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Fri, 18 Oct 2024 12:41:23 +0000 (UTC) Date: Fri, 18 Oct 2024 14:41:18 +0200 From: Borislav Petkov To: Tom Lendacky Cc: linux-kernel@vger.kernel.org, x86@kernel.org, Thomas Gleixner , Ingo Molnar , Dave Hansen , Michael Roth , Ashish Kalra Subject: Re: [PATCH v3 2/8] x86/sev: Add support for the RMPREAD instruction Message-ID: <20241018124118.GCZxJXbvAIcEak1gue@fat_crate.local> References: <4f9d9eac997784cd11f4243d545dd05e670b2e4c.1727709735.git.thomas.lendacky@amd.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <4f9d9eac997784cd11f4243d545dd05e670b2e4c.1727709735.git.thomas.lendacky@amd.com> On Mon, Sep 30, 2024 at 10:22:10AM -0500, Tom Lendacky wrote: > diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c > index 103a2dd6e81d..73d4f422829a 100644 > --- a/arch/x86/virt/svm/sev.c > +++ b/arch/x86/virt/svm/sev.c > @@ -301,6 +301,17 @@ static int get_rmpentry(u64 pfn, struct rmpentry *entry) > { > struct rmpentry_raw *e; > > + if (cpu_feature_enabled(X86_FEATURE_RMPREAD)) { > + int ret; > + > + asm volatile(".byte 0xf2, 0x0f, 0x01, 0xfd" > + : "=a" (ret) > + : "a" (pfn << PAGE_SHIFT), "c" (entry) > + : "memory", "cc"); > + > + return ret; > + } I think this should be: diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c index 73d9295dd013..5500c5d64cba 100644 --- a/arch/x86/virt/svm/sev.c +++ b/arch/x86/virt/svm/sev.c @@ -303,12 +303,11 @@ static int get_rmpentry(u64 pfn, struct rmpentry *entry) struct rmpentry_raw *e; if (cpu_feature_enabled(X86_FEATURE_RMPREAD)) { - int ret; + int ret = pfn << PAGE_SHIFT; asm volatile(".byte 0xf2, 0x0f, 0x01, 0xfd" - : "=a" (ret) - : "a" (pfn << PAGE_SHIFT), "c" (entry) - : "memory", "cc"); + : "+a" (ret), "+c" (entry) + :: "memory", "cc"); return ret; } because "The RCX register provides the effective address of a 16-byte data structure into which the RMP state is written." So your %rcx is both an input and an output operand and you need to do the "+" thing here too for that. Same for %rax. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette