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Re: [Xen-devel] [PATCH 11/13] x86/paravirt: Add paravirt alternatives infrastructure
- To: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
- From: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
- Date: Tue, 17 Oct 2017 16:36:00 -0400
- Cc: Juergen Gross <jgross@xxxxxxxx>, Mike Galbraith <efault@xxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Peter Zijlstra <peterz@xxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Rusty Russell <rusty@xxxxxxxxxxxxxxx>, virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx, x86@xxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, Chris Wright <chrisw@xxxxxxxxxxxx>, live-patching@xxxxxxxxxxxxxxx, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>, Borislav Petkov <bp@xxxxxxxxx>, Andy Lutomirski <luto@xxxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Sasha Levin <alexander.levin@xxxxxxxxxxx>, Jiri Slaby <jslaby@xxxxxxx>, Alok Kataria <akataria@xxxxxxxxxx>
- Delivery-date: Tue, 17 Oct 2017 20:35:24 +0000
- List-id: Xen developer discussion <xen-devel.lists.xen.org>
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
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