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Date:   Sat, 23 Apr 2022 08:20:18 -0700
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Subject: Re: [patch 3/3] x86/fpu/xsave: Optimize XSAVEC/S when XGETBV1 is
 supported
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To:     Thomas Gleixner <tglx@linutronix.de>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        LKML <linux-kernel@vger.kernel.org>
Cc:     x86@kernel.org, Andrew Cooper <andrew.cooper3@citrix.com>,
        "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
References: <20220404103741.809025935@linutronix.de>
 <20220404104820.713066297@linutronix.de>
 <a93e6d3f-e8b9-2fab-1139-a8ba3dc4820b@intel.com> <87ee1t9oka.ffs@tglx>
 <878rs0vkd2.ffs@tglx> <60e5a4d1-df7c-d3bd-2730-e528cd75c351@amd.com>
 <87bkws6hmc.ffs@tglx>
From:   Dave Hansen <dave.hansen@intel.com>
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On 4/22/22 12:30, Thomas Gleixner wrote:
> So I just go and add the XSAVEC support alone as that's actually
> something which _is_ beneficial for guests.

Yeah, agreed.

When I went to test these patches, a bit loop with XSAVEC was ~10%
faster that XSAVEOPT.  This system has XSAVES, so wouldn't have been
using XSAVEOPT in the first place in the kernel.  But, this is at least
one more data point in favor of XSAVEC.