Messages in this thread | | | Subject | Re: New vsyscall emulation breaks JITs | From | Suresh Siddha <> | Date | Tue, 09 Aug 2011 15:27:24 -0700 |
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On Fri, 2011-08-05 at 17:32 -0700, H. Peter Anvin wrote: > On 08/05/2011 05:20 PM, Andrew Lutomirski wrote: > > > > I was thinking of 0x20 - 0x39. 0x40, 0x41, and 0x42 should do the > > trick. I'll cook up a patch. > > > > If you want to keep those vectors available for devices as well, we > > could hook do_general_protection instead, but that's a little messy. > > Are there x86 machines out there that are starved for interrupt > > vectors? > > > > Yes, but 3 aren't going to matter much. > > However, on systems which have interrupt migration enabled we're not > using 0x21-0x2f for anything (because we need a single interrupt with > absolutely lowest priority).
Double checked to make sure and we actually allow 0x21-0x2f to be used for device interrupts (commit 6579b474572fd54c583ac074e8e7aaae926c62ef). So reserving the vectors in this range should be same as reserving in any other range available for use.
Thanks.
> Out of that range, there are a couple of > values which should be safe to use because they would be harmless > instructions of various forms: > > 0x24 - AND AL, imm8 > 0x25 - AND EAX, imm32 > 0x26 - ES: > 0x2C - SUB AL, imm8 > 0x2D - SUB EAX, imm32 > 0x2E - CS: > > [Cc: Suresh who is the expert on the interrupt assignments] > > -hpa
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