From: Sean Christopherson Date: Wed, 18 Oct 2023 19:36:17 +0000 (-0700) Subject: KVM: SVM: Explicitly require FLUSHBYASID to enable SEV support X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=770d6aa2e416fd26f0356e258c77a37574ad9b8c;p=linux.git KVM: SVM: Explicitly require FLUSHBYASID to enable SEV support Add a sanity check that FLUSHBYASID is available if SEV is supported in hardware, as SEV (and beyond) guests are bound to a single ASID, i.e. KVM can't "flush" by assigning a new, fresh ASID to the guest. If FLUSHBYASID isn't supported for some bizarre reason, KVM would completely fail to do TLB flushes for SEV+ guests (see pre_svm_run() and pre_sev_run()). Cc: Tom Lendacky Link: https://lore.kernel.org/r/20231018193617.1895752-1-seanjc@google.com Signed-off-by: Sean Christopherson --- diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index 4900c078045ac..d0c580607f009 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -2191,10 +2191,13 @@ void __init sev_hardware_setup(void) /* * SEV must obviously be supported in hardware. Sanity check that the * CPU supports decode assists, which is mandatory for SEV guests to - * support instruction emulation. + * support instruction emulation. Ditto for flushing by ASID, as SEV + * guests are bound to a single ASID, i.e. KVM can't rotate to a new + * ASID to effect a TLB flush. */ if (!boot_cpu_has(X86_FEATURE_SEV) || - WARN_ON_ONCE(!boot_cpu_has(X86_FEATURE_DECODEASSISTS))) + WARN_ON_ONCE(!boot_cpu_has(X86_FEATURE_DECODEASSISTS)) || + WARN_ON_ONCE(!boot_cpu_has(X86_FEATURE_FLUSHBYASID))) goto out; /* Retrieve SEV CPUID information */