Re: [PATCH AUTOSEL 5.10 2/6] x86/cpu: Don't clear X86_FEATURE_LAHF_LM flag in init_amd_k8() on AMD when running in a virtual machine

Hi!

From: Max Grobecker max@grobecker.info

[ Upstream commit a4248ee16f411ac1ea7dfab228a6659b111e3d65 ]

This can prevent some docker containers from starting or build scripts to create unoptimized binaries.

Admittably, this is more a small inconvenience than a severe bug in the kernel and the shoddy scripts that rely on parsing /proc/cpuinfo should be fixed instead.

I'd say this is not good stable candidate.

Best regards, Pavel

+++ b/arch/x86/kernel/cpu/amd.c @@ -839,7 +839,7 @@ static void init_amd_k8(struct cpuinfo_x86 *c) * (model = 0x14) and later actually support it. * (AMD Erratum #110, docId: 25759). */

• if (c->x86_model < 0x14 && cpu_has(c, X86_FEATURE_LAHF_LM)) {

• if (c->x86_model < 0x14 && cpu_has(c, X86_FEATURE_LAHF_LM) && !cpu_has(c, X86_FEATURE_HYPERVISOR)) { clear_cpu_cap(c, X86_FEATURE_LAHF_LM); if (!rdmsrl_amd_safe(0xc001100d, &value)) { value &= ~BIT_64(32);