From: Nadav Amit <[email protected]>
On virtual machines, software must flush the IOTLB after each page table
entry update.
The iommu_map_sg() code iterates through the given scatter-gather list
and invokes iommu_map() for each element in the scatter-gather list,
which calls into the vendor IOMMU driver through iommu_ops callback. As
the result, a single sg mapping may lead to multiple IOTLB flushes.
Fix this by adding amd_iotlb_sync_map() callback and flushing at this
point after all sg mappings we set.
This commit is followed and inspired by commit 933fcd01e97e2
("iommu/vt-d: Add iotlb_sync_map callback").
Cc: Joerg Roedel <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Jiajun Cao <[email protected]>
Cc: Robin Murphy <[email protected]>
Cc: Lu Baolu <[email protected]>
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Nadav Amit <[email protected]>
---
drivers/iommu/amd/iommu.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index 128f2e889ced..dd23566f1db8 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -2027,6 +2027,16 @@ static int amd_iommu_attach_device(struct iommu_domain *dom,
return ret;
}
+static void amd_iommu_iotlb_sync_map(struct iommu_domain *dom,
+ unsigned long iova, size_t size)
+{
+ struct protection_domain *domain = to_pdomain(dom);
+ struct io_pgtable_ops *ops = &domain->iop.iop.ops;
+
+ if (ops->map)
+ domain_flush_np_cache(domain, iova, size);
+}
+
static int amd_iommu_map(struct iommu_domain *dom, unsigned long iova,
phys_addr_t paddr, size_t page_size, int iommu_prot,
gfp_t gfp)
@@ -2045,10 +2055,8 @@ static int amd_iommu_map(struct iommu_domain *dom, unsigned long iova,
if (iommu_prot & IOMMU_WRITE)
prot |= IOMMU_PROT_IW;
- if (ops->map) {
+ if (ops->map)
ret = ops->map(ops, iova, paddr, page_size, prot, gfp);
- domain_flush_np_cache(domain, iova, page_size);
- }
return ret;
}
@@ -2249,6 +2257,7 @@ const struct iommu_ops amd_iommu_ops = {
.attach_dev = amd_iommu_attach_device,
.detach_dev = amd_iommu_detach_device,
.map = amd_iommu_map,
+ .iotlb_sync_map = amd_iommu_iotlb_sync_map,
.unmap = amd_iommu_unmap,
.iova_to_phys = amd_iommu_iova_to_phys,
.probe_device = amd_iommu_probe_device,
--
2.25.1
On 2021-06-07 19:25, Nadav Amit wrote:
> From: Nadav Amit <[email protected]>
>
> On virtual machines, software must flush the IOTLB after each page table
> entry update.
>
> The iommu_map_sg() code iterates through the given scatter-gather list
> and invokes iommu_map() for each element in the scatter-gather list,
> which calls into the vendor IOMMU driver through iommu_ops callback. As
> the result, a single sg mapping may lead to multiple IOTLB flushes.
>
> Fix this by adding amd_iotlb_sync_map() callback and flushing at this
> point after all sg mappings we set.
>
> This commit is followed and inspired by commit 933fcd01e97e2
> ("iommu/vt-d: Add iotlb_sync_map callback").
>
> Cc: Joerg Roedel <[email protected]>
> Cc: Will Deacon <[email protected]>
> Cc: Jiajun Cao <[email protected]>
> Cc: Robin Murphy <[email protected]>
> Cc: Lu Baolu <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> Signed-off-by: Nadav Amit <[email protected]>
> ---
> drivers/iommu/amd/iommu.c | 15 ++++++++++++---
> 1 file changed, 12 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
> index 128f2e889ced..dd23566f1db8 100644
> --- a/drivers/iommu/amd/iommu.c
> +++ b/drivers/iommu/amd/iommu.c
> @@ -2027,6 +2027,16 @@ static int amd_iommu_attach_device(struct iommu_domain *dom,
> return ret;
> }
>
> +static void amd_iommu_iotlb_sync_map(struct iommu_domain *dom,
> + unsigned long iova, size_t size)
> +{
> + struct protection_domain *domain = to_pdomain(dom);
> + struct io_pgtable_ops *ops = &domain->iop.iop.ops;
> +
> + if (ops->map)
Not too critical since you're only moving existing code around, but is
ops->map ever not set? Either way the check ends up looking rather
out-of-place here :/
It's not very clear what the original intent was - I do wonder whether
it's supposed to be related to PAGE_MODE_NONE, but given that
amd_iommu_map() has an explicit check and errors out early in that case,
we'd never get here anyway. Possibly something to come back and clean up
later?
Robin.
> + domain_flush_np_cache(domain, iova, size);
> +}
> +
> static int amd_iommu_map(struct iommu_domain *dom, unsigned long iova,
> phys_addr_t paddr, size_t page_size, int iommu_prot,
> gfp_t gfp)
> @@ -2045,10 +2055,8 @@ static int amd_iommu_map(struct iommu_domain *dom, unsigned long iova,
> if (iommu_prot & IOMMU_WRITE)
> prot |= IOMMU_PROT_IW;
>
> - if (ops->map) {
> + if (ops->map)
> ret = ops->map(ops, iova, paddr, page_size, prot, gfp);
> - domain_flush_np_cache(domain, iova, page_size);
> - }
>
> return ret;
> }
> @@ -2249,6 +2257,7 @@ const struct iommu_ops amd_iommu_ops = {
> .attach_dev = amd_iommu_attach_device,
> .detach_dev = amd_iommu_detach_device,
> .map = amd_iommu_map,
> + .iotlb_sync_map = amd_iommu_iotlb_sync_map,
> .unmap = amd_iommu_unmap,
> .iova_to_phys = amd_iommu_iova_to_phys,
> .probe_device = amd_iommu_probe_device,
>
> On Jun 15, 2021, at 4:25 AM, Robin Murphy <[email protected]> wrote:
>
> On 2021-06-07 19:25, Nadav Amit wrote:
>> From: Nadav Amit <[email protected]>
>> On virtual machines, software must flush the IOTLB after each page table
>> entry update.
>> The iommu_map_sg() code iterates through the given scatter-gather list
>> and invokes iommu_map() for each element in the scatter-gather list,
>> which calls into the vendor IOMMU driver through iommu_ops callback. As
>> the result, a single sg mapping may lead to multiple IOTLB flushes.
>> Fix this by adding amd_iotlb_sync_map() callback and flushing at this
>> point after all sg mappings we set.
>> This commit is followed and inspired by commit 933fcd01e97e2
>> ("iommu/vt-d: Add iotlb_sync_map callback").
>> Cc: Joerg Roedel <[email protected]>
>> Cc: Will Deacon <[email protected]>
>> Cc: Jiajun Cao <[email protected]>
>> Cc: Robin Murphy <[email protected]>
>> Cc: Lu Baolu <[email protected]>
>> Cc: [email protected]
>> Cc: [email protected]
>> Signed-off-by: Nadav Amit <[email protected]>
>> ---
>> drivers/iommu/amd/iommu.c | 15 ++++++++++++---
>> 1 file changed, 12 insertions(+), 3 deletions(-)
>> diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
>> index 128f2e889ced..dd23566f1db8 100644
>> --- a/drivers/iommu/amd/iommu.c
>> +++ b/drivers/iommu/amd/iommu.c
>> @@ -2027,6 +2027,16 @@ static int amd_iommu_attach_device(struct iommu_domain *dom,
>> return ret;
>> }
>> +static void amd_iommu_iotlb_sync_map(struct iommu_domain *dom,
>> + unsigned long iova, size_t size)
>> +{
>> + struct protection_domain *domain = to_pdomain(dom);
>> + struct io_pgtable_ops *ops = &domain->iop.iop.ops;
>> +
>> + if (ops->map)
>
> Not too critical since you're only moving existing code around, but is ops->map ever not set? Either way the check ends up looking rather out-of-place here :/
>
> It's not very clear what the original intent was - I do wonder whether it's supposed to be related to PAGE_MODE_NONE, but given that amd_iommu_map() has an explicit check and errors out early in that case, we'd never get here anyway. Possibly something to come back and clean up later?
[ +Suravee ]
According to what I see in the git log, the checks for ops->map (as well as ops->unmap) were relatively recently introduced by Suravee [1] in preparation to AMD IOMMU v2 page tables [2]. Since I do not know what he plans, I prefer not to touch this code.
[1] https://lore.kernel.org/linux-iommu/[email protected]/
[2] https://lore.kernel.org/linux-iommu/[email protected]/