[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: [Xen-devel] IRQ range in domain 0
1. The APIC that is included in almost every CPU produced today (certainly all PC processors produced today) is capable of more than 15 inputs (as I understand it, there's 256 "inputs". 2. Interupts with numbers higher than 256 are "virtual interrupts", which is a "XEN thing", and they are not REAL interrupts from hardware, but signalling within XEN to (for example) wake up another Domain. This is to the best of my understanding, and I have spent no time trying to trace, understand or research any of this, so if you're going to use any of the above for anything serious, I suggest you do some reasearch to confirm or revise the above statements. -- Mats > -----Original Message----- > From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx > [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of John Que > Sent: 25 August 2005 12:13 > To: Xen-devel@xxxxxxxxxxxxxxxxxxx > Subject: [Xen-devel] IRQ range in domain 0 > > Hello, > I am running Xen-Unstable on intel x386 , with one CPU ; > When running cat /proc/interrupts on Domain 0 I see the following: > > CPU0 > 1: 1424 Phys-irq i8042 > 9: 0 Phys-irq acpi > 14: 421055 Phys-irq ide0 > 15: 16 Phys-irq ide1 > 17: 4419 Phys-irq eth0 > 20: 10884 Phys-irq ohci_hcd:usb1 > 21: 0 Phys-irq ohci_hcd:usb2 > 256: 0 Dynamic-irq ctrl-if > 257: 77411 Dynamic-irq timer0 > 258: 0 Dynamic-irq console > 259: 0 Dynamic-irq net-be-dbg > NMI: 0 > LOC: 0 > ERR: 0 > MIS: 0 > > can I deduce from this that the number of available physical > IRQ is higher than 15? > What is strange to me is that on an ordinary linux kernel > (not a xen-patched kernel ) , there can be up to 15 > interrupts,and in all cases I know, they are in the range 0-14. > I don't remeber I saw a phiyscal interrupt whose number is > higher than 14 on a standard x386 platform. > > Also according to "Unerstanding the Linux Kernel" book,chapter 4: > "Tradional PICs are implemented by connecting "in cascade" > two 8259A-style external chips.Each chip can handle up to > eight different IRQ input lines. Since the INT output line of > the slave PIC is connected to the IRQ2 pin of the master PIC, > the number of available IRQ lines is limited to 15." > > > Any ideas? > Regards > John Que. > > _______________________________________________ > Xen-devel mailing list > Xen-devel@xxxxxxxxxxxxxxxxxxx > http://lists.xensource.com/xen-devel > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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