From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-dm3nam03on0088.outbound.protection.outlook.com ([104.47.41.88] helo=NAM03-DM3-obe.outbound.protection.outlook.com) by bombadil.infradead.org with esmtps (Exim 4.87 #1 (Red Hat Linux)) id 1dUwsV-0004N7-2Z for kexec@lists.infradead.org; Tue, 11 Jul 2017 15:15:08 +0000 Subject: Re: [PATCH v9 04/38] x86/CPU/AMD: Add the Secure Memory Encryption CPU feature References: <20170707133804.29711.1616.stgit@tlendack-t1.amdoffice.net> <20170707133850.29711.29549.stgit@tlendack-t1.amdoffice.net> <20170711055659.GA4554@nazgul.tnic> From: Tom Lendacky Message-ID: Date: Tue, 11 Jul 2017 10:14:34 -0500 MIME-Version: 1.0 In-Reply-To: <20170711055659.GA4554@nazgul.tnic> Content-Language: en-US List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Borislav Petkov , Brian Gerst Cc: linux-efi@vger.kernel.org, Brijesh Singh , Toshimitsu Kani , linux-doc@vger.kernel.org, Matt Fleming , the arch/x86 maintainers , Linux-MM , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , 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 7/11/2017 12:56 AM, Borislav Petkov wrote: > 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. I'll use this method for the change and avoid the #ifdefs. Thanks, Tom > > Thanks. > _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec