[PATCH v4 1/7] x86/sev: Create a function to clear/zero the RMP

[Tycho Andersen <tycho@kernel.org>]

From: Tom Lendacky <thomas.lendacky@amd.com>

In preparation for delayed SNP initialization and disablement on shutdown,
create a function, clear_rmp(), that clears the RMP bookkeeping area
and the RMP entries.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Tycho Andersen (AMD) <tycho@kernel.org>
---
 arch/x86/virt/svm/sev.c | 41 +++++++++++++++++++++++++++--------------
 1 file changed, 27 insertions(+), 14 deletions(-)

diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
index e35fac0a8a3d..025606969823 100644
--- a/arch/x86/virt/svm/sev.c
+++ b/arch/x86/virt/svm/sev.c
@@ -242,6 +242,32 @@ void __init snp_fixup_e820_tables(void)
 	}
 }
 
+static void clear_rmp(void)
+{
+	unsigned int i;
+	u64 val;
+
+	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
+		return;
+
+	/* Clearing the RMP while SNP is enabled will cause an exception */
+	rdmsrq(MSR_AMD64_SYSCFG, val);
+	if (WARN_ON_ONCE(val & MSR_AMD64_SYSCFG_SNP_EN))
+		return;
+
+	memset(rmp_bookkeeping, 0, RMPTABLE_CPU_BOOKKEEPING_SZ);
+
+	for (i = 0; i < rst_max_index; i++) {
+		struct rmp_segment_desc *desc;
+
+		desc = rmp_segment_table[i];
+		if (!desc)
+			continue;
+
+		memset(desc->rmp_entry, 0, desc->size);
+	}
+}
+
 static bool __init alloc_rmp_segment_desc(u64 segment_pa, u64 segment_size, u64 pa)
 {
 	u64 rst_index, rmp_segment_size_max;
@@ -484,7 +510,6 @@ static bool __init setup_rmptable(void)
  */
 int __init snp_rmptable_init(void)
 {
-	unsigned int i;
 	u64 val;
 
 	if (WARN_ON_ONCE(!cc_platform_has(CC_ATTR_HOST_SEV_SNP)))
@@ -504,19 +529,7 @@ int __init snp_rmptable_init(void)
 	if (val & MSR_AMD64_SYSCFG_SNP_EN)
 		goto skip_enable;
 
-	/* Zero out the RMP bookkeeping area */
-	memset(rmp_bookkeeping, 0, RMPTABLE_CPU_BOOKKEEPING_SZ);
-
-	/* Zero out the RMP entries */
-	for (i = 0; i < rst_max_index; i++) {
-		struct rmp_segment_desc *desc;
-
-		desc = rmp_segment_table[i];
-		if (!desc)
-			continue;
-
-		memset(desc->rmp_entry, 0, desc->size);
-	}
+	clear_rmp();
 
 	/* MtrrFixDramModEn must be enabled on all the CPUs prior to enabling SNP. */
 	on_each_cpu(mfd_enable, NULL, 1);
-- 
2.53.0