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    Subject[PATCH v5 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>
    ---
    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 +++--
    4 files changed, 8 insertions(+), 2 deletions(-)

    diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
    index 45e6c12..c675d5d 100644
    --- a/arch/x86/include/asm/kvm_host.h
    +++ b/arch/x86/include/asm/kvm_host.h
    @@ -367,6 +367,7 @@ struct kvm_vcpu_arch {
    cpumask_var_t wbinvd_dirty_mask;

    u32 __user *apf_data;
    + bool apf_send_user_only;
    u32 apf_memslot_ver;
    u64 apf_msr_val;
    u32 async_pf_id;
    diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
    index edf07cf..a33372c 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 914b0fc..462b47d 100644
    --- a/arch/x86/kernel/kvm.c
    +++ b/arch/x86/kernel/kvm.c
    @@ -429,6 +429,9 @@ void __cpuinit kvm_guest_cpu_init(void)
    if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF)) {
    u64 pa = __pa(&__get_cpu_var(apf_reason));

    +#ifdef CONFIG_PREEMPT
    + pa |= KVM_ASYNC_PF_SEND_ALWAYS;
    +#endif
    if (native_write_msr_safe(MSR_KVM_ASYNC_PF_EN,
    pa | KVM_ASYNC_PF_ENABLED, pa >> 32))
    return;
    diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    index 5482db0..ba351f5 100644
    --- a/arch/x86/kvm/x86.c
    +++ b/arch/x86/kvm/x86.c
    @@ -1222,8 +1222,8 @@ static int kvm_pv_enable_async_pf(struct kvm_vcpu *vcpu, u64 data)
    int offset = offset_in_page(gpa);
    unsigned long addr;

    - /* 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;
    @@ -1246,6 +1246,7 @@ static int kvm_pv_enable_async_pf(struct kvm_vcpu *vcpu, u64 data)
    return 1;
    }
    vcpu->arch.apf_memslot_ver = vcpu->kvm->memslot_version;
    + 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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