linux-kernel - Re: [CFT PATCH 0/2] KVM: support XSAVES usage in the host

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Message-ID: <547354B3.4070908@redhat.com>
Date:	Mon, 24 Nov 2014 16:54:27 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Nadav Amit <nadav.amit@...il.com>
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	kvm list <kvm@...r.kernel.org>,
	Nadav Amit <namit@...technion.ac.il>,
	Wanpeng Li <wanpeng.li@...ux.intel.com>
Subject: Re: [CFT PATCH 0/2] KVM: support XSAVES usage in the host



On 24/11/2014 16:28, Nadav Amit wrote:
> Since kvm_load_guest_fpu is called before the guest_fpu is ever stored, there are 2 more problems that currently cause #GP:
> 1. XCOMP_BV[63] = 0
> 2. XSTATE_BV sets a bit (including bit 63) that is not set in XCOMP_BV (XCOMP_BV is initialised to zero).
> 
> [see SDM 13.11 "OPERATION OF XRSTORS”]
> 
> Once I initialise XCOMP_BV to (1ull << 63) | XSTATE_BV, the guest runs successfully.
> I have not checked any other qemu functionality that might be affected by the patch.

Ah, so the problem is with KVM_SET_XSAVE.  Thanks!

Paolo
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