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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 , Cyrill Gorcunov , 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 , Weijiang Yang , "Kirill A . Shutemov" , John Allen , kcc@google.com, eranian@google.com, rppt@kernel.org, jamorris@linux.microsoft.com, dethoma@microsoft.com, akpm@linux-foundation.org, Andrew.Cooper3@citrix.com, christina.schimpe@intel.com, Yu-cheng Yu Subject: Re: [PATCH v4 04/39] x86/cpufeatures: Enable CET CR4 bit for shadow stack Message-ID: References: <20221203003606.6838-1-rick.p.edgecombe@intel.com> <20221203003606.6838-5-rick.p.edgecombe@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20221203003606.6838-5-rick.p.edgecombe@intel.com> X-Rspamd-Queue-Id: A91E2140002 X-Stat-Signature: k5k6frnjr5a6jh4x9bkofq4r5uxmsw6z X-Rspam-User: X-Spamd-Result: default: False [-4.70 / 9.00]; BAYES_HAM(-6.00)[99.99%]; SUSPICIOUS_RECIPS(1.50)[]; R_SPF_ALLOW(-0.20)[+a:mail.skyhub.de]; MIME_GOOD(-0.10)[text/plain]; RCVD_NO_TLS_LAST(0.10)[]; RCPT_COUNT_TWELVE(0.00)[39]; RCVD_VIA_SMTP_AUTH(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; MIME_TRACE(0.00)[0:+]; DMARC_DNSFAIL(0.00)[alien8.de : server fail]; DKIM_TRACE(0.00)[alien8.de:?]; ARC_SIGNED(0.00)[hostedemail.com:s=arc-20220608:i=1]; ARC_NA(0.00)[]; TO_MATCH_ENVRCPT_SOME(0.00)[]; FROM_HAS_DN(0.00)[]; TAGGED_RCPT(0.00)[]; TO_DN_SOME(0.00)[]; R_DKIM_TEMPFAIL(0.00)[alien8.de:s=dkim] X-Rspamd-Server: rspam08 X-HE-Tag: 1670417382-454861 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 Fri, Dec 02, 2022 at 04:35:31PM -0800, Rick Edgecombe wrote: > From: Yu-cheng Yu > > Setting CR4.CET is a prerequisite for utilizing any CET features, most of > which also require setting MSRs. ... > arch/x86/kernel/cpu/common.c | 37 ++++++++++++++++++++++++++++++------ > 1 file changed, 31 insertions(+), 6 deletions(-) Looks better. Let's get rid of the ifdeffery and simplify it even more. Diff ontop: --- diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 579f10222432..c364f3067121 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -597,12 +597,14 @@ __noendbr void ibt_restore(u64 save) #endif -#ifdef CONFIG_X86_CET static __always_inline void setup_cet(struct cpuinfo_x86 *c) { - bool kernel_ibt = HAS_KERNEL_IBT && cpu_feature_enabled(X86_FEATURE_IBT); - bool user_shstk; - u64 msr = 0; + bool kernel_ibt, user_shstk; + + if (!IS_ENABLED(CONFIG_X86_CET)) + return; + + kernel_ibt = HAS_KERNEL_IBT && cpu_feature_enabled(X86_FEATURE_IBT); /* * Enable user shadow stack only if the Linux defined user shadow stack @@ -618,21 +620,18 @@ static __always_inline void setup_cet(struct cpuinfo_x86 *c) set_cpu_cap(c, X86_FEATURE_USER_SHSTK); if (kernel_ibt) - msr = CET_ENDBR_EN; + wrmsrl(MSR_IA32_S_CET, CET_ENDBR_EN); + else + wrmsrl(MSR_IA32_S_CET, 0); - wrmsrl(MSR_IA32_S_CET, msr); cr4_set_bits(X86_CR4_CET); if (kernel_ibt && !ibt_selftest()) { pr_err("IBT selftest: Failed!\n"); wrmsrl(MSR_IA32_S_CET, 0); setup_clear_cpu_cap(X86_FEATURE_IBT); - return; } } -#else /* CONFIG_X86_CET */ -static inline void setup_cet(struct cpuinfo_x86 *c) {} -#endif __noendbr void cet_disable(void) { -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette