[PATCH v3 3/8] x86/sev: Require the RMPREAD instruction after Fam19h

[Tom Lendacky <thomas.lendacky@amd.com>]

Limit usage of the non-architectural RMP format to Fam19h processors.
The RMPREAD instruction, with its architecture defined output, is
available, and should be used, for RMP access beyond Fam19h.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 arch/x86/kernel/cpu/amd.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 015971adadfc..ddbb6dd75fb2 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -358,7 +358,8 @@ static void bsp_determine_snp(struct cpuinfo_x86 *c)
 		 * for which the RMP table entry format is currently defined for.
 		 */
 		if (!cpu_has(c, X86_FEATURE_HYPERVISOR) &&
-		    c->x86 >= 0x19 && snp_probe_rmptable_info()) {
+		    (c->x86 == 0x19 || cpu_feature_enabled(X86_FEATURE_RMPREAD)) &&
+		    snp_probe_rmptable_info()) {
 			cc_platform_set(CC_ATTR_HOST_SEV_SNP);
 		} else {
 			setup_clear_cpu_cap(X86_FEATURE_SEV_SNP);
-- 
2.43.2