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Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Andy Lutomirski , Balbir Singh , Borislav Petkov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin , Weijiang Yang , Pengfei Xu Subject: Re: [PATCH v14 03/26] x86/fpu/xstate: Introduce CET MSR XSAVES supervisor states Message-ID: <20201012195808.GD14048@grain> References: <20201012153850.26996-1-yu-cheng.yu@intel.com> <20201012153850.26996-4-yu-cheng.yu@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201012153850.26996-4-yu-cheng.yu@intel.com> User-Agent: Mutt/1.14.6 (2020-07-11) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Oct 12, 2020 at 08:38:27AM -0700, Yu-cheng Yu wrote: ... > /* > * x86-64 Task Priority Register, CR8 > diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c > index 038e19c0019e..705fd9b94e31 100644 > --- a/arch/x86/kernel/fpu/xstate.c > +++ b/arch/x86/kernel/fpu/xstate.c > @@ -38,6 +38,9 @@ static const char *xfeature_names[] = > "Processor Trace (unused)" , > "Protection Keys User registers", > "unknown xstate feature" , > + "Control-flow User registers" , > + "Control-flow Kernel registers" , > + "unknown xstate feature" , > }; > > static short xsave_cpuid_features[] __initdata = { > @@ -51,6 +54,9 @@ static short xsave_cpuid_features[] __initdata = { > X86_FEATURE_AVX512F, > X86_FEATURE_INTEL_PT, > X86_FEATURE_PKU, > + -1, /* Unused */ > + X86_FEATURE_SHSTK, /* XFEATURE_CET_USER */ > + X86_FEATURE_SHSTK, /* XFEATURE_CET_KERNEL */ > }; Why do you need "-1" here in the array? The only 1:1 mapping is between the names itselves and values, not indices of arrays so i don't understand why we need this unused value. Sorry if it is a dumb questions and been discussed already.