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Subject[PATCH v7 11/12] Let host know whether the guest can handle async PF in non-userspace context.
Date
If guest can detect that it runs in non-preemptable context it can
handle async PFs at any time, so let host know that it can send async
PF even if guest cpu is not in userspace.

Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
---
Documentation/kvm/msr.txt | 6 +++---
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/include/asm/kvm_para.h | 1 +
arch/x86/kernel/kvm.c | 3 +++
arch/x86/kvm/x86.c | 5 +++--
5 files changed, 11 insertions(+), 5 deletions(-)
diff --git a/Documentation/kvm/msr.txt b/Documentation/kvm/msr.txt
index 27c11a6..d079aed 100644
--- a/Documentation/kvm/msr.txt
+++ b/Documentation/kvm/msr.txt
@@ -154,9 +154,10 @@ 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 5-1 are reserved and should be zero. Bit 0 is 1
+ zeroed. Bits 5-2 are reserved and should be zero. Bit 0 is 1
when asynchronous page faults are enabled on the vcpu 0 when
- disabled.
+ disabled. Bit 2 is 1 if asynchronous page faults can be injected
+ when vcpu is in cpl == 0.

First 4 byte of 64 byte memory location will be written to by
the hypervisor at the time of asynchronous page fault (APF)
@@ -184,4 +185,3 @@ MSR_KVM_ASYNC_PF_EN: 0x4b564d02

Currently type 2 APF will be always delivered on the same vcpu as
type 1 was, but guest should not rely on that.
-
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index f1868ed..d2fa951 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -422,6 +422,7 @@ struct kvm_vcpu_arch {
struct gfn_to_hva_cache data;
u64 msr_val;
u32 id;
+ bool send_user_only;
} apf;
};

diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
index fbfd367..d3a1a48 100644
--- a/arch/x86/include/asm/kvm_para.h
+++ b/arch/x86/include/asm/kvm_para.h
@@ -38,6 +38,7 @@
#define KVM_MAX_MMU_OP_BATCH 32

#define KVM_ASYNC_PF_ENABLED (1 << 0)
+#define KVM_ASYNC_PF_SEND_ALWAYS (1 << 1)

/* 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 47ea93e..91b3d65 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -449,6 +449,9 @@ void __cpuinit kvm_guest_cpu_init(void)
if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF) && kvmapf) {
u64 pa = __pa(&__get_cpu_var(apf_reason));

+#ifdef CONFIG_PREEMPT
+ pa |= KVM_ASYNC_PF_SEND_ALWAYS;
+#endif
wrmsrl(MSR_KVM_ASYNC_PF_EN, pa | KVM_ASYNC_PF_ENABLED);
__get_cpu_var(apf_reason).enabled = 1;
printk(KERN_INFO"KVM setup async PF for cpu %d\n",
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 8e2fc59..1e442df 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1435,8 +1435,8 @@ static int kvm_pv_enable_async_pf(struct kvm_vcpu *vcpu, u64 data)
{
gpa_t gpa = data & ~0x3f;

- /* Bits 1:5 are resrved, Should be zero */
- if (data & 0x3e)
+ /* Bits 2:5 are resrved, Should be zero */
+ if (data & 0x3c)
return 1;

vcpu->arch.apf.msr_val = data;
@@ -1450,6 +1450,7 @@ static int kvm_pv_enable_async_pf(struct kvm_vcpu *vcpu, u64 data)
if (kvm_gfn_to_hva_cache_init(vcpu->kvm, &vcpu->arch.apf.data, gpa))
return 1;

+ vcpu->arch.apf.send_user_only = !(data & KVM_ASYNC_PF_SEND_ALWAYS);
kvm_async_pf_wakeup_all(vcpu);
return 0;
}
--
1.7.1


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