From: "Jan Beulich" <JBeulich@suse.com>
To: Paul Durrant <Paul.Durrant@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>, "Keir (Xen.org)" <keir@xen.org>,
Andrew Cooper <Andrew.Cooper3@citrix.com>,
Stefano Stabellini <Stefano.Stabellini@citrix.com>,
Ian Jackson <Ian.Jackson@citrix.com>,
"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
Subject: Re: [PATCH v5 2/2] x86/hvm/viridian: Enable APIC assist enlightenment
Date: Fri, 18 Mar 2016 04:24:41 -0600 [thread overview]
Message-ID: <56EBE57902000078000DE476@prv-mh.provo.novell.com> (raw)
In-Reply-To: <c50120a6347c4c60a508d2c2e231f289@AMSPEX02CL03.citrite.net>
>>> On 18.03.16 at 11:06, <Paul.Durrant@citrix.com> wrote:
>> From: Jan Beulich [mailto:JBeulich@suse.com]
>> Sent: 17 March 2016 16:43
>> >>> On 17.03.16 at 13:13, <paul.durrant@citrix.com> wrote:
>> > @@ -1170,10 +1183,27 @@ int vlapic_has_pending_irq(struct vcpu *v)
>> > !nestedhvm_vcpu_in_guestmode(v) )
>> > return irr;
>> >
>> > + /*
>> > + * If APIC assist was used then there may have been no EOI so
>> > + * we need to clear the requisite bit from the ISR here, before
>> > + * comparing with the IRR.
>> > + */
>> > + if ( viridian_complete_apic_assist(v, &vector) &&
>> > + vector != -1 )
>>
>> Afaict "vector" is uninitialized here when initialize_apic_assist()
>> didn't run for that vCPU yet (which includes the case where no
>> Viridian emulation is active at all).
>>
>
> Yes, vector will be uninitialized in that case but viridian
> _complete_apic_assist() will return 0 (because the va will be zero) and so
> the second clause of the if will not be evaluated.
Ah, true. But raises the question why viridian_complete_apic_assist()
doesn't return the vector then rather then using indirection.
>> > + /*
>> > + * This vector is edge triggered and there are no lower priority
>> > + * vectors pending, so we can use APIC assist to avoid exiting
>> > + * for EOI.
>> > + */
>> > + viridian_start_apic_assist(v, vector);
>> >
>> > +done:
>>
>> Labels indented by at least one space please.
>
> OK, sorry, emacs keeps moving them back.
That's very unfriendly of it.
Jan
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next prev parent reply other threads:[~2016-03-18 10:24 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-17 12:13 [PATCH v4 0/2] x86/hvm/viridian: APIC assist Paul Durrant
2016-03-17 12:13 ` [PATCH v5 1/2] x86/hvm/viridian: keep APIC assist page mapped Paul Durrant
2016-03-17 12:13 ` [PATCH v5 2/2] x86/hvm/viridian: Enable APIC assist enlightenment Paul Durrant
2016-03-17 16:43 ` Jan Beulich
2016-03-18 10:06 ` Paul Durrant
2016-03-18 10:24 ` Jan Beulich [this message]
2016-03-18 10:30 ` Paul Durrant
2016-03-18 10:58 ` Ian Jackson
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