Il 17/12/2013 20:05, Jan Kiszka ha scritto:
> If the guest is running in nested mode on system reset, clearing the
> feature MSR signals the kernel to leave this mode. Recent kernels
> processes this properly, but leave the VCPU state undefined behind. It
> is the job of userspace to bring it to a proper shape. Therefore, write
> this specific MSR first so that no state transfer gets lost.
>
> This allows to cleanly reset a guest with VMX in use.
>
> Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
> ---
> target-i386/kvm.c | 32 ++++++++++++++++++++++++++++----
> 1 file changed, 28 insertions(+), 4 deletions(-)
>
> diff --git a/target-i386/kvm.c b/target-i386/kvm.c
> index 1188482..ec51447 100644
> --- a/target-i386/kvm.c
> +++ b/target-i386/kvm.c
> @@ -1104,6 +1104,25 @@ static int kvm_put_tscdeadline_msr(X86CPU *cpu)
> return kvm_vcpu_ioctl(CPU(cpu), KVM_SET_MSRS, &msr_data);
> }
>
> +/*
> + * Provide a separate write service for the feature control MSR in order to
> + * kick the VCPU out of VMXON or even guest mode on reset. This has to be done
> + * before writing any other state because forcibly leaving nested mode
> + * invalidates the VCPU state.
> + */
> +static int kvm_put_msr_feature_control(X86CPU *cpu)
> +{
> + struct {
> + struct kvm_msrs info;
> + struct kvm_msr_entry entry;
> + } msr_data;
> +
> + kvm_msr_entry_set(&msr_data.entry, MSR_IA32_FEATURE_CONTROL,
> + cpu->env.msr_ia32_feature_control);
> + msr_data.info.nmsrs = 1;
> + return kvm_vcpu_ioctl(CPU(cpu), KVM_SET_MSRS, &msr_data);
> +}
> +
> static int kvm_put_msrs(X86CPU *cpu, int level)
> {
> CPUX86State *env = &cpu->env;
> @@ -1204,10 +1223,8 @@ static int kvm_put_msrs(X86CPU *cpu, int level)
> if (cpu->hyperv_vapic) {
> kvm_msr_entry_set(&msrs[n++], HV_X64_MSR_APIC_ASSIST_PAGE, 0);
> }
> - if (has_msr_feature_control) {
> - kvm_msr_entry_set(&msrs[n++], MSR_IA32_FEATURE_CONTROL,
> - env->msr_ia32_feature_control);
> - }
> + /* Note: MSR_IA32_FEATURE_CONTROL is written separately, see
> + * kvm_put_msr_feature_control. */
> }
> if (env->mcg_cap) {
> int i;
> @@ -1801,6 +1818,13 @@ int kvm_arch_put_registers(CPUState *cpu, int level)
>
> assert(cpu_is_stopped(cpu) || qemu_cpu_is_self(cpu));
>
> + if (level >= KVM_PUT_RESET_STATE && has_msr_feature_control) {
> + ret = kvm_put_msr_feature_control(x86_cpu);
> + if (ret < 0) {
> + return ret;
> + }
> + }
> +
> ret = kvm_getput_regs(x86_cpu, 1);
> if (ret < 0) {
> return ret;
>
Applied, thanks!
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