check if there is a not-present cache present and flush it if there is.
Signed-off-by: Tom Murphy <[email protected]>
---
drivers/iommu/amd_iommu.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index f7cdd2ab7f11..8ef43224aae0 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -1636,6 +1636,12 @@ static int iommu_map_page(struct protection_domain *dom,
pte[i] = __pte;
update_domain(dom);
+ if (!dom->updated) {
+ if (unlikely(amd_iommu_np_cache)) {
+ domain_flush_pages(dom, bus_addr, page_size);
+ domain_flush_complete(dom);
+ }
+ }
/* Everything flushed out, free pages now */
free_page_list(freelist);
--
2.17.1
>The two conditions can go into one if statement to make this a little
>more clear.
Ah, yeah of course
>And I'd really like to understand the unlikely - amd_iommu_np_cache
>is set based on a hardware capability, so it seems rather odd to mark
>it unlikely. Dynamic branch prediction really should do the right thing
>here usually.
Here is the commit which added it without any explanation:
https://github.com/torvalds/linux/commit/270cab2426cdc6307725e4f1f46ecf8ab8e69193
should we remove it seen as there's no explanation given ?
On Wed, Apr 24, 2019 at 3:32 PM Christoph Hellwig <[email protected]> wrote:
>
> On Wed, Apr 24, 2019 at 03:18:59PM +0100, Tom Murphy via iommu wrote:
> > check if there is a not-present cache present and flush it if there is.
> >
> > Signed-off-by: Tom Murphy <[email protected]>
> > ---
> > drivers/iommu/amd_iommu.c | 6 ++++++
> > 1 file changed, 6 insertions(+)
> >
> > diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
> > index f7cdd2ab7f11..8ef43224aae0 100644
> > --- a/drivers/iommu/amd_iommu.c
> > +++ b/drivers/iommu/amd_iommu.c
> > @@ -1636,6 +1636,12 @@ static int iommu_map_page(struct protection_domain *dom,
> > pte[i] = __pte;
> >
> > update_domain(dom);
> > + if (!dom->updated) {
> > + if (unlikely(amd_iommu_np_cache)) {
> > + domain_flush_pages(dom, bus_addr, page_size);
> > + domain_flush_complete(dom);
> > + }
> > + }
>
> The two conditions can go into one if statement to make this a little
> more clear.
>
> And I'd really like to understand the unlikely - amd_iommu_np_cache
> is set based on a hardware capability, so it seems rather odd to mark
> it unlikely. Dynamic branch prediction really should do the right thing
> here usually.
On Wed, Apr 24, 2019 at 03:47:39PM +0100, Tom Murphy wrote:
> >And I'd really like to understand the unlikely - amd_iommu_np_cache
> >is set based on a hardware capability, so it seems rather odd to mark
> >it unlikely. Dynamic branch prediction really should do the right thing
> >here usually.
>
> Here is the commit which added it without any explanation:
> https://github.com/torvalds/linux/commit/270cab2426cdc6307725e4f1f46ecf8ab8e69193
>
> should we remove it seen as there's no explanation given ?
I'd be tempted to do that. But lets just ask Joerg if he has
any opinion..
On Wed, Apr 24, 2019 at 4:55 PM Joerg Roedel <[email protected]> wrote:
>
> On Wed, Apr 24, 2019 at 07:58:19AM -0700, Christoph Hellwig wrote:
> > I'd be tempted to do that. But lets just ask Joerg if he has
> > any opinion..
>
> The reason was that it is an unlikely path, as hardware implementations
> are not allowed to set this bit. It is purely for emulated AMD IOMMUs.
> I have not measured whether this annotation has any performance
> benefit, but I find it more readable at least.
In that case I will keep it in.
>
> Regards,
>
> Joerg
>
> PS: Why did you drop me from the Cc list of the previous replies?
On Wed, Apr 24, 2019 at 03:18:59PM +0100, Tom Murphy via iommu wrote:
> check if there is a not-present cache present and flush it if there is.
>
> Signed-off-by: Tom Murphy <[email protected]>
> ---
> drivers/iommu/amd_iommu.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
> index f7cdd2ab7f11..8ef43224aae0 100644
> --- a/drivers/iommu/amd_iommu.c
> +++ b/drivers/iommu/amd_iommu.c
> @@ -1636,6 +1636,12 @@ static int iommu_map_page(struct protection_domain *dom,
> pte[i] = __pte;
>
> update_domain(dom);
> + if (!dom->updated) {
> + if (unlikely(amd_iommu_np_cache)) {
> + domain_flush_pages(dom, bus_addr, page_size);
> + domain_flush_complete(dom);
> + }
> + }
The two conditions can go into one if statement to make this a little
more clear.
And I'd really like to understand the unlikely - amd_iommu_np_cache
is set based on a hardware capability, so it seems rather odd to mark
it unlikely. Dynamic branch prediction really should do the right thing
here usually.
On Wed, Apr 24, 2019 at 07:58:19AM -0700, Christoph Hellwig wrote:
> I'd be tempted to do that. But lets just ask Joerg if he has
> any opinion..
The reason was that it is an unlikely path, as hardware implementations
are not allowed to set this bit. It is purely for emulated AMD IOMMUs.
I have not measured whether this annotation has any performance
benefit, but I find it more readable at least.
Regards,
Joerg
PS: Why did you drop me from the Cc list of the previous replies?