Re: [Xen-devel] [PATCH v6 08/18] vmx: Suppress posting interrupts when 'SN' is set

[Jan Beulich]

>>> On 06.09.15 at 04:33,  wrote:
>> From: Jan Beulich [mailto:jbeul...@suse.com]
>> Sent: Friday, September 04, 2015 10:53 PM
>> >>> On 25.08.15 at 03:57,  wrote:
>> > --- a/xen/arch/x86/hvm/vmx/vmx.c
>> > +++ b/xen/arch/x86/hvm/vmx/vmx.c
>> > @@ -1701,8 +1701,36 @@ static void vmx_deliver_posted_intr(struct vcpu
>> *v, u8 vector)
>> >   */
>> >  pi_set_on(>arch.hvm_vmx.pi_desc);
>> >  }
>> > -else if ( !pi_test_and_set_on(>arch.hvm_vmx.pi_desc) )
>> > +else
>> >  {
>> > +struct pi_desc old, new, prev;
>> > +
>> > +/* To skip over first check in the loop below. */
>> > +prev.control = 0;
>> 
>> Why don't you just read the field instead of adding the comment?
> 
> What do you mean by "read the field"? Could you please elaborate it?

prev.control = v->arch.hvm_vmx.pi_desc.control;

Jan



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Re: [Xen-devel] [PATCH v6 08/18] vmx: Suppress posting interrupts when 'SN' is set

[Wu, Feng]

> -Original Message-
> From: Jan Beulich [mailto:jbeul...@suse.com]
> Sent: Friday, September 04, 2015 10:53 PM
> To: Wu, Feng
> Cc: Andrew Cooper; Tian, Kevin; xen-devel@lists.xen.org; Keir Fraser
> Subject: Re: [PATCH v6 08/18] vmx: Suppress posting interrupts when 'SN' is 
> set
> 
> >>> On 25.08.15 at 03:57,  wrote:
> > --- a/xen/arch/x86/hvm/vmx/vmx.c
> > +++ b/xen/arch/x86/hvm/vmx/vmx.c
> > @@ -1701,8 +1701,36 @@ static void vmx_deliver_posted_intr(struct vcpu
> *v, u8 vector)
> >   */
> >  pi_set_on(>arch.hvm_vmx.pi_desc);
> >  }
> > -else if ( !pi_test_and_set_on(>arch.hvm_vmx.pi_desc) )
> > +else
> >  {
> > +struct pi_desc old, new, prev;
> > +
> > +/* To skip over first check in the loop below. */
> > +prev.control = 0;
> 
> Why don't you just read the field instead of adding the comment?

What do you mean by "read the field"? Could you please elaborate it?

Thanks,
Feng

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Re: [Xen-devel] [PATCH v6 08/18] vmx: Suppress posting interrupts when 'SN' is set

[Jan Beulich]

>>> On 25.08.15 at 03:57,  wrote:
> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -1701,8 +1701,36 @@ static void vmx_deliver_posted_intr(struct vcpu *v, u8 
> vector)
>   */
>  pi_set_on(>arch.hvm_vmx.pi_desc);
>  }
> -else if ( !pi_test_and_set_on(>arch.hvm_vmx.pi_desc) )
> +else
>  {
> +struct pi_desc old, new, prev;
> +
> +/* To skip over first check in the loop below. */
> +prev.control = 0;

Why don't you just read the field instead of adding the comment?

> +do {
> +/*
> + * Currently, we don't support urgent interrupt, all
> + * interrupts are recognized as non-urgent interrupt,
> + * so we cannot send posted-interrupt when 'SN' is set.
> + * Besides that, if 'ON' is already set, we cannot set
> + * posted-interrupts as well.
> + */
> +if ( pi_test_sn() || pi_test_on() )
> +{
> +vcpu_kick(v);
> +return;
> +}
> +
> +old.control = v->arch.hvm_vmx.pi_desc.control &
> +  ~( 1 << POSTED_INTR_ON | 1 << POSTED_INTR_SN );
> +new.control = v->arch.hvm_vmx.pi_desc.control |
> +  1 << POSTED_INTR_ON;

Missing parentheses around the shifts. In the former case there are
also stray blanks inside the parentheses.

Jan


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