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Re: [Xen-devel] [PATCH] x86/traps: Correct overly-general assertion introduced in c/s d5c251c



On 14/12/16 12:52, Jan Beulich wrote:
>>>> On 14.12.16 at 12:35, <andrew.cooper3@xxxxxxxxxx> wrote:
>> The assertion about guest paging mode must only apply to guest pagefaults.
>>
>> This ASSERT() accidentally also trips if Xen takes a pagefault when in HVM
>> context, such as a copy_to_user() failure in the shadow pagetable code.
>>
>> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
>
> But isn't the other piece the original patch touched in the same
> function suffering a similar problem? I.e. can't this mis-trigger
> when dealing with a page fault in Xen while in the context of a
> HVM guest in log-dirty mode, and hence needs re-adding the
> !paging_mode_external() check (or alternatively using
> paging_mode_only_log_dirty() instead of paging_mode_log_dirty())?

Good point, although it should still be guest_mode() to be more clearly
avoiding the hypervisor case.

~Andrew

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