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

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Message-Id: <BEFBDB39-E273-45AF-AB9F-B80A41192FF6@gmail.com>
Date:	Mon, 24 Nov 2014 20:31:30 +0200
From:	Nadav Amit <nadav.amit@...il.com>
To:	Paolo Bonzini <pbonzini@...hat.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 Nov 24, 2014, at 19:53, Paolo Bonzini <pbonzini@...hat.com> wrote:
> 
> 
> 
> 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.
> 
> I posted patches that assume that QEMU calls KVM_SET_XSAVE early enough.
> If this is not the case, can you cook up and post a patch to
> kvm_arch_vcpu_init that fixes the remaining problem?

Sure. I will try to do so tomorrow.

Nadav

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