[PATCH] iommu/amd: Do not reallocate GA log buffers on resume

[Karl Mehltretter]

Commit c5e1a1eb9279 ("iommu/amd: Simplify and Consolidate Virtual APIC
(AVIC) Enablement") moved the GA log allocation from iommu_init_pci()
to enable_iommus_vapic(), which is called on every resume.

iommu_init_ga_log() assigns iommu->ga_log and iommu->ga_log_tail
unconditionally. Each resume therefore replaces the boot-time pointers
and leaks both old allocations. The function also uses GFP_KERNEL from a
syscore resume callback, where interrupts are disabled and the non-boot
CPUs are offline.

Return early if both buffers are already allocated. Clear the pointers
in free_ga_log() so a partial allocation failure cannot leave ga_log
dangling.

Fixes: c5e1a1eb9279 ("iommu/amd: Simplify and Consolidate Virtual APIC (AVIC) Enablement")
Assisted-by: Claude:claude-opus-5
Signed-off-by: Karl Mehltretter <kmehltretter@xxxxxxxxx>
---
Tested with custom QEMU with GA log emulation. Stock QEMU does not
advertise GAMSup and cannot reach this path. After five pm_test=core
cycles, nr_iommu_pages increased from 17 to 25 without the patch.

Testing on AVIC-capable hardware would be welcome.

 drivers/iommu/amd/init.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index 40726dfef2733..c6b106d5921e 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -909,7 +909,9 @@ static void free_ga_log(struct amd_iommu *iommu)
 {
 #ifdef CONFIG_IRQ_REMAP
 	iommu_free_pages(iommu->ga_log);
+	iommu->ga_log = NULL;
 	iommu_free_pages(iommu->ga_log_tail);
+	iommu->ga_log_tail = NULL;
 #endif
 }
 
@@ -956,6 +958,9 @@ static int iommu_init_ga_log(struct amd_iommu *iommu)
 	if (WARN_ON_ONCE(!AMD_IOMMU_GUEST_IR_VAPIC(amd_iommu_guest_ir)))
 		return -EINVAL;
 
+	if (iommu->ga_log && iommu->ga_log_tail)
+		return 0;
+
 	iommu->ga_log = iommu_alloc_pages_node_sz(nid, GFP_KERNEL, GA_LOG_SIZE);
 	if (!iommu->ga_log)
 		goto err_out;

base-commit: 4477a78374a57c3809b172ad30cceabda48c47c6
-- 
2.53.0