Re: [Xen-devel] [PATCH v2] x86: segment attribute handling adjustments

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 20/01/17 08:26, Jan Beulich wrote:
> Null selector loads into SS (possible in 64-bit mode only, and only in
> rings other than ring 3) must not alter SS.DPL. (This was found to be
> an issue on KVM, and fixed in Linux commit 33ab91103b.)
>
> Further arch_set_info_hvm_guest() didn't make sure that the ASSERT()s
> in hvm_set_segment_register() wouldn't trigger: Add further checks, but
> tolerate (adjust) clear accessed (CS, SS, DS, ES) and busy (TR) bits.
>
> Finally the setting of the accessed bits for user segments was lost by
> commit dd5c85e312 ("x86/hvm: Reposition the modification of raw segment
> data from the VMCB/VMCS"), yet VMX requires them to be set for usable
> segments. Add respective ASSERT()s (the only path not properly setting
> them was arch_set_info_hvm_guest()).
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

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