iommu/amd: Globally detect SNP support

Modify existing SNP feature check to use the helper function
check_feature_on_all_iommus() to ensure consistency among all IOMMUs.
Also report IOMMU SNP support information for each IOMMU.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Link: https://lore.kernel.org/r/20220713225651.20758-6-suravee.suthikulpanit@amd.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

Author: ssuthiku-amd

drivers/iommu/amd/init.c

@@ -389,7 +389,7 @@ static void iommu_set_cwwb_range(struct amd_iommu *iommu)
 	u64 start = iommu_virt_to_phys((void *)iommu->cmd_sem);
 	u64 entry = start & PM_ADDR_MASK;
 
-	if (!iommu_feature(iommu, FEATURE_SNP))
+	if (!check_feature_on_all_iommus(FEATURE_SNP))
 		return;
 
 	/* Note:
@@ -804,7 +804,7 @@ static void *__init iommu_alloc_4k_pages(struct amd_iommu *iommu,
 	void *buf = (void *)__get_free_pages(gfp, order);
 
 	if (buf &&
-	    iommu_feature(iommu, FEATURE_SNP) &&
+	    check_feature_on_all_iommus(FEATURE_SNP) &&
 	    set_memory_4k((unsigned long)buf, (1 << order))) {
 		free_pages((unsigned long)buf, order);
 		buf = NULL;
@@ -2143,6 +2143,9 @@ static void print_iommu_info(void)
 			if (iommu->features & FEATURE_GAM_VAPIC)
 				pr_cont(" GA_vAPIC");
 
+			if (iommu->features & FEATURE_SNP)
+				pr_cont(" SNP");
+
 			pr_cont("\n");
 		}
 	}