linux-kernel - Re: [PATCH v3 49/59] KVM: arm/arm64: GICv4: Propagate VLPI properties at map time

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Message-ID: <20170830201225.GM24522@cbox>
Date:   Wed, 30 Aug 2017 22:12:25 +0200
From:   Christoffer Dall <cdall@...aro.org>
To:     Marc Zyngier <marc.zyngier@....com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kvmarm@...ts.cs.columbia.edu, kvm@...r.kernel.org,
        Christoffer Dall <christoffer.dall@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Eric Auger <eric.auger@...hat.com>,
        Shanker Donthineni <shankerd@...eaurora.org>,
        Mark Rutland <mark.rutland@....com>,
        Shameerali Kolothum Thodi 
        <shameerali.kolothum.thodi@...wei.com>
Subject: Re: [PATCH v3 49/59] KVM: arm/arm64: GICv4: Propagate VLPI
 properties at map time

On Wed, Aug 30, 2017 at 03:56:57PM +0100, Marc Zyngier wrote:
> On 28/08/17 19:18, Christoffer Dall wrote:
> > On Mon, Jul 31, 2017 at 06:26:27PM +0100, Marc Zyngier wrote:
> >> When the VLPI gets mapped, it must inherit the configuration of
> >> LPI configured at the vITS level. FOr that purpose, let's make
> > 
> > *the LPI
> > *For that
> 
> Will fix, thanks.
> 
> > 
> >> update_lpi_config globally available and call it just after
> >> having performed the VLPI map operation.
> >>
> > 
> > I assume this means that the GIC compares the priorities of virtual
> > interrupts in the LRs with the priorities of the pending VLPIs and
> > figures out what to signal first?  I couldn't find anywhere in the spec
> > where this is explicitly stated.
> 
> There is this mention in IHI0069D, 5.4 (Virtual LPI support):
> 
> "The Redistributor associated with the PE on which the vPE is scheduled
> determines the highest priority pending vLPI, and forwards this to the
> virtual CPU interface of the vPE. This vLPI and the interrupts in the
> List register are then prioritized together to determine the highest
> priority pending virtual interrupt for the vPE."
> 

Wow, I didn't find that staring at the manual for a considerable amount
of time.  Thanks for the pointer.

Thanks,
-Christoffer