x86/sev: Do RMP memory coverage check after max_pfn has been set

JIRA: https://issues.redhat.com/browse/RHEL-49791

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. Also, fix
the calculation to use PFN_UP instead of PHYS_PFN, in order to compute
the required RMP size properly.

Fixes: 216d106 ("x86/sev: Add SEV-SNP host initialization support")
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/bec4364c7e34358cc576f01bb197a7796a109169.1718984524.git.thomas.lendacky@amd.com
(cherry picked from commit 0440feb)
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Author: bonzini

arch/x86/virt/svm/sev.c

@@ -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 +137,11 @@ 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_size = rmp_sz;
 
 	pr_info("RMP table physical range [0x%016llx - 0x%016llx]\n",
-		probed_rmp_base, probed_rmp_base + probed_rmp_size - 1);
+		rmp_base, rmp_end);
 
 	return true;
 }
@@ -206,9 +189,8 @@ void __init snp_fixup_e820_tables(void)
  */
 static int __init snp_rmptable_init(void)
 {
+	u64 max_rmp_pfn, calc_rmp_sz, rmptable_size, rmp_end, val;
 	void *rmptable_start;
-	u64 rmptable_size;
-	u64 val;
 
 	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
 		return 0;
@@ -219,10 +201,28 @@ static int __init snp_rmptable_init(void)
 	if (!probed_rmp_size)
 		goto nosnp;
 
+	rmp_end = probed_rmp_base + probed_rmp_size - 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 (PFN_UP(rmp_end) > max_pfn)
+		max_rmp_pfn = PFN_UP(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;
 	}
 
 	/*