From: Avi Kivity <avi@redhat.com>
To: Sheng Yang <sheng@linux.intel.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>,
kvm@vger.kernel.org, Dexuan Cui <dexuan.cui@intel.com>
Subject: Re: [PATCH v4] KVM: VMX: Enable XSAVE/XRSTORE for guest
Date: Mon, 24 May 2010 16:40:51 +0300 [thread overview]
Message-ID: <4BFA81E3.1020205@redhat.com> (raw)
In-Reply-To: <4BFA80CC.9070800@redhat.com>
On 05/24/2010 04:36 PM, Avi Kivity wrote:
>
> may be simplified if we move xcr0 reload back to guest entry (... :)
> but make it lazy:
>
> save_host_state: nothing
> set cr4.osxsave: nothing
> clear cr4.osxsave: nothing
> guest entry: if (gcr4.osxsave && !guest_xcr0_loaded) {
> guest_xcr0_loaded = true, load gxcr0 }
> load_host_state: if (guest_xcr0_loaded) { guest_xcr0_loaded = false;
> load host xcr0 }
> fpu switching: if (guest_xcr0_loaded) { guest_xcr0_loaded = false;
> load host xcr0 }, do fpu stuff
>
> So we delay xcr0 reload as late as possible for both entry and exit.
>
btw, this is similar to how we switch the fpu itself:
if-needed-and-not-already-loaded on guest entry, if-loaded on vcpu_put.
--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.
next prev parent reply other threads:[~2010-05-24 13:41 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-24 10:03 [PATCH v4] KVM: VMX: Enable XSAVE/XRSTORE for guest Sheng Yang
2010-05-24 13:36 ` Avi Kivity
2010-05-24 13:40 ` Avi Kivity [this message]
2010-05-25 6:28 ` Sheng Yang
2010-05-25 7:14 ` Avi Kivity
2010-05-24 13:47 ` Avi Kivity
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