2017-10-11 08:39+0800, Wanpeng Li: > 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. Yeah, creation doesn't have FPU loaded and destroy doesn't matter in any case, but we also have the INIT path from kvm_apic_accept_events() that can be called with loaded FPU and does not let userspace fix the state. > >> + 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. That section conspires ;) I found a mention in 17.3.3 Configuration and Status Registers: RESET or INIT# will set BNDCFGx and BNDSTATUS registers to zero.