Re: [Xen-devel] [PATCH] x86/emulate: Check current->arch.vm_event in hvmemul_virtual_to_linear()

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 07.04.16 at 10:39, <rcojocaru@xxxxxxxxxxxxxxx> wrote:
> Theoretically it is possible for mem_access_emulate_each_rep to be
> true even when current->arch.vm_event == NULL, so add an extra
> check to hvmemul_virtual_to_linear().

Mind saying what those theoretical conditions are when this might
happen?

> --- a/xen/arch/x86/hvm/emulate.c
> +++ b/xen/arch/x86/hvm/emulate.c
> @@ -514,7 +514,7 @@ static int hvmemul_virtual_to_linear(
>       * vm_event being triggered for repeated writes to a whole page.
>       */
>      if ( unlikely(current->domain->arch.mem_access_emulate_each_rep) &&
> -         current->arch.vm_event->emulate_flags != 0 )
> +         current->arch.vm_event && current->arch.vm_event->emulate_flags != 
> 0 )

That's then the third instance of "current" here - this needs
latching into a local variable.

Jan


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