Re: [CFT PATCH v2 0/2] KVM: support XSAVES usage in the host

[Nadav Amit <nadav.amit@gmail.com>]

> On Nov 25, 2014, at 16:17, Paolo Bonzini <pbonzini@redhat.com> wrote:
> 
> 
> 
> On 25/11/2014 15:05, Nadav Amit wrote:
>>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>>> index 373b0ab9a32e..ca26681455c2 100644
>>> --- a/arch/x86/kvm/x86.c
>>> +++ b/arch/x86/kvm/x86.c
>>> @@ -6955,6 +6955,9 @@ int fx_init(struct kvm_vcpu *vcpu)
>>> 		return err;
>>> 
>>> 	fpu_finit(&vcpu->arch.guest_fpu);
>>> +	if (cpu_has_xsaves)
>>> +		vcpu->arch.guest_fpu.state->xsave.xsave_hdr.xcomp_bv =
>>> +			host_xcr0 | XSTATE_COMPACTION_ENABLED;
>>> 
>>> 	/*
>>> 	 * Ensure guest xcr0 is valid for loading
>> 
>> The second version works for me (w/qemu v2.1.0; Linux 3.13 guest). I
>> did not need to apply this patch on top. [although I am not sure whether
>> relying on userspace to call KVM_SET_XSAVE early enough is a good practice].
> 
> Did you actually try the patch? :)  If it works, I'm tempted to apply it
> anyway.
Yes, I tried it both with and without this patch.
Due to time constraints I only tested minimal functionality (Linux boot).
I will run more tests in the near future. Anyhow, you can put the:

Tested-by: Nadav Amit <namit@cs.technion.ac.il>

> 
>> One disclaimer: Since I got limited time with the machine, I executed
>> a slightly modified kernel/qemu, and not the latest version.
>> Anyhow, I don’t think these differences can have any impact.
> 
> Yes, that is no problem.

I am just worried that Wanpeng reported it fails, while I report it works...

Nadav