[PATCH 2/2] iommu/amd: Use maximum PPR log buffer size when SNP is enabled on Family 0x19

[Vasant Hegde <vasant.hegde@amd.com>]

Due to CVE-2023-20585, the PPR log buffer must use the maximum supported
size (512K) on Genoa (Family 0x19, model >= 0x10) systems when SNP is
enabled, to mitigate a potential security vulnerability. Note that Family
0x19 models below 0x10 (Milan) do not support PPR when SNP is enabled.
Hence the PPR log size increase is only applied for model >= 0x10.
All other systems continue to use the default PPR log buffer size (8K).

Apply the errata fix by making the following changes:

- Introduce global new variable (amd_iommu_pprlog_size) to have PPR log buffer
  size. Adjust variable size for Genoa family.

- Extend 'amd_iommu_apply_erratum_snp()' to also set the PPR log buffer
  size to maximum for Family 0x19 model >= 0x10 when SNP is enabled.

- Rename rename PPR_* macros to make it more readable.

Link: https://www.amd.com/en/resources/product-security/bulletin/amd-sb-3016.html
Cc: Borislav Petkov <bp@alien8.de>
Cc: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Cc: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
---
 drivers/iommu/amd/amd_iommu.h       |  1 +
 drivers/iommu/amd/amd_iommu_types.h | 11 ++++++-----
 drivers/iommu/amd/init.c            | 13 ++++++++++++-
 drivers/iommu/amd/ppr.c             |  8 +++++---
 4 files changed, 24 insertions(+), 9 deletions(-)

diff --git a/drivers/iommu/amd/amd_iommu.h b/drivers/iommu/amd/amd_iommu.h
index f1c486dcf0f3..834d8fabfba3 100644
--- a/drivers/iommu/amd/amd_iommu.h
+++ b/drivers/iommu/amd/amd_iommu.h
@@ -12,6 +12,7 @@
 #include "amd_iommu_types.h"
 
 extern int amd_iommu_evtlog_size;
+extern int amd_iommu_pprlog_size;
 
 irqreturn_t amd_iommu_int_thread(int irq, void *data);
 irqreturn_t amd_iommu_int_thread_evtlog(int irq, void *data);
diff --git a/drivers/iommu/amd/amd_iommu_types.h b/drivers/iommu/amd/amd_iommu_types.h
index c3430c09bc5c..f9f718087893 100644
--- a/drivers/iommu/amd/amd_iommu_types.h
+++ b/drivers/iommu/amd/amd_iommu_types.h
@@ -267,11 +267,12 @@
 #define EVTLOG_LEN_MASK_MAX	(0xFULL << EVTLOG_SIZE_SHIFT)
 
 /* Constants for PPR Log handling */
-#define PPR_LOG_ENTRIES		512
-#define PPR_LOG_SIZE_SHIFT	56
-#define PPR_LOG_SIZE_512	(0x9ULL << PPR_LOG_SIZE_SHIFT)
-#define PPR_ENTRY_SIZE		16
-#define PPR_LOG_SIZE		(PPR_ENTRY_SIZE * PPR_LOG_ENTRIES)
+#define PPRLOG_ENTRY_SIZE	0x10
+#define PPRLOG_SIZE_SHIFT	56
+#define PPRLOG_SIZE_DEF		SZ_8K	/* 512 entries */
+#define PPRLOG_LEN_MASK_DEF	(0x9ULL << PPRLOG_SIZE_SHIFT)
+#define PPRLOG_SIZE_MAX		SZ_512K	/* 32K entries */
+#define PPRLOG_LEN_MASK_MAX	(0xFULL << PPRLOG_SIZE_SHIFT)
 
 /* PAGE_SERVICE_REQUEST PPR Log Buffer Entry flags */
 #define PPR_FLAG_EXEC		0x002	/* Execute permission requested */
diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index 74effb847f48..a590f487937b 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -133,6 +133,7 @@ struct ivhd_entry {
 } __attribute__((packed));
 
 int amd_iommu_evtlog_size = EVTLOG_SIZE_DEF;
+int amd_iommu_pprlog_size = PPRLOG_SIZE_DEF;
 
 /*
  * An AMD IOMMU memory definition structure. It defines things like exclusion
@@ -3420,6 +3421,16 @@ static void amd_iommu_apply_erratum_snp(void)
 	amd_iommu_evtlog_size = EVTLOG_SIZE_MAX;
 	pr_info("Applying erratum: Increase Event log size to 0x%x\n",
 		amd_iommu_evtlog_size);
+
+	/*
+	 * Set PPR log buffer size to max.
+	 * (Family 0x19, model < 0x10 doesn't support PPR when SNP is enabled).
+	 */
+	if (boot_cpu_data.x86_model >= 0x10) {
+		amd_iommu_pprlog_size = PPRLOG_SIZE_MAX;
+		pr_info("Applying erratum: Increase PPR log size to 0x%x\n",
+			amd_iommu_pprlog_size);
+	}
 #endif
 }
 
@@ -4080,7 +4091,7 @@ int amd_iommu_snp_disable(void)
 		if (ret)
 			return ret;
 
-		ret = iommu_make_shared(iommu->ppr_log, PPR_LOG_SIZE);
+		ret = iommu_make_shared(iommu->ppr_log, amd_iommu_pprlog_size);
 		if (ret)
 			return ret;
 
diff --git a/drivers/iommu/amd/ppr.c b/drivers/iommu/amd/ppr.c
index e6767c057d01..1f8d2823bea4 100644
--- a/drivers/iommu/amd/ppr.c
+++ b/drivers/iommu/amd/ppr.c
@@ -20,7 +20,7 @@
 int __init amd_iommu_alloc_ppr_log(struct amd_iommu *iommu)
 {
 	iommu->ppr_log = iommu_alloc_4k_pages(iommu, GFP_KERNEL | __GFP_ZERO,
-					      PPR_LOG_SIZE);
+					      amd_iommu_pprlog_size);
 	return iommu->ppr_log ? 0 : -ENOMEM;
 }
 
@@ -33,7 +33,9 @@ void amd_iommu_enable_ppr_log(struct amd_iommu *iommu)
 
 	iommu_feature_enable(iommu, CONTROL_PPR_EN);
 
-	entry = iommu_virt_to_phys(iommu->ppr_log) | PPR_LOG_SIZE_512;
+	entry = iommu_virt_to_phys(iommu->ppr_log);
+	entry |= (amd_iommu_pprlog_size == PPRLOG_SIZE_DEF) ?
+			PPRLOG_LEN_MASK_DEF : PPRLOG_LEN_MASK_MAX;
 
 	memcpy_toio(iommu->mmio_base + MMIO_PPR_LOG_OFFSET,
 		    &entry, sizeof(entry));
@@ -201,7 +203,7 @@ void amd_iommu_poll_ppr_log(struct amd_iommu *iommu)
 			raw[0] = raw[1] = 0UL;
 
 		/* Update head pointer of hardware ring-buffer */
-		head = (head + PPR_ENTRY_SIZE) % PPR_LOG_SIZE;
+		head = (head + PPRLOG_ENTRY_SIZE) % amd_iommu_pprlog_size;
 		writel(head, iommu->mmio_base + MMIO_PPR_HEAD_OFFSET);
 
 		/* Handle PPR entry */
-- 
2.31.1