[PATCH] iommu/vt-d: Don't read VCCAP register unless it exists

[David Woodhouse <dwmw2@infradead.org>]

[-- Attachment #1.1: Type: text/plain, Size: 2050 bytes --]

From: David Woodhouse <dwmw@amazon.co.uk>

My virtual IOMMU implementation is whining that the guest is reading a
register that doesn't exist. Only read the VCCAP_REG if the corresponding
capability is set in ECAP_REG to indicate that it actually exists.

Fixes: 3375303e8287 ("iommu/vt-d: Add custom allocator for IOASID")
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Liu Yi L <yi.l.liu@intel.com>
Cc: stable@vger.kernel.org # v5.7+
---
 drivers/iommu/intel/dmar.c  | 3 ++-
 drivers/iommu/intel/iommu.c | 4 ++--
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c
index 404b40af31cb..38d1d40cfe34 100644
--- a/drivers/iommu/intel/dmar.c
+++ b/drivers/iommu/intel/dmar.c
@@ -967,7 +967,8 @@ static int map_iommu(struct intel_iommu *iommu, u64 phys_addr)
 		warn_invalid_dmar(phys_addr, " returns all ones");
 		goto unmap;
 	}
-	iommu->vccap = dmar_readq(iommu->reg + DMAR_VCCAP_REG);
+	if (ecap_vcs(iommu->ecap))
+		iommu->vccap = dmar_readq(iommu->reg + DMAR_VCCAP_REG);
 
 	/* the registers might be more than one page */
 	map_size = max_t(int, ecap_max_iotlb_offset(iommu->ecap),
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 8651f6d4dfa0..0823761f3a7c 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -1833,7 +1833,7 @@ static void free_dmar_iommu(struct intel_iommu *iommu)
 		if (ecap_prs(iommu->ecap))
 			intel_svm_finish_prq(iommu);
 	}
-	if (ecap_vcs(iommu->ecap) && vccap_pasid(iommu->vccap))
+	if (vccap_pasid(iommu->vccap))
 		ioasid_unregister_allocator(&iommu->pasid_allocator);
 
 #endif
@@ -3209,7 +3209,7 @@ static void register_pasid_allocator(struct intel_iommu *iommu)
 	 * is active. All vIOMMU allocators will eventually be calling the same
 	 * host allocator.
 	 */
-	if (!ecap_vcs(iommu->ecap) || !vccap_pasid(iommu->vccap))
+	if (!vccap_pasid(iommu->vccap))
 		return;
 
 	pr_info("Register custom PASID allocator\n");



[-- Attachment #1.2: smime.p7s --]
[-- Type: application/x-pkcs7-signature, Size: 5174 bytes --]

[-- Attachment #2: Type: text/plain, Size: 156 bytes --]

_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu