From: Paolo Bonzini <pbonzini@redhat.com>
To: Richard Henderson <rth@twiddle.net>,
Eduardo Habkost <ehabkost@redhat.com>
Cc: Huaitong Han <huaitong.han@intel.com>,
qemu-devel@nongnu.org, kvm@vger.kernel.org
Subject: Re: [Qemu-devel] [for-2.6 PATCH 1/3] target-i386: Define structs for layout of xsave area
Date: Tue, 1 Dec 2015 18:27:17 +0100 [thread overview]
Message-ID: <565DD875.7090108@redhat.com> (raw)
In-Reply-To: <565DD6E9.1040906@twiddle.net>
On 01/12/2015 18:20, Richard Henderson wrote:
>>
>> X86XSaveArea will be used only when loading/saving state using
>> xsave, not for executing regular instructions.
>
> ... like the regular instruction xsave?
>
> https://patchwork.ozlabs.org/patch/493318/
Right, but that's a helper anyway.
>> In X86CPU, the
>> data is already stored as XMMReg unions (the one with the
>> XMM_[BWDQ] helpers).
>
> Of course. But those unions are arranged to be in big-endian format on
> big-endian hosts. So we need to swap the data back to little-endian
> format for storage into guest memory.
Yes, you can use byte moves with XMM_B (more obvious), or stq_le_p with
XMM_Q (faster I guess---though the compiler might optimize the former on
little-endian hosts). Either works with an uint8_t[] destination.
Paolo
next prev parent reply other threads:[~2015-12-01 17:27 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-28 19:56 [Qemu-devel] [for-2.6 PATCH 0/3] target-i386: Use C struct for xsave area layout, offsets & sizes Eduardo Habkost
2015-11-28 19:56 ` [Qemu-devel] [for-2.6 PATCH 1/3] target-i386: Define structs for layout of xsave area Eduardo Habkost
2015-11-30 11:18 ` Paolo Bonzini
2015-11-30 14:48 ` Eduardo Habkost
2015-12-01 17:09 ` Richard Henderson
2015-12-01 17:15 ` Eduardo Habkost
2015-12-01 17:20 ` Richard Henderson
2015-12-01 17:27 ` Paolo Bonzini [this message]
2015-12-01 18:34 ` Eduardo Habkost
2015-12-01 18:42 ` Richard Henderson
2015-11-28 19:56 ` [Qemu-devel] [for-2.6 PATCH 2/3] target-i386: Use xsave structs for ext_save_area Eduardo Habkost
2015-11-28 19:56 ` [Qemu-devel] [for-2.6 PATCH 3/3] target-i386: kvm: Use X86XSaveArea struct for xsave save/load Eduardo Habkost
2015-11-30 11:21 ` [Qemu-devel] [for-2.6 PATCH 0/3] target-i386: Use C struct for xsave area layout, offsets & sizes Paolo Bonzini
2015-11-30 14:14 ` Eduardo Habkost
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