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Shutemov" To: Borislav Petkov Cc: Tom Lendacky , linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org, iommu@lists.linux-foundation.org, kvm@vger.kernel.org, linux-efi@vger.kernel.org, platform-driver-x86@vger.kernel.org, linux-graphics-maintainer@vmware.com, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org, Brijesh Singh , Joerg Roedel , Andi Kleen , Sathyanarayanan Kuppuswamy , Tianyu Lan , Christoph Hellwig , Thomas Gleixner , Ingo Molnar , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Will Deacon Subject: Re: [PATCH v3 5/8] x86/sme: Replace occurrences of sme_active() with cc_platform_has() Message-ID: <20210924094132.gxyqp4z3qdk5w4j6@box.shutemov.name> References: <20210921212059.wwlytlmxoft4cdth@box.shutemov.name> <20210921213401.i2pzaotgjvn4efgg@box.shutemov.name> <00f52bf8-cbc6-3721-f40e-2f51744751b0@amd.com> <20210921215830.vqxd75r4eyau6cxy@box.shutemov.name> <01891f59-7ec3-cf62-a8fc-79f79ca76587@amd.com> <20210922143015.vvxvh6ec73lffvkf@box.shutemov.name> <20210922210558.itofvu3725dap5xx@box.shutemov.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 23, 2021 at 08:21:03PM +0200, Borislav Petkov wrote: > On Thu, Sep 23, 2021 at 12:05:58AM +0300, Kirill A. Shutemov wrote: > > Unless we find other way to guarantee RIP-relative access, we must use > > fixup_pointer() to access any global variables. > > Yah, I've asked compiler folks about any guarantees we have wrt > rip-relative addresses but it doesn't look good. Worst case, we'd have > to do the fixup_pointer() thing. > > In the meantime, Tom and I did some more poking at this and here's a > diff ontop. > > The direction being that we'll stick both the AMD and Intel > *cc_platform_has() call into cc_platform.c for which instrumentation > will be disabled so no issues with that. > > And that will keep all that querying all together in a single file. And still do cc_platform_has() calls in __startup_64() codepath? It's broken. Intel detection in cc_platform_has() relies on boot_cpu_data.x86_vendor which is not initialized until early_cpu_init() in setup_arch(). Given that X86_VENDOR_INTEL is 0 it leads to false-positive. I think opencode these two calls is the way forward. Maybe also move the check from sme_encrypt_kernel() to __startup_64(). -- Kirill A. Shutemov