Messages in this thread | | | Subject | Re: [PATCH v1] xen: get rid of paravirt op adjust_exception_frame | From | Juergen Gross <> | Date | Wed, 26 Jul 2017 17:12:46 +0200 |
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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
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