Re: [Xen-devel] [PATCH v8 1/7] VMX: Permanently assign PI hook vmx_pi_switch_to()

["Wu, Feng" <feng.wu@xxxxxxxxx>]

> -----Original Message-----
> From: Tian, Kevin
> Sent: Friday, November 18, 2016 11:14 AM
> To: Wu, Feng <feng.wu@xxxxxxxxx>; xen-devel@xxxxxxxxxxxxx
> Cc: jbeulich@xxxxxxxx; andrew.cooper3@xxxxxxxxxx;
> george.dunlap@xxxxxxxxxxxxx; dario.faggioli@xxxxxxxxxx
> Subject: RE: [PATCH v8 1/7] VMX: Permanently assign PI hook
> vmx_pi_switch_to()
> 
> > From: Wu, Feng
> > Sent: Friday, November 18, 2016 9:57 AM
> >
> > PI hook vmx_pi_switch_to() is needed even when any previously
> 
> even when -> even after
> 
> > assigned device is detached from the domain. Since 'SN' bit is
> > also used to control the CPU side PI and we change the state of
> > SN bit in these two functions, then evaluate this bit in
> 
> which two functions?

vmx_pi_switch_to() and vmx_pi_switch_from(), I will explicitly
describe it in the next version.

Thanks,
Feng

> 
> > vmx_deliver_posted_intr() when trying to deliver the interrupt
> > in posted way via software. The problem is if we deassign the
> > hooks while the vCPU is runnable in the runqueue with 'SN' set,
> > all the furture notificaton event will be suppressed. This patch
> > makes the hook permanently assigned.
> >
> > Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx>
> > Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> > ---
> > v8:
> > - Comments changes
> >
> > v7:
> > - comments changes.
> >
> > v6:
> > - Adjust the comments and wording.
> >
> > v5:
> > - Zap "pi_switch_from" hook
> >
> > v4:
> > - Don't zap vmx_pi_switch_from() and vmx_pi_switch_to() when
> > any previously assigned device is detached from the domain.
> > - Comments changes.
> >
> >  xen/arch/x86/hvm/vmx/vmx.c | 8 +++++++-
> >  1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
> > index 3d330b6..f3911f2 100644
> > --- a/xen/arch/x86/hvm/vmx/vmx.c
> > +++ b/xen/arch/x86/hvm/vmx/vmx.c
> > @@ -222,8 +222,14 @@ void vmx_pi_hooks_deassign(struct domain *d)
> >
> >      d->arch.hvm_domain.vmx.vcpu_block = NULL;
> >      d->arch.hvm_domain.vmx.pi_switch_from = NULL;
> > -    d->arch.hvm_domain.vmx.pi_switch_to = NULL;
> >      d->arch.hvm_domain.vmx.pi_do_resume = NULL;
> > +
> > +    /*
> > +     * In fact, we could set 'd->arch.hvm_domain.vmx.pi_switch_to' to NULL
> > +     * in vmx_pi_switch_to() if no new device is in the process of getting
> > +     * assigned and "from" hook is NULL. However, it is not straightforward
> > +     * to find a clear solution, so just leave it here.
> > +     */
> 
> better to move this comment ahead of earlier zaps? Also seems the
> comment is different from what commit msg says. Please make
> them correlated.

Sure.

Thanks,
Feng

> 
> >  }
> >
> >  static int vmx_domain_initialise(struct domain *d)
> > --
> > 2.1.0


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