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Re: [Xen-devel] [PATCH v5 0/4] x86: modify_ldt improvement, test, and config option

On 07/30/2015 01:06 PM, Andrew Cooper wrote:
On 30/07/15 17:31, Boris Ostrovsky wrote:
On 07/30/2015 12:12 PM, Andrew Cooper wrote:
On 30/07/15 17:05, Borislav Petkov wrote:
On Thu, Jul 30, 2015 at 11:53:34AM -0400, Boris Ostrovsky wrote:
As far as Xen guests are concerned,

Tested-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Does that mean, this patch 1/4 fixes the 32bit issue you guys are still
debugging on the v4 thread? Or does that need more fixing?

I was going to say... This v5 pre-dates figuring out what was wrong with
32bit Xen.  v5 1/4 is still susceptible.

Boris: does your Tested-by cover v5 + proposed fix?

Only V5, no extra changes.
Including running the ldt_gdt test?

Yes, except that 32-on-64 doesn't work, but that's not Xen-specific.

Still, user-visible behavior changes.

And perhaps dropping aliases in xen_alloc_ldt() may be sufficient
since with that done we will only have one mapping so a subsequent
fault will have "correct" cr2 provided by the hypervisor (from your
earlier email it sounded that hypervisor may have been providing
incorrect cr2 if alias exists)
They are sufficient to fix the first of the two bugs, but the free side
still has no protection against a missing l2, unless I am missing
something in the rest of the series?

Without aliases a subsequent fault *will* fill correct l2, won't it?


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