* KVM patches applied in weird order in -stable
@ 2016-09-13 14:51 Matt Fleming
2016-09-13 14:58 ` Greg KH
0 siblings, 1 reply; 6+ messages in thread
From: Matt Fleming @ 2016-09-13 14:51 UTC (permalink / raw)
To: Greg KH, Paolo Bonzini; +Cc: linux-kernel
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.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: KVM patches applied in weird order in -stable
2016-09-13 14:51 KVM patches applied in weird order in -stable Matt Fleming
@ 2016-09-13 14:58 ` Greg KH
2016-09-13 16:26 ` Paolo Bonzini
0 siblings, 1 reply; 6+ messages in thread
From: Greg KH @ 2016-09-13 14:58 UTC (permalink / raw)
To: Matt Fleming; +Cc: Paolo Bonzini, linux-kernel, stable
[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
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: KVM patches applied in weird order in -stable
2016-09-13 14:58 ` Greg KH
@ 2016-09-13 16:26 ` Paolo Bonzini
2016-09-13 16:57 ` Greg KH
0 siblings, 1 reply; 6+ messages in thread
From: Paolo Bonzini @ 2016-09-13 16:26 UTC (permalink / raw)
To: Greg KH, Matt Fleming; +Cc: linux-kernel, stable
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
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: KVM patches applied in weird order in -stable
2016-09-13 16:26 ` Paolo Bonzini
@ 2016-09-13 16:57 ` Greg KH
2016-09-13 16:58 ` Paolo Bonzini
0 siblings, 1 reply; 6+ messages in thread
From: Greg KH @ 2016-09-13 16:57 UTC (permalink / raw)
To: Paolo Bonzini; +Cc: Matt Fleming, linux-kernel, stable
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
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: KVM patches applied in weird order in -stable
2016-09-13 16:57 ` Greg KH
@ 2016-09-13 16:58 ` Paolo Bonzini
2016-09-14 1:19 ` Greg KH
0 siblings, 1 reply; 6+ messages in thread
From: Paolo Bonzini @ 2016-09-13 16:58 UTC (permalink / raw)
To: Greg KH; +Cc: Matt Fleming, linux-kernel, stable
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
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: KVM patches applied in weird order in -stable
2016-09-13 16:58 ` Paolo Bonzini
@ 2016-09-14 1:19 ` Greg KH
0 siblings, 0 replies; 6+ messages in thread
From: Greg KH @ 2016-09-14 1:19 UTC (permalink / raw)
To: Paolo Bonzini; +Cc: Matt Fleming, linux-kernel, stable
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
^ permalink raw reply [flat|nested] 6+ messages in thread
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2016-09-13 14:51 KVM patches applied in weird order in -stable Matt Fleming
2016-09-13 14:58 ` Greg KH
2016-09-13 16:26 ` Paolo Bonzini
2016-09-13 16:57 ` Greg KH
2016-09-13 16:58 ` Paolo Bonzini
2016-09-14 1:19 ` Greg KH
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