Upcoming Intel CPUs will support virtual x2APIC MSR writes to the vICR, i.e. will trap and generate an APIC-write VM-Exit instead of intercepting the WRMSR. Add support for handling "nodecode" x2APIC writes, which were previously impossible. Note, x2APIC MSR writes are 64 bits wide. Signed-off-by: Zeng Guang <guang.zeng@xxxxxxxxx> --- arch/x86/kvm/lapic.c | 25 ++++++++++++++++++++++--- 1 file changed, 22 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 629c116b0d3e..e4bcdab1fac0 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -67,6 +67,7 @@ static bool lapic_timer_advance_dynamic __read_mostly; #define LAPIC_TIMER_ADVANCE_NS_MAX 5000 /* 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 inline void __kvm_lapic_set_reg(char *regs, int reg_off, u32 val) { @@ -2227,10 +2228,28 @@ EXPORT_SYMBOL_GPL(kvm_lapic_set_eoi); /* emulate APIC access in a trap manner */ void kvm_apic_write_nodecode(struct kvm_vcpu *vcpu, u32 offset) { - u32 val = kvm_lapic_get_reg(vcpu->arch.apic, 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; - /* TODO: optimize to just emulate side effect w/o one more write */ - kvm_lapic_reg_write(vcpu->arch.apic, offset, val); + kvm_lapic_msr_read(apic, offset, &val); + if (val & APIC_ICR_BUSY) + kvm_x2apic_icr_write(apic, val); + else + kvm_apic_send_ipi(apic, (u32)val, (u32)(val >> 32)); + } 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); + } } EXPORT_SYMBOL_GPL(kvm_apic_write_nodecode); -- 2.27.0