2017-10-11 2:55 GMT+08:00 Radim Krčmář <rkrc...@redhat.com>: > 2017-10-09 15:51-0700, Wanpeng Li: >> From: Wanpeng Li <wanpeng...@hotmail.com> >> >> - 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 <pbonz...@redhat.com> >> Cc: Radim Krčmář <rkrc...@redhat.com> >> Cc: Jim Mattson <jmatt...@google.com> >> Signed-off-by: Wanpeng Li <wanpeng...@hotmail.com> >> --- >> 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