[PATCH 4/4] KVM: async_pf: Let host know whether the guest support delivery async_pf as #PF vmexit

Wanpeng Li
2017-06-13T06:08:14Z

From: Wanpeng Li <wanpeng.li@hotmail.com>

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.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
---
Documentation/virtual/kvm/msr.txt | 5 +++--
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/include/uapi/asm/kvm_para.h | 1 +
arch/x86/kernel/kvm.c | 1 +
arch/x86/kvm/mmu.c | 2 +-
arch/x86/kvm/x86.c | 5 +++--
6 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/Documentation/virtual/kvm/msr.txt b/Documentation/virtual/kvm/msr.txt
index 0a9ea51..1ebecc1 100644
--- a/Documentation/virtual/kvm/msr.txt
+++ b/Documentation/virtual/kvm/msr.txt
@@ -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)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index d30576a..2766b2c 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -646,6 +646,7 @@ struct kvm_vcpu_arch {
u64 msr_val;
u32 id;
bool send_user_only;
+ bool delivery_as_pf_vmexit;
} apf;

/* OSVW MSRs (AMD only) */
diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h
index cff0bb6..a965e5b 100644
--- a/arch/x86/include/uapi/asm/kvm_para.h
+++ b/arch/x86/include/uapi/asm/kvm_para.h
@@ -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
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 43e10d6..1e29a77 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -330,6 +330,7 @@ static void kvm_guest_cpu_init(void)
#ifdef CONFIG_PREEMPT
pa |= KVM_ASYNC_PF_SEND_ALWAYS;
#endif
+ pa |= KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT;
wrmsrl(MSR_KVM_ASYNC_PF_EN, pa | KVM_ASYNC_PF_ENABLED);
__this_cpu_write(apf_reason.enabled, 1);
printk(KERN_INFO"KVM setup async PF for cpu %d\n",
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index cb82259..c49aecd 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -3704,7 +3704,7 @@ 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);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index d7f1a49..74cb944 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2061,8 +2061,8 @@ 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;
@@ -2078,6 +2078,7 @@ 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;
}
--
2.7.4