2017-10-11 2:55 GMT+08:00 Radim Krčmář <rkrcmar@xxxxxxxxxx>:
> 2017-10-09 15:51-0700, Wanpeng Li:
>> From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
>>
>> - XCR0 is reset to 1 by RESET but not INIT
>> - XSS is zeroed by both RESET and INIT
>> - BNDCFGU, BND0-BND3, BNDCFGS are zeroed by both RESET and INIT
>>
>> This patch does this according to SDM.
>>
>> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
>> Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx>
>> Cc: Jim Mattson <jmattson@xxxxxxxxxx>
>> Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
>> ---
>> v2 -> v3:
>> * fix null pointer deference
>> * fix patch description
>> v1 -> v2:
>> * XCR0 is not zeroed by INIT
>> * XSS, BNDCFGU, BND0-BND3, BNDCFGS are zeroed by both RESET and INIT
>>
>> arch/x86/kvm/vmx.c | 2 ++
>> arch/x86/kvm/x86.c | 15 +++++++++++++++
>> 2 files changed, 17 insertions(+)
>>
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> @@ -7804,18 +7804,33 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
>> kvm_async_pf_hash_reset(vcpu);
>> vcpu->arch.apf.halted = false;
>>
>> + if (kvm_mpx_supported()) {
>> + void *mpx_state_buffer;
>> +
>> + mpx_state_buffer = get_xsave_addr(&vcpu->arch.guest_fpu.state.xsave, XFEATURE_MASK_BNDREGS);
>> + if (mpx_state_buffer)
>> + memset(mpx_state_buffer, 0, sizeof(struct mpx_bndreg_state));
>
> I think we should call kvm_put_guest_fpu() before doing this.
> The register might be loaded in CPU and XSAVE instruction from
> vcpu_put() would overwrite any changes we did.
Except in vCPU creation path, vcpu_put() is called in the
destroy/error path, so I think it doesn't matter to overwrite changes
we did.
>
>> + mpx_state_buffer = get_xsave_addr(&vcpu->arch.guest_fpu.state.xsave, XFEATURE_MASK_BNDCSR);
>> + if (mpx_state_buffer)
>> + memset(mpx_state_buffer, 0, sizeof(u64));
>
> XFEATURE_MASK_BNDCSR is actually
>
> struct mpx_bndcsr {
> u64 bndcfgu;
> u64 bndstatus;
> } __packed;
>
> So clearing two u64 would be correct, thanks.
SDM section 9.1.1 just mentioned BNDCFGU will be cleared after
RESET/INIT, but not mentioned BNDSTATUS.
Regards,
Wanpeng Li
