[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] x86: clean up __io_apic_eoi()
On 14/11/11 09:08, Jan Beulich wrote: >>>> On 11.11.11 at 17:49, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote: >> On 11/11/11 16:07, Jan Beulich wrote: >>> Irrespective of the IO-APIC vector sharing suppression patch just sent >>> the logic in this function needs to iterate over all RTEs, since >>> multiple pins within an IO-APIC may still use the same vector. >> Why? The whole point of preventing vector sharing for IO-APICs is to >> prevent two or more RTEs referencing the same vector. > If that was really the case on *all* systems, then we wouldn't need > the chains of IRQs hanging off irq_2_pin[] entries. Obviously there are > or have been or could theoretically be systems that do make use of this. > > BUT again after some more thinking about this over the weekend > (and after fixing the issue pointed out in the other response regarding > the other patch) I think we can actually convert the function to > behave the way you intended it to after dealing with the vector > sharing issue: The call sites are then only __eoi_IO_APIC_irq() (which > already traverses the chain from irq_2_pin[]) and clear_IO_APIC_pin() > (which explicitly wants to deal with just a single (apic, pin) tuple, the > uses in the timer interrupt related boot time code having been bogus in > this respect even before your original change to the EOI logic, as they > imply that no other (apic, pin) tuple also represents the timer IRQ). > > Jan > Ah yes. I was silly and had not considered that possibility. Realistically, I doubt there are many boxes still around which have shared ISA interrupts, but we should deal with the case. -- Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer T: +44 (0)1223 225 900, http://www.citrix.com _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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