| Message ID | 20170719112926.GA13502@potion (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Radim Krčmář <rkrcmar@redhat.com> wrote: > 2017-07-19 13:34+0800, Wanpeng Li: >> Ping, :) > > I misunderstood where the ball is ... is the patch below ok? > > ---8<--- > This can be reproduced by EPT=1, unrestricted_guest=N, emulate_invalid_state=Y > or EPT=0, the trace of kvm-unit-tests/taskswitch2.flat is like below, it > tries to emulate invalid guest state task-switch: > > kvm_exit: reason TASK_SWITCH rip 0x0 info 40000058 0 > kvm_emulate_insn: 42000:0:0f 0b (0x2) > kvm_emulate_insn: 42000:0:0f 0b (0x2) failed > kvm_inj_exception: #UD (0x0) > kvm_entry: vcpu 0 > kvm_exit: reason TASK_SWITCH rip 0x0 info 40000058 0 > kvm_emulate_insn: 42000:0:0f 0b (0x2) > kvm_emulate_insn: 42000:0:0f 0b (0x2) failed > kvm_inj_exception: #UD (0x0) > > It appears that the task-switch emulation updates rflags (and vm86 flag) > only after the segments are loaded, causing vmx->emulation_required to > be set, when in fact invalid guest state emulation is not needed. > > This patch fixes it by updating vmx->emulation_required after the rflags > (and vm86 flag) is updated. > > Suggested-by: Nadav Amit <nadav.amit@gmail.com> > Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com> > [Wanpeng wrote the commit message with initial patch and Radim moved the > update to vmx_set_rflags and added Paolo's suggestion for the check.] > Signed-off-by: Radim Krčmář <rkrcmar@redhat.com> > --- > arch/x86/kvm/vmx.c | 15 ++++++++++----- > 1 file changed, 10 insertions(+), 5 deletions(-) > > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > index 84e62acf2dd8..a776aea0043a 100644 > --- a/arch/x86/kvm/vmx.c > +++ b/arch/x86/kvm/vmx.c > @@ -2326,6 +2326,11 @@ static void vmx_vcpu_put(struct kvm_vcpu *vcpu) > __vmx_load_host_state(to_vmx(vcpu)); > } > > +static bool emulation_required(struct kvm_vcpu *vcpu) > +{ > + return emulate_invalid_guest_state && !guest_state_valid(vcpu); > +} > + > static void vmx_decache_cr0_guest_bits(struct kvm_vcpu *vcpu); > > /* > @@ -2363,6 +2368,8 @@ static unsigned long vmx_get_rflags(struct kvm_vcpu *vcpu) > > static void vmx_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags) > { > + unsigned long old_rflags = to_vmx(vcpu)->rflags; It assumes rflags was decached from the VMCS before. Probably it is true, but…
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 84e62acf2dd8..a776aea0043a 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -2326,6 +2326,11 @@ static void vmx_vcpu_put(struct kvm_vcpu *vcpu) __vmx_load_host_state(to_vmx(vcpu)); } +static bool emulation_required(struct kvm_vcpu *vcpu) +{ + return emulate_invalid_guest_state && !guest_state_valid(vcpu); +} + static void vmx_decache_cr0_guest_bits(struct kvm_vcpu *vcpu); /* @@ -2363,6 +2368,8 @@ static unsigned long vmx_get_rflags(struct kvm_vcpu *vcpu) static void vmx_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags) { + unsigned long old_rflags = to_vmx(vcpu)->rflags; + __set_bit(VCPU_EXREG_RFLAGS, (ulong *)&vcpu->arch.regs_avail); to_vmx(vcpu)->rflags = rflags; if (to_vmx(vcpu)->rmode.vm86_active) { @@ -2370,6 +2377,9 @@ static void vmx_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags) rflags |= X86_EFLAGS_IOPL | X86_EFLAGS_VM; } vmcs_writel(GUEST_RFLAGS, rflags); + + if ((old_rflags ^ rflags) & X86_EFLAGS_VM) + to_vmx(vcpu)->emulation_required = emulation_required(vcpu); } static u32 vmx_get_pkru(struct kvm_vcpu *vcpu) @@ -3857,11 +3867,6 @@ static __init int alloc_kvm_area(void) return 0; } -static bool emulation_required(struct kvm_vcpu *vcpu) -{ - return emulate_invalid_guest_state && !guest_state_valid(vcpu); -} - static void fix_pmode_seg(struct kvm_vcpu *vcpu, int seg, struct kvm_segment *save) {