From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julien Grall Subject: Re: [PATCH v8 13/13] gic_remove_from_queues: take a lock on the right vcpu Date: Sun, 25 May 2014 18:37:05 +0100 Message-ID: <53822A41.5010302@linaro.org> References: <1400761950-25035-13-git-send-email-stefano.stabellini@eu.citrix.com> <537E2166.1060401@linaro.org> <537E3DA0.7060007@linaro.org> <537F898D.3090205@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Stefano Stabellini Cc: julien.grall@citrix.com, xen-devel@lists.xensource.com, Ian.Campbell@citrix.com List-Id: xen-devel@lists.xenproject.org On 25/05/14 16:39, Stefano Stabellini wrote: > That is actually the problem: if vcpu1 is the one enabling an SPI, the > target vcpu should still be the one specified by itarget. Yes, but by enabling I mean writing in ISENABLER* on VCPU1. In this case, we may inject this IRQ on this CPUs (see vgic_enable_irqs). > >> This can inject the IRQ in VCPU1 while it's already injected in >> VCPU0 (assuming the IRQ what disable for a little time). >> >>> >>>> BTW, for your todo: >>>> >>>>> + /* TODO: evict the irq from LRs */ >>>> >>>> We should not evict the IRQ from LRs. The guest may disable the IRQ while he >>>> is in the IRQ context (and before the IRQ has been EOI). If you drop the IRQs >>>> from the LRs, this can result to a maintenance interrupt: >>>> >>>> "If the specified Interrupt does not exist in the >>>> List registers, the GICH_HCR.EOIcount field is incremented, potentially >>>> generating a maintenance interrupt." >>> >>> It is still better than the alternative: having an LR busy for no reason. >>> A maintenance interrupt would be harmless. >> >> Our internal representation (in the status field, still inflight) won't >> be update-to-date for IRQ. We either inject a spurious IRQ (if it's a >> virtual IRQ), other set active & pending is physical IRQ (which is >> invalid from the GIC specification). > > I think that the best behaviour would be to evict the irq from LRs if > the irq is not active. Right. Regards, -- Julien Grall