On Tue, Apr 14, 2020 at 10:28 AM Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
>
> On 11/04/20 17:36, Uros Bizjak wrote:
> > Use do_machine_check instead of INT $12 to pass MCE to the host,
> > the same approach VMX uses.
> >
> > On a related note, there is no reason to limit the use of do_machine_check
> > to 64 bit targets, as is currently done for VMX. MCE handling works
> > for both target families.
> >
> > The patch is only compile tested, for both, 64 and 32 bit targets,
> > someone should test the passing of the exception by injecting
> > some MCEs into the guest.
> >
> > For future non-RFC patch, kvm_machine_check should be moved to some
> > appropriate header file.
> >
> > Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> > Cc: Joerg Roedel <joro@xxxxxxxxxx>
> > Cc: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> > Signed-off-by: Uros Bizjak <ubizjak@xxxxxxxxx>
> > ---
> > arch/x86/kvm/svm/svm.c | 26 +++++++++++++++++++++-----
> > arch/x86/kvm/vmx/vmx.c | 2 +-
> > 2 files changed, 22 insertions(+), 6 deletions(-)
> >
> > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> > index 061d19e69c73..cd773f6261e3 100644
> > --- a/arch/x86/kvm/svm/svm.c
> > +++ b/arch/x86/kvm/svm/svm.c
> > @@ -33,6 +33,7 @@
> > #include <asm/debugreg.h>
> > #include <asm/kvm_para.h>
> > #include <asm/irq_remapping.h>
> > +#include <asm/mce.h>
> > #include <asm/spec-ctrl.h>
> > #include <asm/cpu_device_id.h>
> >
> > @@ -1839,6 +1840,25 @@ static bool is_erratum_383(void)
> > return true;
> > }
> >
> > +/*
> > + * Trigger machine check on the host. We assume all the MSRs are already set up
> > + * by the CPU and that we still run on the same CPU as the MCE occurred on.
> > + * We pass a fake environment to the machine check handler because we want
> > + * the guest to be always treated like user space, no matter what context
> > + * it used internally.
> > + */
> > +static void kvm_machine_check(void)
> > +{
> > +#if defined(CONFIG_X86_MCE)
> > + struct pt_regs regs = {
> > + .cs = 3, /* Fake ring 3 no matter what the guest ran on */
> > + .flags = X86_EFLAGS_IF,
> > + };
> > +
> > + do_machine_check(®s, 0);
> > +#endif
> > +}
> > +
> > static void svm_handle_mce(struct vcpu_svm *svm)
> > {
> > if (is_erratum_383()) {
> > @@ -1857,11 +1877,7 @@ static void svm_handle_mce(struct vcpu_svm *svm)
> > * On an #MC intercept the MCE handler is not called automatically in
> > * the host. So do it by hand here.
> > */
> > - asm volatile (
> > - "int $0x12\n");
> > - /* not sure if we ever come back to this point */
> > -
> > - return;
> > + kvm_machine_check();
> > }
> >
> > static int mc_interception(struct vcpu_svm *svm)
>
> Looks good, but please move kvm_machine_check() to x86.c instead.
Will do, after the confirmation that the patch works for AMD hosts.
OTOH, the function is just a simple wrapper around do_machine_check,
so I was thinking to move it to a kvm_host.h header as a static
inline. This way, we could save a call to a wrapper function.
Uros.
