Re: [Xen-devel] [PATCH v5 2/7] x86/xpti: don't flush TLB twice when switching to 64-bit pv context

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 06/04/18 08:52, Juergen Gross wrote:
> When switching to a 64-bit pv context the TLB is flushed twice today:
> the first time when switching to the new address space in
> write_ptbase(), the second time when switching to guest mode in
> restore_to_guest.
>
> Limit the first flush to non-global entries in that case.
>
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

This isn't safe.  If any speculation/prefetching happens into the new
guest mappings, we will get machine check exceptions.

~Andrew

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