Re: [PATCH 33/44] KVM: x86: Do VMX/SVM support checks directly in vendor code
From: Sean Christopherson <seanjc@google.com>
Date: 2022-11-03 18:35:15
Also in:
kvm, kvm-riscv, kvmarm, linux-mips, linux-riscv, linux-s390, linuxppc-dev, lkml
On Thu, Nov 03, 2022, Paolo Bonzini wrote:
On 11/3/22 00:19, Sean Christopherson wrote:quoted
+ if (!boot_cpu_has(X86_FEATURE_MSR_IA32_FEAT_CTL) || + !boot_cpu_has(X86_FEATURE_VMX)) { + pr_err("VMX not enabled in MSR_IA32_FEAT_CTL\n"); + return false;I think the reference to the BIOS should remain in these messages and in svm.c (even though these days it's much less common for vendors to default to disabled virtualization in the system setup).
Ya, I'll figure out a way to mention BIOS/firmware.
The check for X86_FEATURE_MSR_IA32_FEAT_CTL is not needed because init_ia32_feat_ctl() will clear X86_FEATURE_VMX if the rdmsr fail (and not set X86_FEATURE_MSR_IA32_FEAT_CTL).
It's technically required. IA32_FEAT_CTL and thus KVM_INTEL depends on any of
CPU_SUP_{INTEL,CENATUR,ZHAOXIN}, but init_ia32_feat_ctl() is invoked if and only
if the actual CPU type matches one of the aforementioned CPU_SUP_*.
E.g. running a kernel built with
CONFIG_CPU_SUP_INTEL=y
CONFIG_CPU_SUP_AMD=y
# CONFIG_CPU_SUP_HYGON is not set
# CONFIG_CPU_SUP_CENTAUR is not set
# CONFIG_CPU_SUP_ZHAOXIN is not set
on a Cenatur or Zhaoxin CPU will leave X86_FEATURE_VMX set but not set
X86_FEATURE_MSR_IA32_FEAT_CTL. If VMX isn't enabled in MSR_IA32_FEAT_CTL, KVM
will get unexpected #UDs when trying to enable VMX.
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel