[PATCH] iommu/vt-d: Restore IOMMU_CAP_CACHE_COHERENCY

[PATCH] iommu/vt-d: Restore IOMMU_CAP_CACHE_COHERENCY

[Alex Williamson]

In removing IOMMU_CAP_DEFERRED_FLUSH, the below referenced commit
was over-eager in removing the return, resulting in the test for
IOMMU_CAP_CACHE_COHERENCY falling through to an irrelevant option.

Restore dropped return.

Fixes: 1c18a1212c77 ("iommu/dma: Always allow DMA-FQ when iommupt provides the iommu_domain")
Signed-off-by: Alex Williamson <alex.williamson@nvidia.com>
---
 drivers/iommu/intel/iommu.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 63cee27d6a5c..c3d18cd77d2f 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -3212,6 +3212,7 @@ static bool intel_iommu_capable(struct device *dev, enum iommu_cap cap)
 
 	switch (cap) {
 	case IOMMU_CAP_CACHE_COHERENCY:
+		return true;
 	case IOMMU_CAP_PRE_BOOT_PROTECTION:
 		return dmar_platform_optin();
 	case IOMMU_CAP_ENFORCE_CACHE_COHERENCY:
-- 
2.51.0

Re: [PATCH] iommu/vt-d: Restore IOMMU_CAP_CACHE_COHERENCY

[Jason Gunthorpe]

On Wed, Apr 08, 2026 at 12:44:42PM -0600, Alex Williamson wrote:
> In removing IOMMU_CAP_DEFERRED_FLUSH, the below referenced commit
> was over-eager in removing the return, resulting in the test for
> IOMMU_CAP_CACHE_COHERENCY falling through to an irrelevant option.
> 
> Restore dropped return.
> 
> Fixes: 1c18a1212c77 ("iommu/dma: Always allow DMA-FQ when iommupt provides the iommu_domain")
> Signed-off-by: Alex Williamson <alex.williamson@nvidia.com>

I didn't think this was merged - I didn't get an email about it? Joerg
I've noticed alot of silent merges from you lately is that deliberate
or is something wrong?

But yes this is right:

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>

Kevin and I both missed it!!

Thanks,
Jason

RE: [PATCH] iommu/vt-d: Restore IOMMU_CAP_CACHE_COHERENCY

[Tian, Kevin]

> From: Jason Gunthorpe <jgg@nvidia.com>
> Sent: Thursday, April 9, 2026 7:50 AM
> 
> On Wed, Apr 08, 2026 at 12:44:42PM -0600, Alex Williamson wrote:
> > In removing IOMMU_CAP_DEFERRED_FLUSH, the below referenced commit
> > was over-eager in removing the return, resulting in the test for
> > IOMMU_CAP_CACHE_COHERENCY falling through to an irrelevant option.
> >
> > Restore dropped return.
> >
> > Fixes: 1c18a1212c77 ("iommu/dma: Always allow DMA-FQ when iommupt
> provides the iommu_domain")
> > Signed-off-by: Alex Williamson <alex.williamson@nvidia.com>
> 
> I didn't think this was merged - I didn't get an email about it? Joerg
> I've noticed alot of silent merges from you lately is that deliberate
> or is something wrong?
> 
> But yes this is right:
> 
> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
> 
> Kevin and I both missed it!!
> 

yes it's missed.

Reviewed-by: Kevin Tian <kevin.tian@intel.com>

Re: [PATCH] iommu/vt-d: Restore IOMMU_CAP_CACHE_COHERENCY

[Baolu Lu]

On 4/9/26 02:44, Alex Williamson wrote:
> In removing IOMMU_CAP_DEFERRED_FLUSH, the below referenced commit
> was over-eager in removing the return, resulting in the test for
> IOMMU_CAP_CACHE_COHERENCY falling through to an irrelevant option.
> 
> Restore dropped return.
> 
> Fixes: 1c18a1212c77 ("iommu/dma: Always allow DMA-FQ when iommupt provides the iommu_domain")
> Signed-off-by: Alex Williamson<alex.williamson@nvidia.com>
> ---
>   drivers/iommu/intel/iommu.c | 1 +
>   1 file changed, 1 insertion(+)

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>

Re: [PATCH] iommu/vt-d: Restore IOMMU_CAP_CACHE_COHERENCY

[Will Deacon]

On Wed, 08 Apr 2026 12:44:42 -0600, Alex Williamson wrote:
> In removing IOMMU_CAP_DEFERRED_FLUSH, the below referenced commit
> was over-eager in removing the return, resulting in the test for
> IOMMU_CAP_CACHE_COHERENCY falling through to an irrelevant option.
> 
> Restore dropped return.
> 
> 
> [...]

Applied to iommu (core), thanks!

[1/1] iommu/vt-d: Restore IOMMU_CAP_CACHE_COHERENCY
      https://git.kernel.org/iommu/c/ebfaf2bcc190

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev