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KVM: x86: Do not block APIC write for non ICR registers

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The commit 5413bcba7ed5 ("KVM: x86: Add support for vICR APIC-write
VM-Exits in x2APIC mode") introduces logic to prevent APIC write
for offset other than ICR in kvm_apic_write_nodecode() function.
This breaks x2AVIC support, which requires KVM to trap and emulate
x2APIC MSR writes.

Therefore, removes the warning and modify to logic to allow MSR write.

Fixes: 5413bcba7ed5 ("KVM: x86: Add support for vICR APIC-write VM-Exits in x2APIC mode")
Cc: Zeng Guang <guang.zeng@intel.com>
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Message-Id: <20220725053356.4275-1-suravee.suthikulpanit@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Suravee Suthikulpanit 2022-07-25 00:33:56 -05:00 committed by Paolo Bonzini
parent 0a8735a6ac
commit 1bd9dfec9f
1 changed files with 11 additions and 11 deletions
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22
arch/x86/kvm/lapic.c
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@ -69,6 +69,7 @@ static bool lapic_timer_advance_dynamic __read_mostly;
/* step-by-step approximation to mitigate fluctuation */
#define LAPIC_TIMER_ADVANCE_ADJUST_STEP 8
static int kvm_lapic_msr_read(struct kvm_lapic *apic, u32 reg, u64 *data);
static int kvm_lapic_msr_write(struct kvm_lapic *apic, u32 reg, u64 data);
static inline void __kvm_lapic_set_reg(char *regs, int reg_off, u32 val)
{
@ -2283,21 +2284,20 @@ void kvm_apic_write_nodecode(struct kvm_vcpu *vcpu, u32 offset)
struct kvm_lapic *apic = vcpu->arch.apic;
u64 val;
if (apic_x2apic_mode(apic)) {
/*
* When guest APIC is in x2APIC mode and IPI virtualization
* is enabled, accessing APIC_ICR may cause trap-like VM-exit
* on Intel hardware. Other offsets are not possible.
*/
if (WARN_ON_ONCE(offset != APIC_ICR))
return;
if (apic_x2apic_mode(apic))
kvm_lapic_msr_read(apic, offset, &val);
else
val = kvm_lapic_get_reg(apic, offset);
/*
* ICR is a single 64-bit register when x2APIC is enabled. For legacy
* xAPIC, ICR writes need to go down the common (slightly slower) path
* to get the upper half from ICR2.
*/
if (apic_x2apic_mode(apic) && offset == APIC_ICR) {
kvm_apic_send_ipi(apic, (u32)val, (u32)(val >> 32));
trace_kvm_apic_write(APIC_ICR, val);
} else {
val = kvm_lapic_get_reg(apic, offset);
/* TODO: optimize to just emulate side effect w/o one more write */
kvm_lapic_reg_write(apic, offset, (u32)val);
}