is_pci(dev) (which can be retrieved with
>>>>>>> pci_get_host_bridge_device(to_pci_dev(dev), and after done with it
>>>>>>> pci_put_host_bridge_device(phb)).
>>>>>>> So that, xen_is_dt_grant_dma_device() and
>>>>>>> xen_dt_grant_init_backend_domid() won't need to discover it
>>>>>>> themselves.
>>>>>>> This will simplify the code.
>>>>>>
>>>>>>
>>>>>> Good point. I have some remark. Can we use pci_find_host_bridge()
>>>>>> instead? This way we don't have to add #include "../pci/pci.h", and
>>>>>> have
>>>>>> to drop reference afterwards.
>>>>>>
>>>>>> With that xen_dt_get_pci_host_node() will became the following:
>>>>>>
>>>>>>
>>>>>> static struct device_node *xen_dt_get_pci_host_node(struct device
>>>>>> *dev)
>>>>>> {
>>>>>>        struct pci_host_bridge *bridge =
>>>>>> pci_find_host_bridge(to_pci_dev(dev)->bus);
>>>>>>
>>>>>>        return of_node_get(bridge->dev.parent->of_node);
>>>>>> }
>>>>>>
>>>>>
>>>>> You are right. I prefer your version instead of the above.
>>>>
>>>>
>>>> ok, thanks
>>>>
>>>>
>>>>>
>>>>>
>>>>>>
>>>>>> With Stefano's suggestion, we won't walk the PCI hierarchy twice
>>>>>> when
>>>>>> executing xen_is_grant_dma_device() for PCI device:
>>>>>>
>>>>>> xen_is_grant_dma_device() -> xen_is_dt_grant_dma_device() ->
>>>>>> xen_dt_map_id() -> xen_dt_get_pci_host_node()
>>>>>>
>>>>>>
>>>>>> What do you think?
>>>>>>
>>>>>
>>>>> I was thinking passing the device_node along with the device in the
>>>>> function arguments. More specifically, of doing this (not tested,
>>>>> just
>>>>> an idea):
>>>>>
>>>>> bool xen_is_grant_dma_device(struct device *dev)
>>>>> {
>>>>>       struct device_node *np;
>>>>>       bool has_iommu = false;
>>>>>
>>>>>       /* XXX Handle only DT devices for now */
>>>>>       np = xen_dt_get_node(dev);
>>>>>       if (np)
>>>>>           has_iommu = xen_is_dt_grant_dma_device(dev, np);
>>>>>       of_node_put(np);
>>>>>       return has_iommu;
>>>>> }
>>>>>
>>>>> static bool xen_is_dt_grant_dma_device(struct device *dev,
>>>>>                                          struct device_node *np)
>>>>> {
>>>>>       struct device_node *iommu_np = NULL;
>>>>>       bool has_iommu;
>>>>>
>>>>>       if (dev_is_pci(dev)) {
>>>>>           struct pci_dev *pdev = to_pci_dev(dev);
>>>>>       u32 id = PCI_DEVID(pdev->bus->number, pdev->devfn);
>>>>>           of_map_id(np, id, "iommu-map", "iommu-map-mask", &iommu_np,
>>>>> NULL);
>>>>>       } else {
>>>>>           iommu_np = of_parse_phandle(np, "iommus", 0);
>>>>>       }
>>>>>
>>>>>       has_iommu = iommu_np && of_device_is_compatible(iommu_np,
>>>>> "xen,grant-dma");
>>>>>       of_node_put(iommu_np);
>>>>>
>>>>>       return has_iommu;
>>>>> }
>>>>
>>>>
>>>> I got it.
>>>>
>>>> xen_is_grant_dma_device() for V3 won't call xen_dt_get_node(), but
>>>> call
>>>> xen_is_dt_grant_dma_device() directly.
>>>>
>>>> static bool xen_is_dt_grant_dma_device(struct device *dev)
>>>> {
>>>>       struct device_node *iommu_np = NULL;
>>>>       bool has_iommu;
>>>>
>>>>       if (dev_is_pci(dev)) {
>>>>            if (xen_dt_map_id(dev, &iommu_np, NULL))
>>>>                return false;
>>>>       } else if (dev->of_node)
>>>>            iommu_np = of_parse_phandle(dev->of_node, "iommus", 0);
>>>>       else
>>>>            return false;
>>>>
>>>>       has_iommu = iommu_np &&
>>>>                of_device_is_compatible(iommu_np, "xen,grant-dma");
>>>>       of_node_put(iommu_np);
>>>>
>>>>       return has_iommu;
>>>> }
>>>>
>>>> bool xen_is_grant_dma_device(struct device *dev)
>>>> {
>>>>       /* XXX Handle only DT devices for now */
>>>>       return xen_is_dt_grant_dma_device(dev);
>>>> }
>>>>
>>>>
>>>
>>> Ok. One difference, that I see from the previous, is that here you
>>> don't use the dynamic interface when you access the dev->of_node
>>> (of_node_get/of_node_put). Before, this was guarded through the
>>> external xen_dt_get_node().
>>>
>>> I suspect that the same needs to be done for the function
>>> xen_grant_setup_dma_ops(). There, also, the code walks up to the root
>>> bus twice.
>>
>>
>> Hmm, xen_dt_grant_init_backend_domid() should only be called if we deal
>> with device-tree based device.
>>
>> I think you are completely right, thanks!
>>
>> In order to address both your comments, I think I need to rework the
>> code (taking into the account your example with
>> xen_is_dt_grant_dma_device()
>>
>> provided a few letters ago and extrapolate this example to
>> xen_dt_grant_init_backend_domid()). Below the patch (not tested) which
>> seems to address both your comments (also I dropped
>>
>> xen_dt_map_id() and squashed xen_dt_get_pci_host_node() with
>> xen_dt_get_node()).
>>
>>
>> diff --git a/drivers/xen/grant-dma-ops.c b/drivers/xen/grant-dma-ops.c
>> index daa525df7bdc..dae24dbd2ef7 100644
>> --- a/drivers/xen/grant-dma-ops.c
>> +++ b/drivers/xen/grant-dma-ops.c
>> @@ -10,6 +10,7 @@
>> #include <linux/module.h>
>> #include <linux/dma-map-ops.h>
>> #include <linux/of.h>
>> +#include <linux/pci.h>
>> #include <linux/pfn.h>
>> #include <linux/xarray.h>
>> #include <linux/virtio_anchor.h>
>> @@ -292,12 +293,33 @@ static const struct dma_map_ops
>> xen_grant_dma_ops = {
>>         .dma_supported = xen_grant_dma_supported,
>> };
>>
>> -static bool xen_is_dt_grant_dma_device(struct device *dev)
>> +static struct device_node *xen_dt_get_node(struct device *dev)
>> {
>> -       struct device_node *iommu_np;
>> +       if (dev_is_pci(dev)) {
>> +               struct pci_dev *pdev = to_pci_dev(dev);
>> +               struct pci_host_bridge *bridge =
>> pci_find_host_bridge(pdev->bus);
>> +
>> +               return of_node_get(bridge->dev.parent->of_node);
>> +       }
>> +
>> +       return of_node_get(dev->of_node);
>> +}
>> +
>
> It does not seem right to me to expose the struct pci_host_bridge
> (which we would need to check if it is null by the way). I would
> prefer your version for the above i.e
> static struct device_node *xen_dt_get_node(struct device *dev)
> {
>     if (dev_is_pci(dev)) {
>         struct pci_bus *bus = to_pci_dev(dev)->bus;
>
>         /* Walk up to the root bus to look for PCI Host controller */
>         while (!pci_is_root_bus(bus))
>             bus = bus->parent;
>         return of_node_get(bus->bridge->parent->of_node);
>     }
>
>     return of_node_get(dev->of_node);
> }

ok, will return it back

>
>> +static bool xen_is_dt_grant_dma_device(struct device *dev,
>> +                                       struct device_node *np)
>> +{
>> +       struct device_node *iommu_np = NULL;
>>         bool has_iommu;
>>
>> -       iommu_np = of_parse_phandle(dev->of_node, "iommus", 0);
>> +       if (dev_is_pci(dev)) {
>> +               struct pci_dev *pdev = to_pci_dev(dev);
>> +               u32 rid = PCI_DEVID(pdev->bus->number, pdev->devfn);
>> +
>> +               if (of_map_id(np, rid, "iommu-map", "iommu-map-mask",
>> &iommu_np, NULL))
>> +                       return false;
>> +       } else
>> +               iommu_np = of_parse_phandle(np, "iommus", 0);
>> +
>>         has_iommu = iommu_np &&
>>                     of_device_is_compatible(iommu_np,
>> "xen,grant-dma");
>>         of_node_put(iommu_np);
>> @@ -307,9 +329,17 @@ static bool xen_is_dt_grant_dma_device(struct
>> device *dev)
>>
>> bool xen_is_grant_dma_device(struct device *dev)
>> {
>> +       struct device_node *np;
>> +
>>         /* XXX Handle only DT devices for now */
>> -       if (dev->of_node)
>> -               return xen_is_dt_grant_dma_device(dev);
>> +       np = xen_dt_get_node(dev);
>> +       if (np) {
>> +               bool ret;
>> +
>> +               ret = xen_is_dt_grant_dma_device(dev, np);
>> +               of_node_put(np);
>> +               return ret;
>> +       }
>>
>>         return false;
>> }
>
>> @@ -323,14 +353,26 @@ bool xen_virtio_mem_acc(struct virtio_device *dev)
>> }
>>
>> static int xen_dt_grant_init_backend_domid(struct device *dev,
>> +                                          struct device_node *np,
>>                                            struct
>> xen_grant_dma_data *data)
>> {
>> -       struct of_phandle_args iommu_spec;
>> +       struct of_phandle_args iommu_spec = { .args_count = 1 };
>>
>> -       if (of_parse_phandle_with_args(dev->of_node, "iommus",
>> "#iommu-cells",
>> -                       0, &iommu_spec)) {
>> -               dev_err(dev, "Cannot parse iommus property\n");
>> -               return -ESRCH;
>> +       if (dev_is_pci(dev)) {
>> +               struct pci_dev *pdev = to_pci_dev(dev);
>> +               u32 rid = PCI_DEVID(pdev->bus->number, pdev->devfn);
>> +
>> +               if (of_map_id(np, rid, "iommu-map", "iommu-map-mask",
>> &iommu_spec.np,
>> +                               iommu_spec.args)) {
>> +                       dev_err(dev, "Cannot translate ID\n");
>> +                       return -ESRCH;
>> +               }
>> +       } else {
>> +               if (of_parse_phandle_with_args(np, "iommus",
>> "#iommu-cells",
>> +                               0, &iommu_spec)) {
>> +                       dev_err(dev, "Cannot parse iommus property\n");
>> +                       return -ESRCH;
>> +               }
>>         }
>>
>
> IMO, instead of passing struct xen_grant_dma_data *data to
> xen_dt_grant_init_backend_domid(), you could pass domid_t
> *backend_domid (e.g xen_dt_grant_init_backend_domid(dev, np,
> &data->backend_domid)).
> I think this way the internal struct xen_grant_dma_datain is
> manipulated in a single place and xen_dt_grant_init_backend_domid()
> does not depend on it.

Although I think it is not directly related to current patch, I agree we
could make this change as we touch the list of arguments for
xen_dt_grant_init_backend_domid() anyway.

>
>
>>         if (!of_device_is_compatible(iommu_spec.np,
>> "xen,grant-dma") ||
>> @@ -354,6 +396,7 @@ static int xen_dt_grant_init_backend_domid(struct
>> device *dev,
>> void xen_grant_setup_dma_ops(struct device *dev)
>> {
>>         struct xen_grant_dma_data *data;
>> +       struct device_node *np;
>>
>>         data = find_xen_grant_dma_data(dev);
>>         if (data) {
>> @@ -365,8 +408,13 @@ void xen_grant_setup_dma_ops(struct device *dev)
>>         if (!data)
>>                 goto err;
>>
>> -       if (dev->of_node) {
>> -               if (xen_dt_grant_init_backend_domid(dev, data))
>> +       np = xen_dt_get_node(dev);
>> +       if (np) {
>> +               int ret;
>> +
>> +               ret = xen_dt_grant_init_backend_domid(dev, np, data);
>> +               of_node_put(np);
>> +               if (ret)
>>                         goto err;
>>         } else if (IS_ENABLED(CONFIG_XEN_VIRTIO_FORCE_GRANT)) {
>>                 dev_info(dev, "Using dom0 as backend\n");
>>
>>
>> Does it look ok now?
>
> That is what I had in mind.

Great, thanks!

> I do not know if Stefano agrees with this approach.

We will see

>
>>>
>>>
>>>>>
>>>>> I 'm wondering ... is it possible for the host bridge device node to
>>>>> have the iommus property set? meaning that all of its pci devs will
>>>>> have the same backend?
>>>>
>>>> Good question. I think, it is possible... This is technically what
>>>> V1 is
>>>> doing.
>>>>
>>>>
>>>> Are you asking because to support "iommus" for PCI devices as well to
>>>> describe that use-case with all PCI devices having the same
>>>> endpoint ID
>>>> (backend ID)?
>>>> If yes, I think, this could be still described by "iommu-map"
>>>> property,
>>>> something like that (if we don't want to describe mapping for each PCI
>>>> device one-by-one).
>>>>
>>>> iommu-map = <0x0 &iommu X 0x1>;
>>>>
>>>> iommu-map-mask = <0x0>;
>>>>
>>>> where the X is backend ID.
>>>>
>>>>
>>>> It feels to me that it should be written down somewhere that for
>>>> platform devices we expect "iommus" and for PCI devices we expect
>>>> "iommu-map/iommu-map-mask" to be present.
>>>
>>> Thanks for the clarification, now I got it. Yes I agree.
>>
>>
>> ok, good
>>
>>
>>>
>>>>>
>>>>>
>>>>>>>
>>>>>>>>
>>>>>>>>>          return false;
>>>>>>>>>      }
>>>>>>>>> @@ -325,12 +377,19 @@ bool xen_virtio_mem_acc(struct
>>>>>>>>> virtio_device
>>>>>>>>> *dev)
>>>>>>>>>      static int xen_dt_grant_init_backend_domid(struct device
>>>>>>>>> *dev,
>>>>>>>>>                             struct xen_grant_dma_data *data)
>>>>>>>>>      {
>>>>>>>>> -    struct of_phandle_args iommu_spec;
>>>>>>>>> +    struct of_phandle_args iommu_spec = { .args_count = 1 };
>>>>>>>>>      -    if (of_parse_phandle_with_args(dev->of_node, "iommus",
>>>>>>>>> "#iommu-cells",
>>>>>>>>> -            0, &iommu_spec)) {
>>>>>>>>> -        dev_err(dev, "Cannot parse iommus property\n");
>>>>>>>>> -        return -ESRCH;
>>>>>>>>> +    if (dev_is_pci(dev)) {
>>>>>>>>> +        if (xen_dt_map_id(dev, &iommu_spec.np,
>>>>>>>>> iommu_spec.args)) {
>>>>>>>>> +            dev_err(dev, "Cannot translate ID\n");
>>>>>>>>> +            return -ESRCH;
>>>>>>>>> +        }
>>>>>>>>> +    } else {
>>>>>>>>> +        if (of_parse_phandle_with_args(dev->of_node, "iommus",
>>>>>>>>> "#iommu-cells",
>>>>>>>>> +                0, &iommu_spec)) {
>>>>>>>>> +            dev_err(dev, "Cannot parse iommus property\n");
>>>>>>>>> +            return -ESRCH;
>>>>>>>>> +        }
>>>>>>>>>          }
>>>>>>>>>            if (!of_device_is_compatible(iommu_spec.np,
>>>>>>>>> "xen,grant-dma") ||
>>>>>>>>> @@ -354,6 +413,7 @@ static int
>>>>>>>>> xen_dt_grant_init_backend_domid(struct device *dev,
>>>>>>>>>      void xen_grant_setup_dma_ops(struct device *dev)
>>>>>>>>>      {
>>>>>>>>>          struct xen_grant_dma_data *data;
>>>>>>>>> +    struct device_node *np;
>>>>>>>>>            data = find_xen_grant_dma_data(dev);
>>>>>>>>>          if (data) {
>>>>>>>>> @@ -365,8 +425,13 @@ void xen_grant_setup_dma_ops(struct device
>>>>>>>>> *dev)
>>>>>>>>>          if (!data)
>>>>>>>>>              goto err;
>>>>>>>>>      -    if (dev->of_node) {
>>>>>>>>> -        if (xen_dt_grant_init_backend_domid(dev, data))
>>>>>>>>> +    np = xen_dt_get_node(dev);
>>>>>>>>> +    if (np) {
>>>>>>>>> +        int ret;
>>>>>>>>> +
>>>>>>>>> +        ret = xen_dt_grant_init_backend_domid(dev, data);
>>>>>>>>> +        of_node_put(np);
>>>>>>>>> +        if (ret)
>>>>>>>>>                  goto err;
>>>>>>>>>          } else if (IS_ENABLED(CONFIG_XEN_VIRTIO_FORCE_GRANT)) {
>>>>>>>>>              dev_info(dev, "Using dom0 as backend\n");
>>>>>>>>> --
>>>>>>>>> 2.25.1
>>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>
>>>
>
--
Regards,

Oleksandr Tyshchenko