Re: [Xen-devel] [PATCH SpectreV1+L1TF v7 2/9] x86/vioapic: block speculative out-of-bound accesses

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 21.02.19 at 09:16, <nmanthey@xxxxxxxxx> wrote:
> When interacting with io apic, a guest can specify values that are used
> as index to structures, and whose values are not compared against
> upper bounds to prevent speculative out-of-bound accesses. This change
> prevents these speculative accesses.
> 
> Furthermore, variables are initialized and the compiler is asked to not
> optimized these initializations, as the uninitialized variables might be
> used in a speculative out-of-bound access. Out of the four initialized
> variables, two are potentially problematic, namely ones in the functions
> vioapic_irq_positive_edge and vioapic_get_trigger_mode.
> 
> As the two problematic variables are both used in the common function
> gsi_vioapic, the mitigation is implemented there. As the access pattern
> of the currently non-guest-controlled functions might change in the
> future as well, the other variables are initialized as well.
> 
> This is part of the speculative hardening effort.
> 
> Signed-off-by: Norbert Manthey <nmanthey@xxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>



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