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[PATCH v5 0/4] KVM: async_pf: Fix async pf exception injection

Started byWanpeng Li <kernellwp@gmail.com>
First post2017-06-27 03:50 +0200
Last post2017-06-28 00:50 +0200
Articles 7 — 2 participants

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  [PATCH v5 0/4] KVM: async_pf: Fix async pf exception injection Wanpeng Li <kernellwp@gmail.com> - 2017-06-27 03:50 +0200
    [PATCH v5 4/4] KVM: async_pf: Let host know whether the guest support delivery async_pf as #PF vmexit Wanpeng Li <kernellwp@gmail.com> - 2017-06-27 03:50 +0200
      Re: [PATCH v5 4/4] KVM: async_pf: Let host know whether the guest  support delivery async_pf as #PF vmexit Paolo Bonzini <pbonzini@redhat.com> - 2017-06-27 15:30 +0200
        Re: [PATCH v5 4/4] KVM: async_pf: Let host know whether the guest  support delivery async_pf as #PF vmexit Wanpeng Li <kernellwp@gmail.com> - 2017-06-28 00:50 +0200
    [PATCH v5 2/4] KVM: async_pf: Add L1 guest async_pf #PF vmexit handler Wanpeng Li <kernellwp@gmail.com> - 2017-06-27 03:50 +0200
      Re: [PATCH v5 2/4] KVM: async_pf: Add L1 guest async_pf #PF vmexit  handler Paolo Bonzini <pbonzini@redhat.com> - 2017-06-27 15:40 +0200
        Re: [PATCH v5 2/4] KVM: async_pf: Add L1 guest async_pf #PF vmexit handler Wanpeng Li <kernellwp@gmail.com> - 2017-06-28 00:50 +0200

#1675234 — [PATCH v5 0/4] KVM: async_pf: Fix async pf exception injection

FromWanpeng Li <kernellwp@gmail.com>
Date2017-06-27 03:50 +0200
Subject[PATCH v5 0/4] KVM: async_pf: Fix async pf exception injection
Message-ID<tWNND-1Pa-7@gated-at.bofh.it>
 INFO: task gnome-terminal-:1734 blocked for more than 120 seconds.
       Not tainted 4.12.0-rc4+ #8
 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
 gnome-terminal- D    0  1734   1015 0x00000000
 Call Trace:
  __schedule+0x3cd/0xb30
  schedule+0x40/0x90
  kvm_async_pf_task_wait+0x1cc/0x270
  ? __vfs_read+0x37/0x150
  ? prepare_to_swait+0x22/0x70
  do_async_page_fault+0x77/0xb0
  ? do_async_page_fault+0x77/0xb0
  async_page_fault+0x28/0x30

This is triggered by running both win7 and win2016 on L1 KVM simultaneously, 
and then gives stress to memory on L1, I can observed this hang on L1 when 
at least ~70% swap area is occupied on L0.

This is due to async pf was injected to L2 which should be injected to L1, 
L2 guest starts receiving pagefault w/ bogus %cr2(apf token from the host 
actually), and L1 guest starts accumulating tasks stuck in D state in 
kvm_async_pf_task_wait() since missing PAGE_READY async_pfs.

This patchset fixes it according to Radim's proposal "force a nested VM exit 
from nested_vmx_check_exception if the injected #PF is async_pf and handle 
the #PF VM exit in L1". https://www.spinics.net/lists/kvm/msg142498.html

Note: The patchset almost not touch SVM since I don't have AMD CPU to verify
the modification.

v4 -> v5:
 * utilize wrmsr_safe for MSR_KVM_ASYNC_PF_EN

v3 -> v4:
 * reuse pad field in kvm_vcpu_events for async_page_fault
 * update kvm_vcpu_events API documentations
 * change async_page_fault type in vcpu->arch.exception from bool to u8

v2 -> v3:
 * add the flag to the userspace interface(KVM_GET/PUT_VCPU_EVENTS)

v1 -> v2:
 * remove nested_vmx_check_exception nr parameter
 * construct a simple special vm-exit information field for async pf
 * introduce nested_apf_token to vcpu->arch.apf to avoid change the CR2 
   visible in L2 guest 
 * avoid pass the apf directed towards it (L1) into L2 if there is L3 
   at the moment

Wanpeng Li (4):
  KVM: x86: Simple kvm_x86_ops->queue_exception parameter
  KVM: async_pf: Add L1 guest async_pf #PF vmexit handler
  KVM: async_pf: Force a nested vmexit if the injected #PF is async_pf
  KVM: async_pf: Let host know whether the guest support delivery async_pf as #PF vmexit

 Documentation/virtual/kvm/api.txt     |  8 +++--
 Documentation/virtual/kvm/msr.txt     |  5 +--
 arch/x86/include/asm/kvm_emulate.h    |  1 +
 arch/x86/include/asm/kvm_host.h       |  7 ++--
 arch/x86/include/uapi/asm/kvm.h       |  3 +-
 arch/x86/include/uapi/asm/kvm_para.h  |  1 +
 arch/x86/kernel/kvm.c                 |  3 +-
 arch/x86/kvm/mmu.c                    |  2 +-
 arch/x86/kvm/svm.c                    |  8 +++--
 arch/x86/kvm/vmx.c                    | 61 +++++++++++++++++++++++++++--------
 arch/x86/kvm/x86.c                    | 28 ++++++++++------
 tools/arch/x86/include/uapi/asm/kvm.h |  3 +-
 12 files changed, 93 insertions(+), 37 deletions(-)

-- 
2.7.4

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#1675236 — [PATCH v5 4/4] KVM: async_pf: Let host know whether the guest support delivery async_pf as #PF vmexit

FromWanpeng Li <kernellwp@gmail.com>
Date2017-06-27 03:50 +0200
Subject[PATCH v5 4/4] KVM: async_pf: Let host know whether the guest support delivery async_pf as #PF vmexit
Message-ID<tWNND-1Pa-15@gated-at.bofh.it>
In reply to#1675234
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                | 3 ++-
 arch/x86/kvm/mmu.c                   | 2 +-
 arch/x86/kvm/vmx.c                   | 2 +-
 arch/x86/kvm/x86.c                   | 5 +++--
 7 files changed, 12 insertions(+), 7 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 2e84cc4..05d7de9 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -647,6 +647,7 @@ struct kvm_vcpu_arch {
 		u32 id;
 		bool send_user_only;
 		unsigned long nested_apf_token;
+		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..6d55441 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -330,7 +330,8 @@ 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_DELIVERY_AS_PF_VMEXIT | KVM_ASYNC_PF_ENABLED;
+		wrmsr_safe(MSR_KVM_ASYNC_PF_EN, pa & 0xffffffff, pa >> 32);
 		__this_cpu_write(apf_reason.enabled, 1);
 		printk(KERN_INFO"KVM setup async PF for cpu %d\n",
 		       smp_processor_id());
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/vmx.c b/arch/x86/kvm/vmx.c
index e7b9844..2e906cf 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -8025,7 +8025,7 @@ 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->apf_reason && enable_ept;
 		else if (is_no_device(intr_info) &&
 			 !(vmcs12->guest_cr0 & X86_CR0_TS))
 			return false;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9a2410c..fdaa429 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2064,8 +2064,8 @@ 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;
@@ -2081,6 +2081,7 @@ 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

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#1675697 — Re: [PATCH v5 4/4] KVM: async_pf: Let host know whether the guest support delivery async_pf as #PF vmexit

FromPaolo Bonzini <pbonzini@redhat.com>
Date2017-06-27 15:30 +0200
SubjectRe: [PATCH v5 4/4] KVM: async_pf: Let host know whether the guest support delivery async_pf as #PF vmexit
Message-ID<tWYJ4-14q-25@gated-at.bofh.it>
In reply to#1675236

On 27/06/2017 03:47, Wanpeng Li wrote:
> -		wrmsrl(MSR_KVM_ASYNC_PF_EN, pa | KVM_ASYNC_PF_ENABLED);
> +		pa |= KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT | KVM_ASYNC_PF_ENABLED;
> +		wrmsr_safe(MSR_KVM_ASYNC_PF_EN, pa & 0xffffffff, pa >> 32);
>  		__this_cpu_write(apf_reason.enabled, 1);

Better:

	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) < 0)
		wrmsrl(MSR_KVM_ASYNC_PF_EN, pa);

Thanks,

Paolo

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#1676234 — Re: [PATCH v5 4/4] KVM: async_pf: Let host know whether the guest support delivery async_pf as #PF vmexit

FromWanpeng Li <kernellwp@gmail.com>
Date2017-06-28 00:50 +0200
SubjectRe: [PATCH v5 4/4] KVM: async_pf: Let host know whether the guest support delivery async_pf as #PF vmexit
Message-ID<tX7t0-6Yu-25@gated-at.bofh.it>
In reply to#1675697
2017-06-27 21:19 GMT+08:00 Paolo Bonzini <pbonzini@redhat.com>:
>
>
> On 27/06/2017 03:47, Wanpeng Li wrote:
>> -             wrmsrl(MSR_KVM_ASYNC_PF_EN, pa | KVM_ASYNC_PF_ENABLED);
>> +             pa |= KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT | KVM_ASYNC_PF_ENABLED;
>> +             wrmsr_safe(MSR_KVM_ASYNC_PF_EN, pa & 0xffffffff, pa >> 32);
>>               __this_cpu_write(apf_reason.enabled, 1);
>
> Better:
>
>         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) < 0)
>                 wrmsrl(MSR_KVM_ASYNC_PF_EN, pa);

Good point. :)

Regards,
Wanpeng Li

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#1675237 — [PATCH v5 2/4] KVM: async_pf: Add L1 guest async_pf #PF vmexit handler

FromWanpeng Li <kernellwp@gmail.com>
Date2017-06-27 03:50 +0200
Subject[PATCH v5 2/4] KVM: async_pf: Add L1 guest async_pf #PF vmexit handler
Message-ID<tWNND-1Pa-11@gated-at.bofh.it>
In reply to#1675234
From: Wanpeng Li <wanpeng.li@hotmail.com>

This patch adds the L1 guest async page fault #PF vmexit handler, such
#PF is converted into vmexit from L2 to L1 on #PF which is then handled
by L1 similar to ordinary async page fault.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
---
 arch/x86/kvm/vmx.c | 34 ++++++++++++++++++++++++++++------
 1 file changed, 28 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index df825bb..f533cc1 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -616,6 +616,7 @@ struct vcpu_vmx {
 	bool emulation_required;
 
 	u32 exit_reason;
+	u32 apf_reason;
 
 	/* Posted interrupt descriptor */
 	struct pi_desc pi_desc;
@@ -5648,14 +5649,31 @@ static int handle_exception(struct kvm_vcpu *vcpu)
 	}
 
 	if (is_page_fault(intr_info)) {
-		/* EPT won't cause page fault directly */
-		BUG_ON(enable_ept);
 		cr2 = vmcs_readl(EXIT_QUALIFICATION);
-		trace_kvm_page_fault(cr2, error_code);
+		switch (vmx->apf_reason) {
+		default:
+			/* EPT won't cause page fault directly */
+			BUG_ON(enable_ept);
+			trace_kvm_page_fault(cr2, error_code);
 
-		if (kvm_event_needs_reinjection(vcpu))
-			kvm_mmu_unprotect_page_virt(vcpu, cr2);
-		return kvm_mmu_page_fault(vcpu, cr2, error_code, NULL, 0);
+			if (kvm_event_needs_reinjection(vcpu))
+				kvm_mmu_unprotect_page_virt(vcpu, cr2);
+			return kvm_mmu_page_fault(vcpu, cr2, error_code, NULL, 0);
+			break;
+		case KVM_PV_REASON_PAGE_NOT_PRESENT:
+			vmx->apf_reason = 0;
+			local_irq_disable();
+			kvm_async_pf_task_wait(cr2);
+			local_irq_enable();
+			break;
+		case KVM_PV_REASON_PAGE_READY:
+			vmx->apf_reason = 0;
+			local_irq_disable();
+			kvm_async_pf_task_wake(cr2);
+			local_irq_enable();
+			break;
+		}
+		return 0;
 	}
 
 	ex_no = intr_info & INTR_INFO_VECTOR_MASK;
@@ -8602,6 +8620,10 @@ static void vmx_complete_atomic_exit(struct vcpu_vmx *vmx)
 	vmx->exit_intr_info = vmcs_read32(VM_EXIT_INTR_INFO);
 	exit_intr_info = vmx->exit_intr_info;
 
+	/* if exit due to PF check for async PF */
+	if (is_page_fault(exit_intr_info))
+		vmx->apf_reason = kvm_read_and_reset_pf_reason();
+
 	/* Handle machine checks before interrupts are enabled */
 	if (is_machine_check(exit_intr_info))
 		kvm_machine_check();
-- 
2.7.4

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#1675707 — Re: [PATCH v5 2/4] KVM: async_pf: Add L1 guest async_pf #PF vmexit handler

FromPaolo Bonzini <pbonzini@redhat.com>
Date2017-06-27 15:40 +0200
SubjectRe: [PATCH v5 2/4] KVM: async_pf: Add L1 guest async_pf #PF vmexit handler
Message-ID<tWYSK-18m-27@gated-at.bofh.it>
In reply to#1675237

On 27/06/2017 03:46, Wanpeng Li wrote:
> From: Wanpeng Li <wanpeng.li@hotmail.com>
> 
> This patch adds the L1 guest async page fault #PF vmexit handler, such
> #PF is converted into vmexit from L2 to L1 on #PF which is then handled
> by L1 similar to ordinary async page fault.
> 
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Radim Krčmář <rkrcmar@redhat.com>
> Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
> ---
>  arch/x86/kvm/vmx.c | 34 ++++++++++++++++++++++++++++------
>  1 file changed, 28 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index df825bb..f533cc1 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -616,6 +616,7 @@ struct vcpu_vmx {
>  	bool emulation_required;
>  
>  	u32 exit_reason;
> +	u32 apf_reason;

Can you instead of move vcpu_svm's apf_reason field to kvm_vcpu_arch?
(e.g. vcpu->arch.apf.host_apf_reason)?

>  	/* Posted interrupt descriptor */
>  	struct pi_desc pi_desc;
> @@ -5648,14 +5649,31 @@ static int handle_exception(struct kvm_vcpu *vcpu)
>  	}
>  
>  	if (is_page_fault(intr_info)) {
> -		/* EPT won't cause page fault directly */
> -		BUG_ON(enable_ept);
>  		cr2 = vmcs_readl(EXIT_QUALIFICATION);
> -		trace_kvm_page_fault(cr2, error_code);
> +		switch (vmx->apf_reason) {
> +		default:
> +			/* EPT won't cause page fault directly */
> +			BUG_ON(enable_ept);
> +			trace_kvm_page_fault(cr2, error_code);
>  
> -		if (kvm_event_needs_reinjection(vcpu))
> -			kvm_mmu_unprotect_page_virt(vcpu, cr2);
> -		return kvm_mmu_page_fault(vcpu, cr2, error_code, NULL, 0);
> +			if (kvm_event_needs_reinjection(vcpu))
> +				kvm_mmu_unprotect_page_virt(vcpu, cr2);
> +			return kvm_mmu_page_fault(vcpu, cr2, error_code, NULL, 0);
> +			break;
> +		case KVM_PV_REASON_PAGE_NOT_PRESENT:
> +			vmx->apf_reason = 0;
> +			local_irq_disable();
> +			kvm_async_pf_task_wait(cr2);
> +			local_irq_enable();
> +			break;
> +		case KVM_PV_REASON_PAGE_READY:
> +			vmx->apf_reason = 0;
> +			local_irq_disable();
> +			kvm_async_pf_task_wake(cr2);
> +			local_irq_enable();
> +			break;
> +		}
> +		return 0;
>  	}


This code can be moved to a common function

	int kvm_handle_page_fault(struct kvm_vcpu *vcpu, u64 error_code,
				  u64 fault_address);

in mmu.c.  It can be used by vmx.c here and in svm.c's pf_interception.

You can change "enable_ept" to "tdp_enabled" (but please make that a
WARN_ON_ONCE, too).

Thanks,

Paolo

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#1676227 — Re: [PATCH v5 2/4] KVM: async_pf: Add L1 guest async_pf #PF vmexit handler

FromWanpeng Li <kernellwp@gmail.com>
Date2017-06-28 00:50 +0200
SubjectRe: [PATCH v5 2/4] KVM: async_pf: Add L1 guest async_pf #PF vmexit handler
Message-ID<tX7sZ-6Yu-7@gated-at.bofh.it>
In reply to#1675707
2017-06-27 21:30 GMT+08:00 Paolo Bonzini <pbonzini@redhat.com>:
>
>
> On 27/06/2017 03:46, Wanpeng Li wrote:
>> From: Wanpeng Li <wanpeng.li@hotmail.com>
>>
>> This patch adds the L1 guest async page fault #PF vmexit handler, such
>> #PF is converted into vmexit from L2 to L1 on #PF which is then handled
>> by L1 similar to ordinary async page fault.
>>
>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>> Cc: Radim Krčmář <rkrcmar@redhat.com>
>> Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
>> ---
>>  arch/x86/kvm/vmx.c | 34 ++++++++++++++++++++++++++++------
>>  1 file changed, 28 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>> index df825bb..f533cc1 100644
>> --- a/arch/x86/kvm/vmx.c
>> +++ b/arch/x86/kvm/vmx.c
>> @@ -616,6 +616,7 @@ struct vcpu_vmx {
>>       bool emulation_required;
>>
>>       u32 exit_reason;
>> +     u32 apf_reason;
>
> Can you instead of move vcpu_svm's apf_reason field to kvm_vcpu_arch?
> (e.g. vcpu->arch.apf.host_apf_reason)?

Agreed.

>
>>       /* Posted interrupt descriptor */
>>       struct pi_desc pi_desc;
>> @@ -5648,14 +5649,31 @@ static int handle_exception(struct kvm_vcpu *vcpu)
>>       }
>>
>>       if (is_page_fault(intr_info)) {
>> -             /* EPT won't cause page fault directly */
>> -             BUG_ON(enable_ept);
>>               cr2 = vmcs_readl(EXIT_QUALIFICATION);
>> -             trace_kvm_page_fault(cr2, error_code);
>> +             switch (vmx->apf_reason) {
>> +             default:
>> +                     /* EPT won't cause page fault directly */
>> +                     BUG_ON(enable_ept);
>> +                     trace_kvm_page_fault(cr2, error_code);
>>
>> -             if (kvm_event_needs_reinjection(vcpu))
>> -                     kvm_mmu_unprotect_page_virt(vcpu, cr2);
>> -             return kvm_mmu_page_fault(vcpu, cr2, error_code, NULL, 0);
>> +                     if (kvm_event_needs_reinjection(vcpu))
>> +                             kvm_mmu_unprotect_page_virt(vcpu, cr2);
>> +                     return kvm_mmu_page_fault(vcpu, cr2, error_code, NULL, 0);
>> +                     break;
>> +             case KVM_PV_REASON_PAGE_NOT_PRESENT:
>> +                     vmx->apf_reason = 0;
>> +                     local_irq_disable();
>> +                     kvm_async_pf_task_wait(cr2);
>> +                     local_irq_enable();
>> +                     break;
>> +             case KVM_PV_REASON_PAGE_READY:
>> +                     vmx->apf_reason = 0;
>> +                     local_irq_disable();
>> +                     kvm_async_pf_task_wake(cr2);
>> +                     local_irq_enable();
>> +                     break;
>> +             }
>> +             return 0;
>>       }
>
>
> This code can be moved to a common function
>
>         int kvm_handle_page_fault(struct kvm_vcpu *vcpu, u64 error_code,
>                                   u64 fault_address);
>
> in mmu.c.  It can be used by vmx.c here and in svm.c's pf_interception.
>
> You can change "enable_ept" to "tdp_enabled" (but please make that a
> WARN_ON_ONCE, too).

Agreed. :)

Regards,
Wanpeng Li

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