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KVM: async_pf: Let guest support delivery of async_pf from guest mode

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Adds another flag bit (bit 2) to MSR_KVM_ASYNC_PF_EN. If bit 2 is 1,
async page faults are delivered to L1 as #PF vmexits; if bit 2 is 0,
kvm_can_do_async_pf returns 0 if in guest mode.

This is similar to what svm.c wanted to do all along, but it is only
enabled for Linux as L1 hypervisor.  Foreign hypervisors must never
receive async page faults as vmexits, because they'd probably be very
confused about that.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
This commit is contained in:
Wanpeng Li 2017-07-13 18:30:42 -07:00 committed by Radim Krčmář
parent adfe20fb48
commit 52a5c155cf
7 changed files with 16 additions and 7 deletions
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5
Documentation/virtual/kvm/msr.txt
View File

@ -166,10 +166,11 @@ MSR_KVM_SYSTEM_TIME: 0x12
MSR_KVM_ASYNC_PF_EN: 0x4b564d02
data: Bits 63-6 hold 64-byte aligned physical address of a
64 byte memory area which must be in guest RAM and must be
zeroed. Bits 5-2 are reserved and should be zero. Bit 0 is 1
zeroed. Bits 5-3 are reserved and should be zero. Bit 0 is 1
when asynchronous page faults are enabled on the vcpu 0 when
disabled. Bit 1 is 1 if asynchronous page faults can be injected
when vcpu is in cpl == 0.
when vcpu is in cpl == 0. Bit 2 is 1 if asynchronous page faults
are delivered to L1 as #PF vmexits.
First 4 byte of 64 byte memory location will be written to by
the hypervisor at the time of asynchronous page fault (APF)

1
arch/x86/include/asm/kvm_host.h
View File

@ -653,6 +653,7 @@ struct kvm_vcpu_arch {
bool send_user_only;
u32 host_apf_reason;
unsigned long nested_apf_token;
bool delivery_as_pf_vmexit;
} apf;
/* OSVW MSRs (AMD only) */

1
arch/x86/include/uapi/asm/kvm_para.h
View File

@ -67,6 +67,7 @@ struct kvm_clock_pairing {
#define KVM_ASYNC_PF_ENABLED (1 << 0)
#define KVM_ASYNC_PF_SEND_ALWAYS (1 << 1)
#define KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT (1 << 2)
/* Operations for KVM_HC_MMU_OP */
#define KVM_MMU_OP_WRITE_PTE 1

7
arch/x86/kernel/kvm.c
View File

@ -330,7 +330,12 @@ static void kvm_guest_cpu_init(void)
#ifdef CONFIG_PREEMPT
pa |= KVM_ASYNC_PF_SEND_ALWAYS;
#endif
wrmsrl(MSR_KVM_ASYNC_PF_EN, pa | KVM_ASYNC_PF_ENABLED);
pa |= KVM_ASYNC_PF_ENABLED;
/* Async page fault support for L1 hypervisor is optional */
if (wrmsr_safe(MSR_KVM_ASYNC_PF_EN,
(pa | KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT) & 0xffffffff, pa >> 32) < 0)
wrmsrl(MSR_KVM_ASYNC_PF_EN, pa);
__this_cpu_write(apf_reason.enabled, 1);
printk(KERN_INFO"KVM setup async PF for cpu %d\n",
smp_processor_id());

2
arch/x86/kvm/mmu.c
View File

@ -3749,7 +3749,7 @@ bool kvm_can_do_async_pf(struct kvm_vcpu *vcpu)
kvm_event_needs_reinjection(vcpu)))
return false;
if (is_guest_mode(vcpu))
if (!vcpu->arch.apf.delivery_as_pf_vmexit && is_guest_mode(vcpu))
return false;
return kvm_x86_ops->interrupt_allowed(vcpu);

2
arch/x86/kvm/vmx.c
View File

@ -8037,7 +8037,7 @@ static bool nested_vmx_exit_handled(struct kvm_vcpu *vcpu)
if (is_nmi(intr_info))
return false;
else if (is_page_fault(intr_info))
return enable_ept;
return !vmx->vcpu.arch.apf.host_apf_reason && enable_ept;
else if (is_no_device(intr_info) &&
!(vmcs12->guest_cr0 & X86_CR0_TS))
return false;

5
arch/x86/kvm/x86.c
View File

@ -2063,8 +2063,8 @@ static int kvm_pv_enable_async_pf(struct kvm_vcpu *vcpu, u64 data)
{
gpa_t gpa = data & ~0x3f;
/* Bits 2:5 are reserved, Should be zero */
if (data & 0x3c)
/* Bits 3:5 are reserved, Should be zero */
if (data & 0x38)
return 1;
vcpu->arch.apf.msr_val = data;
@ -2080,6 +2080,7 @@ static int kvm_pv_enable_async_pf(struct kvm_vcpu *vcpu, u64 data)
return 1;
vcpu->arch.apf.send_user_only = !(data & KVM_ASYNC_PF_SEND_ALWAYS);
vcpu->arch.apf.delivery_as_pf_vmexit = data & KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT;
kvm_async_pf_wakeup_all(vcpu);
return 0;
}