From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-by2nam01on0075.outbound.protection.outlook.com ([104.47.34.75] helo=NAM01-BY2-obe.outbound.protection.outlook.com) by bombadil.infradead.org with esmtps (Exim 4.87 #1 (Red Hat Linux)) id 1d1Fty-0001oL-1G for kexec@lists.infradead.org; Thu, 20 Apr 2017 17:29:56 +0000 Subject: Re: [PATCH v5 05/32] x86/CPU/AMD: Handle SME reduction in physical address size References: <20170418211612.10190.82788.stgit@tlendack-t1.amdoffice.net> <20170418211711.10190.30861.stgit@tlendack-t1.amdoffice.net> <20170420165922.j2inlwbchrs6senw@pd.tnic> From: Tom Lendacky Message-ID: Date: Thu, 20 Apr 2017 12:29:20 -0500 MIME-Version: 1.0 In-Reply-To: <20170420165922.j2inlwbchrs6senw@pd.tnic> 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 Cc: linux-efi@vger.kernel.org, Brijesh Singh , Toshimitsu Kani , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Matt Fleming , x86@kernel.org, linux-mm@kvack.org, Alexander Potapenko , "H. Peter Anvin" , Larry Woodman , linux-arch@vger.kernel.org, kvm@vger.kernel.org, Jonathan Corbet , Joerg Roedel , linux-doc@vger.kernel.org, kasan-dev@googlegroups.com, Ingo Molnar , Andrey Ryabinin , Dave Young , Rik van Riel , Arnd Bergmann , Konrad Rzeszutek Wilk , Andy Lutomirski , Thomas Gleixner , Dmitry Vyukov , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, "Michael S. Tsirkin" , Paolo Bonzini On 4/20/2017 11:59 AM, Borislav Petkov wrote: > On Tue, Apr 18, 2017 at 04:17:11PM -0500, Tom Lendacky wrote: >> When System Memory Encryption (SME) is enabled, the physical address >> space is reduced. Adjust the x86_phys_bits value to reflect this >> reduction. >> >> Signed-off-by: Tom Lendacky >> --- >> arch/x86/kernel/cpu/amd.c | 14 +++++++++++--- >> 1 file changed, 11 insertions(+), 3 deletions(-) > > ... > >> @@ -622,8 +624,14 @@ static void early_init_amd(struct cpuinfo_x86 *c) >> >> /* Check if SME is enabled */ >> rdmsrl(MSR_K8_SYSCFG, msr); >> - if (!(msr & MSR_K8_SYSCFG_MEM_ENCRYPT)) >> + if (msr & MSR_K8_SYSCFG_MEM_ENCRYPT) { >> + unsigned int ebx; >> + >> + ebx = cpuid_ebx(0x8000001f); >> + c->x86_phys_bits -= (ebx >> 6) & 0x3f; >> + } else { >> clear_cpu_cap(c, X86_FEATURE_SME); >> + } > > Lemme do some simplifying to save an indent level, get rid of local var > ebx and kill some { }-brackets for a bit better readability: > > if (c->extended_cpuid_level >= 0x8000001f) { > u64 msr; > > if (!cpu_has(c, X86_FEATURE_SME)) > return; > > /* Check if SME is enabled */ > rdmsrl(MSR_K8_SYSCFG, msr); > if (msr & MSR_K8_SYSCFG_MEM_ENCRYPT) > c->x86_phys_bits -= (cpuid_ebx(0x8000001f) >> 6) & 0x3f; > else > clear_cpu_cap(c, X86_FEATURE_SME); > } > Hmmm... and actually if cpu_has(X86_FEATURE_SME) is true then it's a given that extended_cpuid_level >= 0x8000001f. So this can be simplified to just: if (cpu_has(c, X86_FEATURE_SME)) { ... the rest of your suggestion (minus cpu_has()) ... } Thanks, Tom _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec