Re: [Xen-devel] [PATCH 11/13] x86/paravirt: Add paravirt alternatives infrastructure

[Boris Ostrovsky]

On 10/17/2017 04:17 PM, Josh Poimboeuf wrote:
> On Tue, Oct 17, 2017 at 11:36:57AM -0400, Boris Ostrovsky wrote:
>> On 10/17/2017 10:36 AM, Josh Poimboeuf wrote:
>>> Maybe we can add a new field to the alternatives entry struct which
>>> specifies the offset to the CALL instruction, so apply_alternatives()
>>> can find it.
>> We'd also have to assume that the restore part of an alternative entry
>> is the same size as the save part. Which is true now.
> Why?
>

Don't you need to know the size of the instruction without save and
restore part?

+ if (a->replacementlen == 6 && *insnbuf == 0xff && *(insnbuf+1) == 0x15)

Otherwise you'd need another field for the actual instruction length.

-boris