From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f198.google.com (mail-wr0-f198.google.com [209.85.128.198]) by kanga.kvack.org (Postfix) with ESMTP id 27F636B04B2 for ; Tue, 11 Jul 2017 01:57:11 -0400 (EDT) Received: by mail-wr0-f198.google.com with SMTP id x23so29125192wrb.6 for ; Mon, 10 Jul 2017 22:57:11 -0700 (PDT) Received: from mail.skyhub.de (mail.skyhub.de. [5.9.137.197]) by mx.google.com with ESMTP id k4si8542359wmi.44.2017.07.10.22.57.09 for ; Mon, 10 Jul 2017 22:57:10 -0700 (PDT) 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-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Brian Gerst , Tom Lendacky Cc: linux-arch , linux-efi@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, the arch/x86 maintainers , kexec@lists.infradead.org, Linux Kernel Mailing List , kasan-dev@googlegroups.com, xen-devel@lists.xen.org, Linux-MM , iommu@lists.linux-foundation.org, Brijesh Singh , Toshimitsu Kani , Radim =?utf-8?B?S3LEjW3DocWZ?= , Matt Fleming , Alexander Potapenko , "H. Peter Anvin" , Larry Woodman , Jonathan Corbet , Joerg Roedel , "Michael S. Tsirkin" , Ingo Molnar , Andrey Ryabinin , Dave Young , Rik van Riel , Arnd Bergmann , Konrad Rzeszutek Wilk , Andy Lutomirski , Boris Ostrovsky , Dmitry Vyukov , Juergen Gross , 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. -- -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org