diff options
| author | Zhenzhong Duan | 2022-02-10 17:45:06 +0800 |
|---|---|---|
| committer | Paolo Bonzini | 2022-03-01 08:50:44 -0500 |
| commit | f66af9f222f08d5b11ea41c1bd6c07a0f12daa07 (patch) | |
| tree | 78789c0e2043b34a897632c1d0cef6a591274721 /arch/x86/kvm/lapic.c | |
| parent | b5f61c035d49a9724015ae5003109113d0914720 (diff) | |
KVM: x86: Fix emulation in writing cr8
In emulation of writing to cr8, one of the lowest four bits in TPR[3:0]
is kept.
According to Intel SDM 10.8.6.1(baremetal scenario):
"APIC.TPR[bits 7:4] = CR8[bits 3:0], APIC.TPR[bits 3:0] = 0";
and SDM 28.3(use TPR shadow):
"MOV to CR8. The instruction stores bits 3:0 of its source operand into
bits 7:4 of VTPR; the remainder of VTPR (bits 3:0 and bits 31:8) are
cleared.";
and AMD's APM 16.6.4:
"Task Priority Sub-class (TPS)-Bits 3 : 0. The TPS field indicates the
current sub-priority to be used when arbitrating lowest-priority messages.
This field is written with zero when TPR is written using the architectural
CR8 register.";
so in KVM emulated scenario, clear TPR[3:0] to make a consistent behavior
as in other scenarios.
This doesn't impact evaluation and delivery of pending virtual interrupts
because processor does not use the processor-priority sub-class to
determine which interrupts to delivery and which to inhibit.
Sub-class is used by hardware to arbitrate lowest priority interrupts,
but KVM just does a round-robin style delivery.
Fixes: b93463aa59d6 ("KVM: Accelerated apic support")
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220210094506.20181-1-zhenzhong.duan@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/lapic.c')
| -rw-r--r-- | arch/x86/kvm/lapic.c | 5 |
1 files changed, 1 insertions, 4 deletions
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 47f8606559a9..ad8857359ad6 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -2241,10 +2241,7 @@ void kvm_set_lapic_tscdeadline_msr(struct kvm_vcpu *vcpu, u64 data) void kvm_lapic_set_tpr(struct kvm_vcpu *vcpu, unsigned long cr8) { - struct kvm_lapic *apic = vcpu->arch.apic; - - apic_set_tpr(apic, ((cr8 & 0x0f) << 4) - | (kvm_lapic_get_reg(apic, APIC_TASKPRI) & 4)); + apic_set_tpr(vcpu->arch.apic, (cr8 & 0x0f) << 4); } u64 kvm_lapic_get_cr8(struct kvm_vcpu *vcpu) |