Re: [Xen-devel] [PATCH v11 for-xen-4.5 13/20] x86/VPMU: Save VPMU state for PV guests during context switch

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Tue, Sep 23, 2014 at 11:10:39AM -0400, Boris Ostrovsky wrote:
> On 09/23/2014 11:01 AM, Konrad Rzeszutek Wilk wrote:
> >On Mon, Sep 22, 2014 at 07:57:54PM -0400, Boris Ostrovsky wrote:
> >>Save VPMU state during context switch for both HVM and PV(H) guests.
> >>
> >>A subsequent patch will make it possible for vpmu_switch_to() to call
> >Could you say what is the name of the 'subsequent patch' in the commit
> >description please?
> 
> It's patch 19 where NMI PMU interrupts are added.

"x86/VPMU: NMI-based VPMU support" would look great in the commit
description.
> 
> >
> >>vmx_vmcs_try_enter()->vcpu_pause() which needs is_running to be correctly
> >>set/cleared. To prepare for that, call context_saved() before 
> >>vpmu_switch_to()
> >>is executed.
> >And what ramifications does that have to the guests if one only applied
> >patches up to this point?
> 
> None. Which is why I decided to make this change in this patch and not wait
> until patch 19.
> 

OK, please do spell it out in the patch so that Anxious Release Managers
don't have to sweat about regressions.

And with those changes:

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> -boris
> 
> >
> >>Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> >>---
> >>  xen/arch/x86/domain.c | 20 +++++++++-----------
> >>  1 file changed, 9 insertions(+), 11 deletions(-)
> >>
> >>diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
> >>index 5e492d8..d7fb99d 100644
> >>--- a/xen/arch/x86/domain.c
> >>+++ b/xen/arch/x86/domain.c
> >>@@ -1495,16 +1495,13 @@ void context_switch(struct vcpu *prev, struct vcpu 
> >>*next)
> >>      }
> >>      if ( prev != next )
> >>-        _update_runstate_area(prev);
> >>-
> >>-    if ( is_hvm_vcpu(prev) )
> >>      {
> >>-        if (prev != next)
> >>-            vpmu_switch_from(prev, next);
> >>+        _update_runstate_area(prev);
> >>+        vpmu_switch_from(prev, next);
> >>+    }
> >>-        if ( !list_empty(&prev->arch.hvm_vcpu.tm_list) )
> >>+    if ( is_hvm_vcpu(prev) && !list_empty(&prev->arch.hvm_vcpu.tm_list) )
> >>              pt_save_timer(prev);
> >>-    }
> >>      local_irq_disable();
> >>@@ -1543,15 +1540,16 @@ void context_switch(struct vcpu *prev, struct vcpu 
> >>*next)
> >>                             !is_hardware_domain(next->domain));
> >>      }
> >>-    if ( is_hvm_vcpu(prev) && (prev != next) )
> >>-        /* Must be done with interrupts enabled */
> >>-        vpmu_switch_to(prev, next);
> >>-
> >>      context_saved(prev);
> >>      if ( prev != next )
> >>+    {
> >>          _update_runstate_area(next);
> >>+        /* Must be done with interrupts enabled */
> >>+        vpmu_switch_to(prev, next);
> >>+    }
> >>+
> >>      /* Ensure that the vcpu has an up-to-date time base. */
> >>      update_vcpu_system_time(next);
> >>-- 
> >>1.8.1.4
> >>
> >>
> >>_______________________________________________
> >>Xen-devel mailing list
> >>Xen-devel@xxxxxxxxxxxxx
> >>http://lists.xen.org/xen-devel
> 

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