[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH for-4.13] x86/vmx: always sync PIR to IRR before vmentry
> From: Roger Pau Monné [mailto:roger.pau@xxxxxxxxxx] > Sent: Thursday, November 21, 2019 5:26 PM > > On Mon, Nov 18, 2019 at 05:00:29PM +0100, Jan Beulich wrote: > > On 18.11.2019 15:20, Roger Pau Monné wrote: > > > On Mon, Nov 18, 2019 at 03:00:00PM +0100, Jan Beulich wrote: > > >> On 18.11.2019 14:46, Roger Pau Monné wrote: > > >>> On Mon, Nov 18, 2019 at 01:01:58PM +0100, Jan Beulich wrote: > > >>>> On 18.11.2019 11:16, Roger Pau Monne wrote: > > >>>>> When using posted interrupts on Intel hardware it's possible that > the > > >>>>> vCPU resumes execution with a stale local APIC IRR register > because > > >>>>> depending on the interrupts to be injected vlapic_has_pending_irq > > >>>>> might not be called, and thus PIR won't be synced into IRR. > > >>>>> > > >>>>> Fix this by making sure PIR is always synced to IRR in > vmx_intr_assist > > >>>>> regardless of what interrupts are pending. > > >>>> > > >>>> For this part, did you consider pulling ahead to the beginning > > >>>> of hvm_vcpu_has_pending_irq() its call to vlapic_has_pending_irq()? > > >>> > > >>> I assumed the order in hvm_vcpu_has_pending_irq is there for a > reason. > > >>> I could indeed move vlapic_has_pending_irq to the top, but then > either > > >>> the result is discarded if for example a NMI is pending injection > > >>> (in which case there's no need to go through all the logic in > > >>> vlapic_has_pending_irq), or we invert the priority of event > > >>> injection. > > >> > > >> Changing the order of events injected is not an option afaict. The > > >> pointless processing done is a valid concern, yet the suggestion > > >> was specifically to have (part of) this processing to occur early. > > >> The discarding of the result, in turn, is not a problem afaict, as > > >> a subsequent call will return the same result (unless a higher > > >> priority interrupt has surfaced in the meantime). > > > > > > Yes, that's fine. So you would prefer to move the call to > > > vlapic_has_pending_irq before any exit path in > > > hvm_vcpu_has_pending_irq? > > > > "Prefer" isn't really the way I would put it. I'd like this to be > > considered as an alternative because, as said, I think the current > > placement look more like a plaster than a cure. I'm also open for > > other suggestions. But first of all I'd like to see what the VMX > > maintainers think. > > Kevin/Jun, can we please get your opinion on the above item? Give me some time to catch up... Thanks Kevin _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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