lkml.org 
[lkml]   [2017]   [Jul]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v1] xen: get rid of paravirt op adjust_exception_frame
From
Date
On 26/07/17 15:48, Andy Lutomirski wrote:
> On Mon, Jul 24, 2017 at 7:28 AM, Juergen Gross <jgross@suse.com> wrote:
>> When running as Xen pv-guest the exception frame on the stack contains
>> %r11 and %rcx additional to the other data pushed by the processor.
>>
>> Instead of having a paravirt op being called for each exception type
>> prepend the Xen specific code to each exception entry. When running as
>> Xen pv-guest just use the exception entry with prepended instructions,
>> otherwise use the entry without the Xen specific code.
>
> I think this is a nice cleanup, but I'm wondering if it would be even
> nicer if the Xen part was kept out-of-line. That is, could Xen have
> little stubs like:
>
> xen_alignment_check:
> pop %rcx
> pop %r11
> jmp alignment_check
>
> rather than using the macros in entry_64.S that you have? Then you
> could adjust set_trap_gate instead of pack_gate and maybe even do
> something like:
>
> #define set_trap_gate(..., name, ...) set_native_or_xen_trap_gate(...,
> name, xen_##name, ...)

Okay.

>> /* Runs on exception stack */
>> -ENTRY(nmi)
>> - /*
>> - * Fix up the exception frame if we're on Xen.
>> - * PARAVIRT_ADJUST_EXCEPTION_FRAME is guaranteed to push at most
>> - * one value to the stack on native, so it may clobber the rdx
>> - * scratch slot, but it won't clobber any of the important
>> - * slots past it.
>> - *
>> - * Xen is a different story, because the Xen frame itself overlaps
>> - * the "NMI executing" variable.
>> - */
>
> I would keep this comment. The Xen frame really is in the way AFAICT.

Taking Andrew's comments into account I can drop it?


Juergen

\
 
 \ /
  Last update: 2017-07-26 17:13    [W:0.076 / U:20.456 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site