* [PATCH RFC] KVM: async_pf: fix async_pf exception injection
@ 2017-06-08 9:30 Wanpeng Li
2017-06-08 11:52 ` Paolo Bonzini
0 siblings, 1 reply; 6+ messages in thread
From: Wanpeng Li @ 2017-06-08 9:30 UTC (permalink / raw)
To: linux-kernel, kvm; +Cc: Paolo Bonzini, Radim Krčmář, Wanpeng Li
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().
I try to fix 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
However, I found that "nr == PF_VECTOR && vmx->apf_reason != 0" never be true
in nested_vmx_check_exception(). SVM depends on the similar stuff in
nested_svm_intercept() which makes me confusing how it can works. In addition,
vmx/svm->apf_reason should be got in L1 since apf_reason.reason will make sense
just in pv guest. So vmx/svm->apf_reason should always be 0 on L0. I change the
condition to "nr == PF_VECTOR && error_code == 0" to intercept async_pf, however,
the below bug will be splatted:
BUG: unable to handle kernel paging request at ffffe305770a87e0
IP: kfree+0x6f/0x300
PGD 0
P4D 0
Oops: 0000 [#1] PREEMPT SMP
CPU: 3 PID: 2187 Comm: transhuge-stres Tainted: G OE 4.12.0-rc4+ #9
task: ffff8a9214b58000 task.stack: ffffb46bc34e4000
RIP: 0010:kfree+0x6f/0x300
RSP: 0000:ffffb46bc34e7b28 EFLAGS: 00010086
RAX: ffffe305770a87c0 RBX: ffffb46bc2a1fe70 RCX: 0000000000000001
RDX: 0000757180000000 RSI: 00000000ffffffff RDI: 0000000000000096
RBP: ffffb46bc34e7b50 R08: 0000000000000000 R09: 0000000000000001
R10: ffffb46bc34e7ac8 R11: 68b9962a00000000 R12: 000000a7770a87c0
R13: ffffffff90059b75 R14: ffffffff913466c0 R15: ffffe25e06f18000
FS: 00007f1904ae7700(0000) GS:ffff8a921a800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffe305770a87e0 CR3: 000000040eb5c000 CR4: 00000000001426e0
Call Trace:
kvm_async_pf_task_wait+0xd5/0x280
? __this_cpu_preempt_check+0x13/0x20
do_async_page_fault+0x77/0xb0
? do_async_page_fault+0x77/0xb0
async_page_fault+0x28/0x30
In additon, if svm->apf_reason doen't make sense on L0, then maybe it also will not
work in the function nested_svm_exit_special().
The patch below is uncompleted, and your inputs to improve it is a great appreciated.
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 | 41 ++++++++++++++++++++++++++++++++---------
1 file changed, 32 insertions(+), 9 deletions(-)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index ca5d2b9..21a1b44 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;
@@ -2418,11 +2419,12 @@ static void skip_emulated_instruction(struct kvm_vcpu *vcpu)
* KVM wants to inject page-faults which it got to the guest. This function
* checks whether in a nested guest, we need to inject them to L1 or L2.
*/
-static int nested_vmx_check_exception(struct kvm_vcpu *vcpu, unsigned nr)
+static int nested_vmx_check_exception(struct kvm_vcpu *vcpu, unsigned nr, u32 error_code)
{
struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
- if (!(vmcs12->exception_bitmap & (1u << nr)))
+ if (!((vmcs12->exception_bitmap & (1u << nr)) ||
+ (nr == PF_VECTOR && error_code == 0)))
return 0;
nested_vmx_vmexit(vcpu, EXIT_REASON_EXCEPTION_NMI,
@@ -2439,7 +2441,7 @@ static void vmx_queue_exception(struct kvm_vcpu *vcpu, unsigned nr,
u32 intr_info = nr | INTR_INFO_VALID_MASK;
if (!reinject && is_guest_mode(vcpu) &&
- nested_vmx_check_exception(vcpu, nr))
+ nested_vmx_check_exception(vcpu, nr, error_code))
return;
if (has_error_code) {
@@ -5646,14 +5648,31 @@ 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;
@@ -8600,6 +8619,10 @@ 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
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH RFC] KVM: async_pf: fix async_pf exception injection
2017-06-08 9:30 [PATCH RFC] KVM: async_pf: fix async_pf exception injection Wanpeng Li
@ 2017-06-08 11:52 ` Paolo Bonzini
2017-06-08 12:32 ` Wanpeng Li
2017-06-09 5:30 ` Wanpeng Li
0 siblings, 2 replies; 6+ messages in thread
From: Paolo Bonzini @ 2017-06-08 11:52 UTC (permalink / raw)
To: Wanpeng Li, linux-kernel, kvm; +Cc: Radim Krčmář, Wanpeng Li
On 08/06/2017 11:30, Wanpeng Li wrote:
> However, I found that "nr == PF_VECTOR && vmx->apf_reason != 0" never be true
> in nested_vmx_check_exception(). SVM depends on the similar stuff in
> nested_svm_intercept() which makes me confusing how it can works. In addition,
> vmx/svm->apf_reason should be got in L1 since apf_reason.reason will make sense
> just in pv guest. So vmx/svm->apf_reason should always be 0 on L0.
I agree. My suggestion is a series like this:
1) remove all arguments except the first in
kvm_x86_ops->queue_exception: they can extract the arguments from
vcpu->arch.exception themselves
2) do the same in nested_{vmx,svm}_check_exception
3) add an async_page_fault member to vcpu->arch.exception
> I change the
> condition to "nr == PF_VECTOR && error_code == 0" to intercept async_pf, however,
> the below bug will be splatted:
Right, because error_code == 0 is a valid error code.
For stable releases, this should be enough:
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index ac7810513d0e..c5f0023bac2d 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -3689,6 +3689,9 @@ static bool can_do_async_pf(struct kvm_vcpu *vcpu)
kvm_event_needs_reinjection(vcpu)))
return false;
+ if (is_guest_mode(vcpu))
+ return false;
+
return kvm_x86_ops->interrupt_allowed(vcpu);
}
For proper nested async page fault support, you have to be careful,
because old KVM as L1 you might crash due to the BUG(enable_ept); my
suggestion is to add another flag bit 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, can_do_async_pf returns 0 if in guest mode. When bit 2 is
1, async page fault exceptions override the usual exception/intercept
bitmaps, i.e. they always cause #PF vmexits. What do you think?
Thanks,
Paolo
> BUG: unable to handle kernel paging request at ffffe305770a87e0
> IP: kfree+0x6f/0x300
> PGD 0
> P4D 0
>
> Oops: 0000 [#1] PREEMPT SMP
> CPU: 3 PID: 2187 Comm: transhuge-stres Tainted: G OE 4.12.0-rc4+ #9
> task: ffff8a9214b58000 task.stack: ffffb46bc34e4000
> RIP: 0010:kfree+0x6f/0x300
> RSP: 0000:ffffb46bc34e7b28 EFLAGS: 00010086
> RAX: ffffe305770a87c0 RBX: ffffb46bc2a1fe70 RCX: 0000000000000001
> RDX: 0000757180000000 RSI: 00000000ffffffff RDI: 0000000000000096
> RBP: ffffb46bc34e7b50 R08: 0000000000000000 R09: 0000000000000001
> R10: ffffb46bc34e7ac8 R11: 68b9962a00000000 R12: 000000a7770a87c0
> R13: ffffffff90059b75 R14: ffffffff913466c0 R15: ffffe25e06f18000
> FS: 00007f1904ae7700(0000) GS:ffff8a921a800000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: ffffe305770a87e0 CR3: 000000040eb5c000 CR4: 00000000001426e0
> Call Trace:
> kvm_async_pf_task_wait+0xd5/0x280
> ? __this_cpu_preempt_check+0x13/0x20
> do_async_page_fault+0x77/0xb0
> ? do_async_page_fault+0x77/0xb0
> async_page_fault+0x28/0x30
>
> In additon, if svm->apf_reason doen't make sense on L0, then maybe it also will not
> work in the function nested_svm_exit_special().
>
> The patch below is uncompleted, and your inputs to improve it is a great appreciated.
The patch makes sense. Let's try to make more code common to VMX and
SVM too once the above is clarified.
Paolo
> 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 | 41 ++++++++++++++++++++++++++++++++---------
> 1 file changed, 32 insertions(+), 9 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index ca5d2b9..21a1b44 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;
> @@ -2418,11 +2419,12 @@ static void skip_emulated_instruction(struct kvm_vcpu *vcpu)
> * KVM wants to inject page-faults which it got to the guest. This function
> * checks whether in a nested guest, we need to inject them to L1 or L2.
> */
> -static int nested_vmx_check_exception(struct kvm_vcpu *vcpu, unsigned nr)
> +static int nested_vmx_check_exception(struct kvm_vcpu *vcpu, unsigned nr, u32 error_code)
> {
> struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
>
> - if (!(vmcs12->exception_bitmap & (1u << nr)))
> + if (!((vmcs12->exception_bitmap & (1u << nr)) ||
> + (nr == PF_VECTOR && error_code == 0)))
> return 0;
>
> nested_vmx_vmexit(vcpu, EXIT_REASON_EXCEPTION_NMI,
> @@ -2439,7 +2441,7 @@ static void vmx_queue_exception(struct kvm_vcpu *vcpu, unsigned nr,
> u32 intr_info = nr | INTR_INFO_VALID_MASK;
>
> if (!reinject && is_guest_mode(vcpu) &&
> - nested_vmx_check_exception(vcpu, nr))
> + nested_vmx_check_exception(vcpu, nr, error_code))
> return;
>
> if (has_error_code) {
> @@ -5646,14 +5648,31 @@ 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;
> @@ -8600,6 +8619,10 @@ 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();
>
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH RFC] KVM: async_pf: fix async_pf exception injection
2017-06-08 11:52 ` Paolo Bonzini
@ 2017-06-08 12:32 ` Wanpeng Li
2017-06-08 12:48 ` Paolo Bonzini
2017-06-09 5:30 ` Wanpeng Li
1 sibling, 1 reply; 6+ messages in thread
From: Wanpeng Li @ 2017-06-08 12:32 UTC (permalink / raw)
To: Paolo Bonzini; +Cc: linux-kernel, kvm, Radim Krčmář, Wanpeng Li
2017-06-08 19:52 GMT+08:00 Paolo Bonzini <pbonzini@redhat.com>:
>
>
> On 08/06/2017 11:30, Wanpeng Li wrote:
>> However, I found that "nr == PF_VECTOR && vmx->apf_reason != 0" never be true
>> in nested_vmx_check_exception(). SVM depends on the similar stuff in
>> nested_svm_intercept() which makes me confusing how it can works. In addition,
>> vmx/svm->apf_reason should be got in L1 since apf_reason.reason will make sense
>> just in pv guest. So vmx/svm->apf_reason should always be 0 on L0.
>
> I agree. My suggestion is a series like this:
>
> 1) remove all arguments except the first in
> kvm_x86_ops->queue_exception: they can extract the arguments from
> vcpu->arch.exception themselves
>
> 2) do the same in nested_{vmx,svm}_check_exception
>
> 3) add an async_page_fault member to vcpu->arch.exception
Agreed.
>
>> I change the
>> condition to "nr == PF_VECTOR && error_code == 0" to intercept async_pf, however,
>> the below bug will be splatted:
>
> Right, because error_code == 0 is a valid error code.
>
> For stable releases, this should be enough:
We should also take care PAGE_READY async_pfs injection. I will send a
patch to avoid async pf injection stuff in guest mode for stable
release.
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index ac7810513d0e..c5f0023bac2d 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -3689,6 +3689,9 @@ static bool can_do_async_pf(struct kvm_vcpu *vcpu)
> kvm_event_needs_reinjection(vcpu)))
> return false;
>
> + if (is_guest_mode(vcpu))
> + return false;
> +
> return kvm_x86_ops->interrupt_allowed(vcpu);
> }
>
>
> For proper nested async page fault support, you have to be careful,
> because old KVM as L1 you might crash due to the BUG(enable_ept); my
> suggestion is to add another flag bit 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, can_do_async_pf returns 0 if in guest mode. When bit 2 is
> 1, async page fault exceptions override the usual exception/intercept
> bitmaps, i.e. they always cause #PF vmexits. What do you think?
Agreed.
>
> Thanks,
>
> Paolo
>
>> BUG: unable to handle kernel paging request at ffffe305770a87e0
>> IP: kfree+0x6f/0x300
>> PGD 0
>> P4D 0
>>
>> Oops: 0000 [#1] PREEMPT SMP
>> CPU: 3 PID: 2187 Comm: transhuge-stres Tainted: G OE 4.12.0-rc4+ #9
>> task: ffff8a9214b58000 task.stack: ffffb46bc34e4000
>> RIP: 0010:kfree+0x6f/0x300
>> RSP: 0000:ffffb46bc34e7b28 EFLAGS: 00010086
>> RAX: ffffe305770a87c0 RBX: ffffb46bc2a1fe70 RCX: 0000000000000001
>> RDX: 0000757180000000 RSI: 00000000ffffffff RDI: 0000000000000096
>> RBP: ffffb46bc34e7b50 R08: 0000000000000000 R09: 0000000000000001
>> R10: ffffb46bc34e7ac8 R11: 68b9962a00000000 R12: 000000a7770a87c0
>> R13: ffffffff90059b75 R14: ffffffff913466c0 R15: ffffe25e06f18000
>> FS: 00007f1904ae7700(0000) GS:ffff8a921a800000(0000) knlGS:0000000000000000
>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> CR2: ffffe305770a87e0 CR3: 000000040eb5c000 CR4: 00000000001426e0
>> Call Trace:
>> kvm_async_pf_task_wait+0xd5/0x280
>> ? __this_cpu_preempt_check+0x13/0x20
>> do_async_page_fault+0x77/0xb0
>> ? do_async_page_fault+0x77/0xb0
>> async_page_fault+0x28/0x30
>>
>> In additon, if svm->apf_reason doen't make sense on L0, then maybe it also will not
>> work in the function nested_svm_exit_special().
>>
>> The patch below is uncompleted, and your inputs to improve it is a great appreciated.
>
> The patch makes sense. Let's try to make more code common to VMX and
> SVM too once the above is clarified.
Agreed.
Wanpeng Li
>
> Paolo
>
>> 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 | 41 ++++++++++++++++++++++++++++++++---------
>> 1 file changed, 32 insertions(+), 9 deletions(-)
>>
>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>> index ca5d2b9..21a1b44 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;
>> @@ -2418,11 +2419,12 @@ static void skip_emulated_instruction(struct kvm_vcpu *vcpu)
>> * KVM wants to inject page-faults which it got to the guest. This function
>> * checks whether in a nested guest, we need to inject them to L1 or L2.
>> */
>> -static int nested_vmx_check_exception(struct kvm_vcpu *vcpu, unsigned nr)
>> +static int nested_vmx_check_exception(struct kvm_vcpu *vcpu, unsigned nr, u32 error_code)
>> {
>> struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
>>
>> - if (!(vmcs12->exception_bitmap & (1u << nr)))
>> + if (!((vmcs12->exception_bitmap & (1u << nr)) ||
>> + (nr == PF_VECTOR && error_code == 0)))
>> return 0;
>>
>> nested_vmx_vmexit(vcpu, EXIT_REASON_EXCEPTION_NMI,
>> @@ -2439,7 +2441,7 @@ static void vmx_queue_exception(struct kvm_vcpu *vcpu, unsigned nr,
>> u32 intr_info = nr | INTR_INFO_VALID_MASK;
>>
>> if (!reinject && is_guest_mode(vcpu) &&
>> - nested_vmx_check_exception(vcpu, nr))
>> + nested_vmx_check_exception(vcpu, nr, error_code))
>> return;
>>
>> if (has_error_code) {
>> @@ -5646,14 +5648,31 @@ 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;
>> @@ -8600,6 +8619,10 @@ 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();
>>
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH RFC] KVM: async_pf: fix async_pf exception injection
2017-06-08 12:32 ` Wanpeng Li
@ 2017-06-08 12:48 ` Paolo Bonzini
0 siblings, 0 replies; 6+ messages in thread
From: Paolo Bonzini @ 2017-06-08 12:48 UTC (permalink / raw)
To: Wanpeng Li; +Cc: linux-kernel, kvm, Radim Krčmář, Wanpeng Li
On 08/06/2017 14:32, Wanpeng Li wrote:
>>> I change the
>>> condition to "nr == PF_VECTOR && error_code == 0" to intercept async_pf, however,
>>> the below bug will be splatted:
>> Right, because error_code == 0 is a valid error code.
>>
>> For stable releases, this should be enough:
>
> We should also take care PAGE_READY async_pfs injection. I will send a
> patch to avoid async pf injection stuff in guest mode for stable
> release.
Right, the simplest thing to do here is another is_guest_mode check in
kvm_arch_can_inject_async_page_present. That would delay the signaling
of ready pages while L2 runs, but hopefully we're under memory pressure
so L2 will get a page fault too.
In fact, kvm_arch_can_inject_async_page_present should just be
if (!(vcpu->arch.apf.msr_val & KVM_ASYNC_PF_ENABLED))
return true;
else
return can_do_async_pf(vcpu);
where can_do_async_pf becomes nonstatic.
Paolo
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH RFC] KVM: async_pf: fix async_pf exception injection
2017-06-08 11:52 ` Paolo Bonzini
2017-06-08 12:32 ` Wanpeng Li
@ 2017-06-09 5:30 ` Wanpeng Li
2017-06-09 11:32 ` Paolo Bonzini
1 sibling, 1 reply; 6+ messages in thread
From: Wanpeng Li @ 2017-06-09 5:30 UTC (permalink / raw)
To: Paolo Bonzini; +Cc: linux-kernel, kvm, Radim Krčmář, Wanpeng Li
2017-06-08 19:52 GMT+08:00 Paolo Bonzini <pbonzini@redhat.com>:
>
> 3) add an async_page_fault member to vcpu->arch.exception
Do you think we should also add an async_page_fault field to
x86_exception, then pass down to kvm_inject_page_fault() through
x86_exception? Maybe we should modify
kvm_queue_exception_e/kvm_multiple_exception etc to add an function
parameter for async_page_fault.
Regards,
Wanpeng Li
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH RFC] KVM: async_pf: fix async_pf exception injection
2017-06-09 5:30 ` Wanpeng Li
@ 2017-06-09 11:32 ` Paolo Bonzini
0 siblings, 0 replies; 6+ messages in thread
From: Paolo Bonzini @ 2017-06-09 11:32 UTC (permalink / raw)
To: Wanpeng Li; +Cc: linux-kernel, kvm, Radim Krčmář, Wanpeng Li
On 09/06/2017 07:30, Wanpeng Li wrote:
> 2017-06-08 19:52 GMT+08:00 Paolo Bonzini <pbonzini@redhat.com>:
>>
>> 3) add an async_page_fault member to vcpu->arch.exception
>
> Do you think we should also add an async_page_fault field to
> x86_exception, then pass down to kvm_inject_page_fault() through
> x86_exception? Maybe we should modify
> kvm_queue_exception_e/kvm_multiple_exception etc to add an function
> parameter for async_page_fault.
I don't know. :) I cannot say without looking closer or basically doing
all the work. Do whatever looks best to you!
Paolo
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2017-06-09 11:32 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2017-06-08 9:30 [PATCH RFC] KVM: async_pf: fix async_pf exception injection Wanpeng Li
2017-06-08 11:52 ` Paolo Bonzini
2017-06-08 12:32 ` Wanpeng Li
2017-06-08 12:48 ` Paolo Bonzini
2017-06-09 5:30 ` Wanpeng Li
2017-06-09 11:32 ` Paolo Bonzini
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