* [PATCH] KVM: No need to retry for hva_to_pfn_remapped()
@ 2020-04-16 15:59 Peter Xu
2020-05-04 16:59 ` Paolo Bonzini
0 siblings, 1 reply; 5+ messages in thread
From: Peter Xu @ 2020-04-16 15:59 UTC (permalink / raw)
To: kvm; +Cc: Paolo Bonzini, Sean Christopherson, Vitaly Kuznetsov, peterx
hva_to_pfn_remapped() calls fixup_user_fault(), which has already
handled the retry gracefully. Even if "unlocked" is set to true, it
means that we've got a VM_FAULT_RETRY inside fixup_user_fault(),
however the page fault has already retried and we should have the pfn
set correctly. No need to do that again.
Signed-off-by: Peter Xu <peterx@redhat.com>
---
virt/kvm/kvm_main.c | 5 -----
1 file changed, 5 deletions(-)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 2f1f2f56e93d..6aaed69641a5 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1824,8 +1824,6 @@ static int hva_to_pfn_remapped(struct vm_area_struct *vma,
r = fixup_user_fault(current, current->mm, addr,
(write_fault ? FAULT_FLAG_WRITE : 0),
&unlocked);
- if (unlocked)
- return -EAGAIN;
if (r)
return r;
@@ -1896,15 +1894,12 @@ static kvm_pfn_t hva_to_pfn(unsigned long addr, bool atomic, bool *async,
goto exit;
}
-retry:
vma = find_vma_intersection(current->mm, addr, addr + 1);
if (vma == NULL)
pfn = KVM_PFN_ERR_FAULT;
else if (vma->vm_flags & (VM_IO | VM_PFNMAP)) {
r = hva_to_pfn_remapped(vma, addr, write_fault, writable, &pfn);
- if (r == -EAGAIN)
- goto retry;
if (r < 0)
pfn = KVM_PFN_ERR_FAULT;
} else {
--
2.24.1
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH] KVM: No need to retry for hva_to_pfn_remapped()
2020-04-16 15:59 [PATCH] KVM: No need to retry for hva_to_pfn_remapped() Peter Xu
@ 2020-05-04 16:59 ` Paolo Bonzini
2020-05-08 2:25 ` Peter Xu
0 siblings, 1 reply; 5+ messages in thread
From: Paolo Bonzini @ 2020-05-04 16:59 UTC (permalink / raw)
To: Peter Xu, kvm; +Cc: Sean Christopherson, Vitaly Kuznetsov
On 16/04/20 17:59, Peter Xu wrote:
> hva_to_pfn_remapped() calls fixup_user_fault(), which has already
> handled the retry gracefully. Even if "unlocked" is set to true, it
> means that we've got a VM_FAULT_RETRY inside fixup_user_fault(),
> however the page fault has already retried and we should have the pfn
> set correctly. No need to do that again.
>
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
> virt/kvm/kvm_main.c | 5 -----
> 1 file changed, 5 deletions(-)
>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 2f1f2f56e93d..6aaed69641a5 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -1824,8 +1824,6 @@ static int hva_to_pfn_remapped(struct vm_area_struct *vma,
> r = fixup_user_fault(current, current->mm, addr,
> (write_fault ? FAULT_FLAG_WRITE : 0),
> &unlocked);
> - if (unlocked)
> - return -EAGAIN;
> if (r)
> return r;
>
> @@ -1896,15 +1894,12 @@ static kvm_pfn_t hva_to_pfn(unsigned long addr, bool atomic, bool *async,
> goto exit;
> }
>
> -retry:
> vma = find_vma_intersection(current->mm, addr, addr + 1);
>
> if (vma == NULL)
> pfn = KVM_PFN_ERR_FAULT;
> else if (vma->vm_flags & (VM_IO | VM_PFNMAP)) {
> r = hva_to_pfn_remapped(vma, addr, write_fault, writable, &pfn);
> - if (r == -EAGAIN)
> - goto retry;
> if (r < 0)
> pfn = KVM_PFN_ERR_FAULT;
> } else {
>
Queued, thanks.
Paolo
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] KVM: No need to retry for hva_to_pfn_remapped()
2020-05-04 16:59 ` Paolo Bonzini
@ 2020-05-08 2:25 ` Peter Xu
2020-05-08 7:07 ` Paolo Bonzini
2020-05-29 9:45 ` Paolo Bonzini
0 siblings, 2 replies; 5+ messages in thread
From: Peter Xu @ 2020-05-08 2:25 UTC (permalink / raw)
To: Paolo Bonzini; +Cc: kvm, Sean Christopherson, Vitaly Kuznetsov
On Mon, May 04, 2020 at 06:59:30PM +0200, Paolo Bonzini wrote:
> On 16/04/20 17:59, Peter Xu wrote:
> > hva_to_pfn_remapped() calls fixup_user_fault(), which has already
> > handled the retry gracefully. Even if "unlocked" is set to true, it
> > means that we've got a VM_FAULT_RETRY inside fixup_user_fault(),
> > however the page fault has already retried and we should have the pfn
> > set correctly. No need to do that again.
> >
> > Signed-off-by: Peter Xu <peterx@redhat.com>
> > ---
> > virt/kvm/kvm_main.c | 5 -----
> > 1 file changed, 5 deletions(-)
> >
> > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> > index 2f1f2f56e93d..6aaed69641a5 100644
> > --- a/virt/kvm/kvm_main.c
> > +++ b/virt/kvm/kvm_main.c
> > @@ -1824,8 +1824,6 @@ static int hva_to_pfn_remapped(struct vm_area_struct *vma,
> > r = fixup_user_fault(current, current->mm, addr,
> > (write_fault ? FAULT_FLAG_WRITE : 0),
> > &unlocked);
> > - if (unlocked)
> > - return -EAGAIN;
> > if (r)
> > return r;
> >
> > @@ -1896,15 +1894,12 @@ static kvm_pfn_t hva_to_pfn(unsigned long addr, bool atomic, bool *async,
> > goto exit;
> > }
> >
> > -retry:
> > vma = find_vma_intersection(current->mm, addr, addr + 1);
> >
> > if (vma == NULL)
> > pfn = KVM_PFN_ERR_FAULT;
> > else if (vma->vm_flags & (VM_IO | VM_PFNMAP)) {
> > r = hva_to_pfn_remapped(vma, addr, write_fault, writable, &pfn);
> > - if (r == -EAGAIN)
> > - goto retry;
> > if (r < 0)
> > pfn = KVM_PFN_ERR_FAULT;
> > } else {
> >
>
> Queued, thanks.
Paolo, Is it still possible to unqueue this patch? I overlooked the fact that
if unlocked==true then the vma pointer could be invalidated, so the 2nd
follow_pfn() is potentially racy. Sorry for the trouble!
--
Peter Xu
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] KVM: No need to retry for hva_to_pfn_remapped()
2020-05-08 2:25 ` Peter Xu
@ 2020-05-08 7:07 ` Paolo Bonzini
2020-05-29 9:45 ` Paolo Bonzini
1 sibling, 0 replies; 5+ messages in thread
From: Paolo Bonzini @ 2020-05-08 7:07 UTC (permalink / raw)
To: Peter Xu; +Cc: kvm, Sean Christopherson, Vitaly Kuznetsov
On 08/05/20 04:25, Peter Xu wrote:
>> Queued, thanks.
>
> Paolo, Is it still possible to unqueue this patch? I overlooked the fact that
> if unlocked==true then the vma pointer could be invalidated, so the 2nd
> follow_pfn() is potentially racy. Sorry for the trouble!
>
Sure, thanks.
Paolo
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] KVM: No need to retry for hva_to_pfn_remapped()
2020-05-08 2:25 ` Peter Xu
2020-05-08 7:07 ` Paolo Bonzini
@ 2020-05-29 9:45 ` Paolo Bonzini
1 sibling, 0 replies; 5+ messages in thread
From: Paolo Bonzini @ 2020-05-29 9:45 UTC (permalink / raw)
To: Peter Xu; +Cc: kvm, Sean Christopherson, Vitaly Kuznetsov
On 08/05/20 04:25, Peter Xu wrote:
> Even if "unlocked" is set to true, it
> means that we've got a VM_FAULT_RETRY inside fixup_user_fault(),
I have just reverted it. Thanks!
Paolo
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2020-05-29 9:45 UTC | newest]
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2020-04-16 15:59 [PATCH] KVM: No need to retry for hva_to_pfn_remapped() Peter Xu
2020-05-04 16:59 ` Paolo Bonzini
2020-05-08 2:25 ` Peter Xu
2020-05-08 7:07 ` Paolo Bonzini
2020-05-29 9:45 ` Paolo Bonzini
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