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.
Paolo
