From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail.skyhub.de ([5.9.137.197]) by bombadil.infradead.org with esmtp (Exim 4.87 #1 (Red Hat Linux)) id 1dUoAy-0000YA-N5 for kexec@lists.infradead.org; Tue, 11 Jul 2017 05:57:39 +0000 Date: Tue, 11 Jul 2017 07:56:59 +0200 From: Borislav Petkov Subject: Re: [PATCH v9 04/38] x86/CPU/AMD: Add the Secure Memory Encryption CPU feature Message-ID: <20170711055659.GA4554@nazgul.tnic> References: <20170707133804.29711.1616.stgit@tlendack-t1.amdoffice.net> <20170707133850.29711.29549.stgit@tlendack-t1.amdoffice.net> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Brian Gerst , Tom Lendacky Cc: linux-efi@vger.kernel.org, Brijesh Singh , Toshimitsu Kani , linux-doc@vger.kernel.org, Matt Fleming , the arch/x86 maintainers , Linux-MM , Radim =?utf-8?B?S3LEjW3DocWZ?= , Alexander Potapenko , "H. Peter Anvin" , Larry Woodman , linux-arch , kvm@vger.kernel.org, Jonathan Corbet , Joerg Roedel , "Michael S. Tsirkin" , kasan-dev@googlegroups.com, Ingo Molnar , Andrey Ryabinin , Dave Young , Rik van Riel , Arnd Bergmann , Konrad Rzeszutek Wilk , Andy Lutomirski , Boris Ostrovsky , Dmitry Vyukov , Juergen Gross , kexec@lists.infradead.org, Linux Kernel Mailing List , xen-devel@lists.xen.org, iommu@lists.linux-foundation.org, Thomas Gleixner , Paolo Bonzini On Tue, Jul 11, 2017 at 01:07:46AM -0400, Brian Gerst wrote: > > If I make the scattered feature support conditional on CONFIG_X86_64 > > (based on comment below) then cpu_has() will always be false unless > > CONFIG_X86_64 is enabled. So this won't need to be wrapped by the > > #ifdef. > > If you change it to use cpu_feature_enabled(), gcc will see that it is > disabled and eliminate the dead code at compile time. Just do this: if (cpu_has(c, X86_FEATURE_SME)) { if (IS_ENABLED(CONFIG_X86_32)) { clear_cpu_cap(c, X86_FEATURE_SME); } else { u64 msr; /* Check if SME is enabled */ rdmsrl(MSR_K8_SYSCFG, msr); if (!(msr & MSR_K8_SYSCFG_MEM_ENCRYPT)) clear_cpu_cap(c, X86_FEATURE_SME); } } so that it is explicit that we disable it on 32-bit and we can save us the ifdeffery elsewhere. Thanks. -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. -- _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec