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Date: Fri, 20 Apr 2018 19:03:31 +0200
From: Borislav Petkov <bp@suse.de>
Subject: [MODERATED] Re: [patch 04/11] [PATCH v2 04/10] Linux Patch #4
Message-ID: <20180420170331.GL13977@pd.tnic>
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On Fri, Apr 20, 2018 at 12:39:40PM -0400, speck for Konrad Rzeszutek Wilk wro=
te:
> Wouldn't we leak our MD state to the guest? That is the guest
> may have cleared everything (svm->spec_ctrl is zero when we VMEXIT),
> and now we would be running it with MD bit set?

No, you pass the requested bits:

		x86_enable_ibrs(svm->spec_ctrl);

and that function then picks apart which bits the host supports and sets
them accordingly and filters out the reserved bits. You might call the
function then:

	x86_set_spec_ctrl();

and its counterpart

	x86_restore_spec_ctrl();

or whatever. The restore side would simply clear the IBRS bit as we
don't enable it on the host. It will restore the MD setting for the host
too.

--=20
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imend=C3=B6rffer, Jane Smithard, Graham Norton, HR=
B 21284 (AG N=C3=BCrnberg)
--=20