[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Legacy PCI interrupt {de}assertion count
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx] > Sent: Monday, March 27, 2017 4:00 PM > > >>> On 24.03.17 at 17:54, <roger.pau@xxxxxxxxxx> wrote: > > As I understand it, for level triggered legacy PCI interrupts Xen sets > > up a timer in order to perform the EOI if the guest takes too long in > > deasserting the line. This is done in pt_irq_time_out. What I don't > > understand is why this function also does a deassertion of the guest view > of the PCI interrupt, ie: > > why it calls hvm_pci_intx_deassert. This AFAICT will clear the pending > > assert in the guest, and thus the guest will end up loosing one interrupt. > > Especially with the comment next to the respective set_timer() it looks to me > as if this was the intended effect: If the guest didn't care to at least start > handling the interrupt within PT_IRQ_TIME_OUT, we want it look to be lost in > order to not have it block other interrupts inside the guest (i.e. there's > more > to it than just guarding the host here). > > "Luckily" commit 0f843ba00c ("vt-d: Allow pass-through of shared > interrupts") introducing this has no description at all. Let's see if Kevin > remembers any further details ... > Sorry I don't remember more detail other than existing comments. Roger, did you encounter a problem now? Thanks Kevin _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx https://lists.xen.org/xen-devel
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