At 16:40 +0000 on 23 Nov (1479919254), Andrew Cooper wrote: > On 23/11/16 16:31, Tim Deegan wrote: > > 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.coop...@citrix.com> > >> 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? > > That is a devious corner case. I take it you have been there before?
In similar situations, yes. :) > The more I think about these changes, the more I think that the shadow > code would be better by selectively looking a pending event, injecting > pagefaults, but rejecting and retrying if any other event shows up. That sounds like a good idea, and seems like the smallest deviation from the current behaviour. It might also be OK to inject any event that the emulator raises. That's a bigger change but maybe a more coherent end result? Cheers, Tim. _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel
