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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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