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| Started by | Matt Fleming <matt@codeblueprint.co.uk> |
|---|---|
| First post | 2016-09-13 17:00 +0200 |
| Last post | 2016-09-14 03:30 +0200 |
| Articles | 6 — 3 participants |
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KVM patches applied in weird order in -stable Matt Fleming <matt@codeblueprint.co.uk> - 2016-09-13 17:00 +0200
Re: KVM patches applied in weird order in -stable Greg KH <gregkh@linuxfoundation.org> - 2016-09-13 17:00 +0200
Re: KVM patches applied in weird order in -stable Paolo Bonzini <pbonzini@redhat.com> - 2016-09-13 18:30 +0200
Re: KVM patches applied in weird order in -stable Greg KH <gregkh@linuxfoundation.org> - 2016-09-13 19:00 +0200
Re: KVM patches applied in weird order in -stable Paolo Bonzini <pbonzini@redhat.com> - 2016-09-13 19:00 +0200
Re: KVM patches applied in weird order in -stable Greg KH <gregkh@linuxfoundation.org> - 2016-09-14 03:30 +0200
| From | Matt Fleming <matt@codeblueprint.co.uk> |
|---|---|
| Date | 2016-09-13 17:00 +0200 |
| Subject | KVM patches applied in weird order in -stable |
| Message-ID | <sgXlM-3gI-3@gated-at.bofh.it> |
Folks,
While hunting down a performance issue involving KVM I was surprised
to see "native_set_debugreg()" as the first entry in `perf top`.
Digging deeper, it looks as though the following patches were applied
in the wrong order in -stable. This is the order as they appear in
Linus' tree,
[0] commit 4e422bdd2f84 ("KVM: x86: fix missed hardware breakpoints")
[1] commit 172b2386ed16 ("KVM: x86: fix missed hardware breakpoints")
[2] commit 70e4da7a8ff6 ("KVM: x86: fix root cause for missed hardware breakpoints")
but this is the order for linux-4.4.y
[1] commit fc90441e728a ("KVM: x86: fix missed hardware breakpoints")
[2] commit 25e8618619a5 ("KVM: x86: fix root cause for missed hardware breakpoints")
[0] commit 0f6e5e26e68f ("KVM: x86: fix missed hardware breakpoints")
The upshot is that KVM_DEBUGREG_RELOAD is always set when returning
from kvm_arch_vcpu_load() in stable, but not in Linus' tree.
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| From | Greg KH <gregkh@linuxfoundation.org> |
|---|---|
| Date | 2016-09-13 17:00 +0200 |
| Message-ID | <sgXlM-3gI-25@gated-at.bofh.it> |
| In reply to | #1482555 |
[adding stable@ as this is a stable issue, not a 'normal' issue]
On Tue, Sep 13, 2016 at 03:51:00PM +0100, Matt Fleming wrote:
> Folks,
>
> While hunting down a performance issue involving KVM I was surprised
> to see "native_set_debugreg()" as the first entry in `perf top`.
>
> Digging deeper, it looks as though the following patches were applied
> in the wrong order in -stable. This is the order as they appear in
> Linus' tree,
>
> [0] commit 4e422bdd2f84 ("KVM: x86: fix missed hardware breakpoints")
> [1] commit 172b2386ed16 ("KVM: x86: fix missed hardware breakpoints")
> [2] commit 70e4da7a8ff6 ("KVM: x86: fix root cause for missed hardware breakpoints")
>
> but this is the order for linux-4.4.y
>
> [1] commit fc90441e728a ("KVM: x86: fix missed hardware breakpoints")
> [2] commit 25e8618619a5 ("KVM: x86: fix root cause for missed hardware breakpoints")
> [0] commit 0f6e5e26e68f ("KVM: x86: fix missed hardware breakpoints")
>
> The upshot is that KVM_DEBUGREG_RELOAD is always set when returning
> from kvm_arch_vcpu_load() in stable, but not in Linus' tree.
How would applying these in a different order cause breakage?
And if this is a problem, can you please send me a patch to fix it up?
thanks,
greg k-h
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| From | Paolo Bonzini <pbonzini@redhat.com> |
|---|---|
| Date | 2016-09-13 18:30 +0200 |
| Message-ID | <sgYKR-4ky-13@gated-at.bofh.it> |
| In reply to | #1482559 |
On 13/09/2016 16:58, Greg KH wrote:
> [adding stable@ as this is a stable issue, not a 'normal' issue]
>
> On Tue, Sep 13, 2016 at 03:51:00PM +0100, Matt Fleming wrote:
>> Folks,
>>
>> While hunting down a performance issue involving KVM I was surprised
>> to see "native_set_debugreg()" as the first entry in `perf top`.
>>
>> Digging deeper, it looks as though the following patches were applied
>> in the wrong order in -stable. This is the order as they appear in
>> Linus' tree,
>>
>> [0] commit 4e422bdd2f84 ("KVM: x86: fix missed hardware breakpoints")
>> [1] commit 172b2386ed16 ("KVM: x86: fix missed hardware breakpoints")
>> [2] commit 70e4da7a8ff6 ("KVM: x86: fix root cause for missed hardware breakpoints")
>>
>> but this is the order for linux-4.4.y
>>
>> [1] commit fc90441e728a ("KVM: x86: fix missed hardware breakpoints")
>> [2] commit 25e8618619a5 ("KVM: x86: fix root cause for missed hardware breakpoints")
>> [0] commit 0f6e5e26e68f ("KVM: x86: fix missed hardware breakpoints")
>>
>> The upshot is that KVM_DEBUGREG_RELOAD is always set when returning
>> from kvm_arch_vcpu_load() in stable, but not in Linus' tree.
>
> How would applying these in a different order cause breakage?
[2] is reverting [0]+[1]. Stable is not due to the different order.
> And if this is a problem, can you please send me a patch to fix it up?
Yup, on the way.
Paolo
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| From | Greg KH <gregkh@linuxfoundation.org> |
|---|---|
| Date | 2016-09-13 19:00 +0200 |
| Message-ID | <sgZdT-4vC-3@gated-at.bofh.it> |
| In reply to | #1482621 |
On Tue, Sep 13, 2016 at 06:26:12PM +0200, Paolo Bonzini wrote:
>
>
> On 13/09/2016 16:58, Greg KH wrote:
> > [adding stable@ as this is a stable issue, not a 'normal' issue]
> >
> > On Tue, Sep 13, 2016 at 03:51:00PM +0100, Matt Fleming wrote:
> >> Folks,
> >>
> >> While hunting down a performance issue involving KVM I was surprised
> >> to see "native_set_debugreg()" as the first entry in `perf top`.
> >>
> >> Digging deeper, it looks as though the following patches were applied
> >> in the wrong order in -stable. This is the order as they appear in
> >> Linus' tree,
> >>
> >> [0] commit 4e422bdd2f84 ("KVM: x86: fix missed hardware breakpoints")
> >> [1] commit 172b2386ed16 ("KVM: x86: fix missed hardware breakpoints")
> >> [2] commit 70e4da7a8ff6 ("KVM: x86: fix root cause for missed hardware breakpoints")
> >>
> >> but this is the order for linux-4.4.y
> >>
> >> [1] commit fc90441e728a ("KVM: x86: fix missed hardware breakpoints")
> >> [2] commit 25e8618619a5 ("KVM: x86: fix root cause for missed hardware breakpoints")
> >> [0] commit 0f6e5e26e68f ("KVM: x86: fix missed hardware breakpoints")
> >>
> >> The upshot is that KVM_DEBUGREG_RELOAD is always set when returning
> >> from kvm_arch_vcpu_load() in stable, but not in Linus' tree.
> >
> > How would applying these in a different order cause breakage?
>
> [2] is reverting [0]+[1]. Stable is not due to the different order.
Really? Are you sure that [0] and [1] isn't just the same commit? It
looks like that to me.
> > And if this is a problem, can you please send me a patch to fix it up?
>
> Yup, on the way.
thanks,
greg k-h
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| From | Paolo Bonzini <pbonzini@redhat.com> |
|---|---|
| Date | 2016-09-13 19:00 +0200 |
| Message-ID | <sgZdU-4vC-25@gated-at.bofh.it> |
| In reply to | #1482636 |
On 13/09/2016 18:57, Greg KH wrote:
>>>> > >> [0] commit 4e422bdd2f84 ("KVM: x86: fix missed hardware breakpoints")
>>>> > >> [1] commit 172b2386ed16 ("KVM: x86: fix missed hardware breakpoints")
>>>> > >> [2] commit 70e4da7a8ff6 ("KVM: x86: fix root cause for missed hardware breakpoints")
>>>> > >>
>>>> > >> but this is the order for linux-4.4.y
>>>> > >>
>>>> > >> [1] commit fc90441e728a ("KVM: x86: fix missed hardware breakpoints")
>>>> > >> [2] commit 25e8618619a5 ("KVM: x86: fix root cause for missed hardware breakpoints")
>>>> > >> [0] commit 0f6e5e26e68f ("KVM: x86: fix missed hardware breakpoints")
>>>> > >>
>>>> > >> The upshot is that KVM_DEBUGREG_RELOAD is always set when returning
>>>> > >> from kvm_arch_vcpu_load() in stable, but not in Linus' tree.
>>> > >
>>> > > How would applying these in a different order cause breakage?
>> >
>> > [2] is reverting [0]+[1]. Stable is not due to the different order.
> Really? Are you sure that [0] and [1] isn't just the same commit? It
> looks like that to me.
It is; "git" automatically resolved the conflicts when merging [1], and
then [2] reverted the change. In stable, changing the order created a
different conflict resolution.
Paolo
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| From | Greg KH <gregkh@linuxfoundation.org> |
|---|---|
| Date | 2016-09-14 03:30 +0200 |
| Message-ID | <sh7br-1xA-5@gated-at.bofh.it> |
| In reply to | #1482644 |
On Tue, Sep 13, 2016 at 06:58:40PM +0200, Paolo Bonzini wrote:
>
>
> On 13/09/2016 18:57, Greg KH wrote:
> >>>> > >> [0] commit 4e422bdd2f84 ("KVM: x86: fix missed hardware breakpoints")
> >>>> > >> [1] commit 172b2386ed16 ("KVM: x86: fix missed hardware breakpoints")
> >>>> > >> [2] commit 70e4da7a8ff6 ("KVM: x86: fix root cause for missed hardware breakpoints")
> >>>> > >>
> >>>> > >> but this is the order for linux-4.4.y
> >>>> > >>
> >>>> > >> [1] commit fc90441e728a ("KVM: x86: fix missed hardware breakpoints")
> >>>> > >> [2] commit 25e8618619a5 ("KVM: x86: fix root cause for missed hardware breakpoints")
> >>>> > >> [0] commit 0f6e5e26e68f ("KVM: x86: fix missed hardware breakpoints")
> >>>> > >>
> >>>> > >> The upshot is that KVM_DEBUGREG_RELOAD is always set when returning
> >>>> > >> from kvm_arch_vcpu_load() in stable, but not in Linus' tree.
> >>> > >
> >>> > > How would applying these in a different order cause breakage?
> >> >
> >> > [2] is reverting [0]+[1]. Stable is not due to the different order.
> > Really? Are you sure that [0] and [1] isn't just the same commit? It
> > looks like that to me.
>
> It is; "git" automatically resolved the conflicts when merging [1], and
> then [2] reverted the change. In stable, changing the order created a
> different conflict resolution.
Yes, given that I turn them into individual patches, the order I used
was really the only one that would work, and is how this happened :)
thanks,
greg k-h
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