Re: [PATCH v9 36/43] x86/compressed/64: Add identity mapping for Confidential Computing blob

From: Borislav Petkov <bp@alien8.de>
To: Brijesh Singh <brijesh.singh@amd.com>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
	kvm@vger.kernel.org, linux-efi@vger.kernel.org,
	platform-driver-x86@vger.kernel.org, linux-coco@lists.linux.dev,
	linux-mm@kvack.org, Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Joerg Roedel <jroedel@suse.de>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Ard Biesheuvel <ardb@kernel.org>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Sean Christopherson <seanjc@google.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Jim Mattson <jmattson@google.com>,
	Andy Lutomirski <luto@kernel.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Sergio Lopez <slp@redhat.com>, Peter Gonda <pgonda@google.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
	David Rientjes <rientjes@google.com>,
	Dov Murik <dovmurik@linux.ibm.com>,
	Tobin Feldman-Fitzthum <tobin@ibm.com>,
	Michael Roth <michael.roth@amd.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	"Kirill A . Shutemov" <kirill@shutemov.name>,
	Andi Kleen <ak@linux.intel.com>,
	"Dr . David Alan Gilbert" <dgilbert@redhat.com>,
	brijesh.ksingh@gmail.com, tony.luck@intel.com,
	marcorr@google.com, sathyanarayanan.kuppuswamy@linux.intel.com
Subject: Re: [PATCH v9 36/43] x86/compressed/64: Add identity mapping for Confidential Computing blob
Date: Sun, 6 Feb 2022 20:21:00 +0100	[thread overview]
Message-ID: <YgAfnGTiwtu2Fako@zn.tnic> (raw)
In-Reply-To: <20220128171804.569796-37-brijesh.singh@amd.com>

On Fri, Jan 28, 2022 at 11:17:57AM -0600, Brijesh Singh wrote:
> From: Michael Roth <michael.roth@amd.com>
> 
> The run-time kernel will need to access the Confidential Computing
> blob very early in boot to access the CPUID table it points to. At
> that stage of boot it will be relying on the identity-mapped page table
> set up by boot/compressed kernel, so make sure the blob and the CPUID
> table it points to are mapped in advance.
> 
> Signed-off-by: Michael Roth <michael.roth@amd.com>
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> ---
>  arch/x86/boot/compressed/ident_map_64.c |  3 ++-
>  arch/x86/boot/compressed/misc.h         |  2 ++
>  arch/x86/boot/compressed/sev.c          | 22 ++++++++++++++++++++++
>  3 files changed, 26 insertions(+), 1 deletion(-)

Do this ontop:

---

diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
index faf432684870..a5a9210d73b6 100644
--- a/arch/x86/boot/compressed/sev.c
+++ b/arch/x86/boot/compressed/sev.c
@@ -500,7 +500,7 @@ bool snp_init(struct boot_params *bp)
 void sev_prep_identity_maps(unsigned long top_level_pgt)
 {
 	/*
-	 * The ConfidentialComputing blob is used very early in uncompressed
+	 * The Confidential Computing blob is used very early in uncompressed
 	 * kernel to find the in-memory cpuid table to handle cpuid
 	 * instructions. Make sure an identity-mapping exists so it can be
 	 * accessed after switchover.
@@ -509,11 +509,10 @@ void sev_prep_identity_maps(unsigned long top_level_pgt)
 		unsigned long cc_info_pa = boot_params->cc_blob_address;
 		struct cc_blob_sev_info *cc_info;
 
-		kernel_add_identity_map(cc_info_pa,
-					cc_info_pa + sizeof(*cc_info));
+		kernel_add_identity_map(cc_info_pa, cc_info_pa + sizeof(*cc_info));
+
 		cc_info = (struct cc_blob_sev_info *)cc_info_pa;
-		kernel_add_identity_map((unsigned long)cc_info->cpuid_phys,
-					(unsigned long)cc_info->cpuid_phys + cc_info->cpuid_len);
+		kernel_add_identity_map(cc_info->cpuid_phys, cc_info->cpuid_phys + cc_info->cpuid_len);
 	}
 
 	sev_verify_cbit(top_level_pgt);

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette
