Re: [Xen-devel] [PATCH 09/15] x86/emul: Avoid raising faults behind the emulators back

[Tim Deegan <tim@xxxxxxx>]

At 15:38 +0000 on 23 Nov (1479915532), Andrew Cooper wrote:
> Introduce a new x86_emul_pagefault() similar to x86_emul_hw_exception(), and
> use this instead of hvm_inject_page_fault() from emulation codepaths.
> 
> Replace one hvm_inject_hw_exception() in the shadow emulation codepaths.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

> NOTE: this is a functional change for the shadow code, as a #PF previously
> raised properly with the guest will now cause X86EMUL_UNHANDLABLE. It is my
> understanding after a discusion with Tim that this is ok, but I haven't done
> extenstive testing yet.

Do you plan to?  I think this is indeed OK, but there may be some edge
case, e.g. an instruction that writes to both the current top-level
pagetable (which can't be unshadowed) and an unmapped virtual address.
That ought to raise #PF in the guest but might now spin retrying?  

Tim.

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