From: Dave Hansen <dave.hansen@linux.intel.com>
To: Yu-cheng Yu <yu-cheng.yu@intel.com>,
linux-kernel@vger.kernel.org, x86@kernel.org,
"H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>, Borislav Petkov <bp@suse.de>,
Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>,
"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
Fenghua Yu <fenghua.yu@intel.com>
Subject: Re: [PATCH v5 12/13] x86/xsaves: Fix fpstate_init() for XSAVES
Date: Mon, 9 May 2016 16:41:31 -0700 [thread overview]
Message-ID: <5731202B.2050805@linux.intel.com> (raw)
In-Reply-To: <9c6c58a0a4a66568b8e887944d2426d59370ae05.1462816638.git.yu-cheng.yu@intel.com>
On 05/09/2016 01:46 PM, Yu-cheng Yu wrote:
> When XSAVES is used, xsave.header.xcomp_bv[63] must be set.
So, that's not strictly correct. XSAVES can write to a completely empty
(0'd) memory buffer. It's only XRSTORS that _needs_ bit 63 set. The
instruction reference is pretty clear on this point.
Oh, and if you decided to do this for some reason, please have mercy and
go make a macro for 1<<63.
Also, I don't think the kernel ever checks for this bit. So are we
really calling XRSTORS on otherwise uninitialized xsave buffers?
next prev parent reply other threads:[~2016-05-09 23:41 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-09 20:45 [PATCH v5 00/12] x86/xsaves: Fix XSAVES issues Yu-cheng Yu
2016-05-09 20:45 ` [PATCH v5 01/13] x86/xsaves: Define and use user_xstate_size for xstate size in signal context Yu-cheng Yu
2016-05-10 11:04 ` Borislav Petkov
2016-05-10 15:59 ` Yu-cheng Yu
2016-05-10 16:29 ` Borislav Petkov
2016-05-10 16:30 ` Yu-cheng Yu
2016-05-09 20:45 ` [PATCH v5 02/13] x86/xsaves: Rename xstate_size to kernel_xstate_size to explicitly distinguish xstate size in kernel from user space Yu-cheng Yu
2016-05-10 17:01 ` Borislav Petkov
2016-05-10 17:08 ` Dave Hansen
2016-05-10 17:26 ` Borislav Petkov
2016-05-10 17:31 ` Dave Hansen
2016-05-09 20:46 ` [PATCH v5 03/13] x86/xsaves: Keep init_fpstate.xsave.header.xfeatures as zero for init optimization Yu-cheng Yu
2016-05-09 20:46 ` [PATCH v5 04/13] x86/xsaves: Introduce a new check that allows correct xstates copy from kernel to user directly Yu-cheng Yu
2016-05-09 22:09 ` Dave Hansen
2016-05-09 20:46 ` [PATCH v5 05/13] x86/xsaves: Align xstate components according to CPUID Yu-cheng Yu
2016-05-09 20:46 ` [PATCH v5 06/13] x86/xsaves: Supervisor state component offset Yu-cheng Yu
2016-05-09 20:46 ` [PATCH v5 07/13] x86/xsaves: Fix PTRACE frames for XSAVES Yu-cheng Yu
2016-05-09 20:46 ` [PATCH v5 08/13] x86/xsaves: Fix XSTATE component offset print out Yu-cheng Yu
2016-05-09 20:46 ` [PATCH v5 09/13] x86/xsaves: Fix xstate_offsets, xstate_sizes for non-extended states Yu-cheng Yu
2016-05-09 20:46 ` [PATCH v5 10/13] x86/xsaves: Fix __fpu_restore_sig() for XSAVES Yu-cheng Yu
2016-05-09 23:43 ` Dave Hansen
2016-05-09 20:46 ` [PATCH v5 11/13] x86/xsaves: Add WARN_ON_FPU() when a disabled xstate component offset is requested for a compacted format Yu-cheng Yu
2016-05-09 23:31 ` Dave Hansen
2016-05-09 23:44 ` Yu-cheng Yu
2016-05-09 23:54 ` Dave Hansen
2016-05-09 20:46 ` [PATCH v5 12/13] x86/xsaves: Fix fpstate_init() for XSAVES Yu-cheng Yu
2016-05-09 23:41 ` Dave Hansen [this message]
2016-05-09 23:50 ` Yu-cheng Yu
2016-05-10 0:01 ` Dave Hansen
2016-05-09 20:46 ` [PATCH v5 13/13] x86/xsaves: Re-enable XSAVES Yu-cheng Yu
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