FAILED: patch "[PATCH] iommu/amd: Don't split flush for amd_iommu_domain_flush_all()" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 69fe699afe1afcb730164b86c228483c2da05f94
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026071648-ogle-phonics-2909@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 69fe699afe1afcb730164b86c228483c2da05f94 Mon Sep 17 00:00:00 2001
From: Weinan Liu <[email protected]>
Date: Thu, 28 May 2026 22:31:47 +0000
Subject: [PATCH] iommu/amd: Don't split flush for amd_iommu_domain_flush_all()

We have observed multiple full invalidations occurring during device detach when we are done using the vfio-device.

blocked_domain_attach_device()
-> detach_device()

    -> amd_iommu_domain_flush_all()
      -> amd_iommu_domain_flush_pages(..., CMD_INV_IOMMU_ALL_PAGES_ADDRESS)

      	while (size != 0) {

          -> __domain_flush_pages( flush_size /* power of 2 flush_size */)
            -> domain_flush_pages_v1()
              -> build_inv_iommu_pages()
                -> build_inv_address()

         }

build_inv_address() will trigger a full invalidation if the chunk size > (1 << 51). Consequently, the guest will issue multiple full invalidations for a single call to amd_iommu_domain_flush_all()

Without this patch, we will see 10 time instead of 1 time full invalidations for every amd_iommu_domain_flush_all().

index f1333071da10..0c042668b32d 100644
@@ -1770,7 +1770,8 @@ void amd_iommu_domain_flush_pages(struct protection_domain *domain,
 {
 	lockdep_assert_held(&domain->lock);
 
-	if (likely(!amd_iommu_np_cache)) {
+	if (likely(!amd_iommu_np_cache) ||
+		size >= (1ULL<<52)) {
 		__domain_flush_pages(domain, address, size);
 
 		/* Wait until IOMMU TLB and all device IOTLB flushes are complete */

From: Weinan Liu <[email protected]>

[ Upstream commit 69fe699afe1afcb730164b86c228483c2da05f94 ]

We have observed multiple full invalidations occurring during device detach when we are done using the vfio-device.

blocked_domain_attach_device()
-> detach_device()

    -> amd_iommu_domain_flush_all()
      -> amd_iommu_domain_flush_pages(..., CMD_INV_IOMMU_ALL_PAGES_ADDRESS)

      	while (size != 0) {

          -> __domain_flush_pages( flush_size /* power of 2 flush_size */)
            -> domain_flush_pages_v1()
              -> build_inv_iommu_pages()
                -> build_inv_address()

         }

build_inv_address() will trigger a full invalidation if the chunk size > (1 << 51). Consequently, the guest will issue multiple full invalidations for a single call to amd_iommu_domain_flush_all()

Without this patch, we will see 10 time instead of 1 time full invalidations for every amd_iommu_domain_flush_all().

---
 drivers/iommu/amd/iommu.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

index d3a11be8d1ddd3..b4e4f21fe2bed3 100644
@@ -1284,7 +1284,8 @@ static void __domain_flush_pages(struct protection_domain *domain,
 static void domain_flush_pages(struct protection_domain *domain,
 			       u64 address, size_t size, int pde)
 {
-	if (likely(!amd_iommu_np_cache)) {
+	if (likely(!amd_iommu_np_cache) ||
+		size >= (1ULL<<52)) {
 		__domain_flush_pages(domain, address, size, pde);
 		return;
 	}

2.53.0