x86/mtrr: Don't print errors if MtrrFixDramModEn is set when SNP enabled

SNP enabled platforms require the MtrrFixDramModeEn bit to be set across
all CPUs when SNP is enabled. Therefore, don't print error messages when
MtrrFixDramModeEn is set when bringing CPUs online.

Closes: https://lore.kernel.org/kvm/68b2d6bf-bce7-47f9-bebb-2652cc923ff9@linux.microsoft.com/
Reported-by: Jeremi Piotrowski <jpiotrowski@linux.microsoft.com>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240126041126.1927228-6-michael.roth@amd.com

diff --git a/arch/x86/kernel/cpu/mtrr/generic.c b/arch/x86/kernel/cpu/mtrr/generic.c
index d3524778a54517557a22064c0d3b7d1bf97b3394..422a4ddc2ab7c9408f1d2d21433fea7f320c6f85 100644 (file)
--- a/arch/x86/kernel/cpu/mtrr/generic.c
+++ b/arch/x86/kernel/cpu/mtrr/generic.c
@@ -108,6 +108,9 @@ static inline void k8_check_syscfg_dram_mod_en(void)
              (boot_cpu_data.x86 >= 0x0f)))
                return;
 
+       if (cpu_feature_enabled(X86_FEATURE_SEV_SNP))
+               return;
+
        rdmsr(MSR_AMD64_SYSCFG, lo, hi);
        if (lo & K8_MTRRFIXRANGE_DRAM_MODIFY) {
                pr_err(FW_WARN "MTRR: CPU %u: SYSCFG[MtrrFixDramModEn]"