linux-kernel - [PATCH] x86/sev: Do RMP memory coverage check after max

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Date: Wed, 5 Jun 2024 10:38:37 -0500
From: Tom Lendacky <thomas.lendacky@....com>
To: <linux-kernel@...r.kernel.org>, <x86@...nel.org>
CC: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
	Michael Roth <michael.roth@....com>, Ashish Kalra <ashish.kalra@....com>
Subject: [PATCH] x86/sev: Do RMP memory coverage check after max_pfn has been set

The RMP table is probed early in the boot process before max_pfn has been
set, so the logic to check if the RMP covers all of system memory is not
valid.

Move the RMP memory coverage check from snp_probe_rmptable_info() into
snp_rmptable_init(), which is well after max_pfn has been set.

Fixes: 216d106c7ff7 ("x86/sev: Add SEV-SNP host initialization support")
Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
---
 arch/x86/virt/svm/sev.c | 45 ++++++++++++++++++++---------------------
 1 file changed, 22 insertions(+), 23 deletions(-)

diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
index 0ae10535c699..0636fc5279e6 100644
--- a/arch/x86/virt/svm/sev.c
+++ b/arch/x86/virt/svm/sev.c
@@ -61,7 +61,7 @@ struct rmpentry {
 /* Mask to apply to a PFN to get the first PFN of a 2MB page */
 #define PFN_PMD_MASK	GENMASK_ULL(63, PMD_SHIFT - PAGE_SHIFT)
 
-static u64 probed_rmp_base, probed_rmp_size;
+static u64 probed_rmp_base, probed_rmp_end, probed_rmp_size;
 static struct rmpentry *rmptable __ro_after_init;
 static u64 rmptable_max_pfn __ro_after_init;
 
@@ -120,7 +120,7 @@ static __init void snp_enable(void *arg)
 
 bool snp_probe_rmptable_info(void)
 {
-	u64 max_rmp_pfn, calc_rmp_sz, rmp_sz, rmp_base, rmp_end;
+	u64 rmp_sz, rmp_base, rmp_end;
 
 	rdmsrl(MSR_AMD64_RMP_BASE, rmp_base);
 	rdmsrl(MSR_AMD64_RMP_END, rmp_end);
@@ -137,28 +137,12 @@ bool snp_probe_rmptable_info(void)
 
 	rmp_sz = rmp_end - rmp_base + 1;
 
-	/*
-	 * Calculate the amount the memory that must be reserved by the BIOS to
-	 * address the whole RAM, including the bookkeeping area. The RMP itself
-	 * must also be covered.
-	 */
-	max_rmp_pfn = max_pfn;
-	if (PHYS_PFN(rmp_end) > max_pfn)
-		max_rmp_pfn = PHYS_PFN(rmp_end);
-
-	calc_rmp_sz = (max_rmp_pfn << 4) + RMPTABLE_CPU_BOOKKEEPING_SZ;
-
-	if (calc_rmp_sz > rmp_sz) {
-		pr_err("Memory reserved for the RMP table does not cover full system RAM (expected 0x%llx got 0x%llx)\n",
-		       calc_rmp_sz, rmp_sz);
-		return false;
-	}
-
 	probed_rmp_base = rmp_base;
+	probed_rmp_end  = rmp_end;
 	probed_rmp_size = rmp_sz;
 
 	pr_info("RMP table physical range [0x%016llx - 0x%016llx]\n",
-		probed_rmp_base, probed_rmp_base + probed_rmp_size - 1);
+		probed_rmp_base, probed_rmp_end);
 
 	return true;
 }
@@ -206,9 +190,8 @@ void __init snp_fixup_e820_tables(void)
  */
 static int __init snp_rmptable_init(void)
 {
+	u64 max_rmp_pfn, calc_rmp_sz, rmptable_size, val;
 	void *rmptable_start;
-	u64 rmptable_size;
-	u64 val;
 
 	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
 		return 0;
@@ -219,10 +202,26 @@ static int __init snp_rmptable_init(void)
 	if (!probed_rmp_size)
 		goto nosnp;
 
+	/*
+	 * Calculate the amount the memory that must be reserved by the BIOS to
+	 * address the whole RAM, including the bookkeeping area. The RMP itself
+	 * must also be covered.
+	 */
+	max_rmp_pfn = max_pfn;
+	if (PHYS_PFN(probed_rmp_end) > max_pfn)
+		max_rmp_pfn = PHYS_PFN(probed_rmp_end);
+
+	calc_rmp_sz = (max_rmp_pfn << 4) + RMPTABLE_CPU_BOOKKEEPING_SZ;
+	if (calc_rmp_sz > probed_rmp_size) {
+		pr_err("Memory reserved for the RMP table does not cover full system RAM (expected 0x%llx got 0x%llx)\n",
+		       calc_rmp_sz, probed_rmp_size);
+		goto nosnp;
+	}
+
 	rmptable_start = memremap(probed_rmp_base, probed_rmp_size, MEMREMAP_WB);
 	if (!rmptable_start) {
 		pr_err("Failed to map RMP table\n");
-		return 1;
+		goto nosnp;
 	}
 
 	/*
-- 
2.43.2