Messages in this thread | | | From | Jim Mattson <> | Date | Fri, 2 Feb 2018 09:57:34 -0800 | Subject | Re: [PATCH v6 4/5] KVM: VMX: Allow direct access to MSR_IA32_SPEC_CTRL |
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On Thu, Feb 1, 2018 at 1:59 PM, KarimAllah Ahmed <karahmed@amazon.de> wrote: > [ Based on a patch from Ashok Raj <ashok.raj@intel.com> ] > > Add direct access to MSR_IA32_SPEC_CTRL for guests. This is needed for > guests that will only mitigate Spectre V2 through IBRS+IBPB and will not > be using a retpoline+IBPB based approach. > > To avoid the overhead of saving and restoring the MSR_IA32_SPEC_CTRL for > guests that do not actually use the MSR, only start saving and restoring > when a non-zero is written to it. > > No attempt is made to handle STIBP here, intentionally. Filtering STIBP > may be added in a future patch, which may require trapping all writes > if we don't want to pass it through directly to the guest. > > [dwmw2: Clean up CPUID bits, save/restore manually, handle reset] > > Cc: Asit Mallick <asit.k.mallick@intel.com> > Cc: Arjan Van De Ven <arjan.van.de.ven@intel.com> > Cc: Dave Hansen <dave.hansen@intel.com> > Cc: Andi Kleen <ak@linux.intel.com> > Cc: Andrea Arcangeli <aarcange@redhat.com> > Cc: Linus Torvalds <torvalds@linux-foundation.org> > Cc: Tim Chen <tim.c.chen@linux.intel.com> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Dan Williams <dan.j.williams@intel.com> > Cc: Jun Nakajima <jun.nakajima@intel.com> > Cc: Paolo Bonzini <pbonzini@redhat.com> > Cc: David Woodhouse <dwmw@amazon.co.uk> > Cc: Greg KH <gregkh@linuxfoundation.org> > Cc: Andy Lutomirski <luto@kernel.org> > Cc: Ashok Raj <ashok.raj@intel.com> > Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de> > Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Jim Mattson <jmattson@google.com>
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