From: Michael Roth <michael.roth@amd.com>
Date: Thu, 24 Feb 2022 10:56:17 -0600
Subject: x86/compressed/64: Add identity mapping for Confidential Computing
 blob
Git-commit: 76f61e1e89b32f3e5d639f1b57413a919066da06
Patch-mainline: v5.19-rc1
References: jsc#SLE-19924, jsc#SLE-24814

The run-time kernel will need to access the Confidential Computing blob
very early during boot to access the CPUID table it points to. At that
stage, it will be relying on the identity-mapped page table set up by
the boot/compressed kernel, so make sure the blob and the CPUID table it
points to are mapped in advance.

  [ bp: Massage. ]

Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-38-brijesh.singh@amd.com

Acked-by: Joerg Roedel <jroedel@suse.de>
---
 arch/x86/boot/compressed/ident_map_64.c |    3 ++-
 arch/x86/boot/compressed/misc.h         |    2 ++
 arch/x86/boot/compressed/sev.c          |   21 +++++++++++++++++++++
 3 files changed, 25 insertions(+), 1 deletion(-)

--- a/arch/x86/boot/compressed/ident_map_64.c
+++ b/arch/x86/boot/compressed/ident_map_64.c
@@ -163,8 +163,9 @@ void initialize_identity_maps(void *rmod
 	cmdline = get_cmd_line_ptr();
 	kernel_add_identity_map(cmdline, cmdline + COMMAND_LINE_SIZE);
 
+	sev_prep_identity_maps(top_level_pgt);
+
 	/* Load the new page-table. */
-	sev_verify_cbit(top_level_pgt);
 	write_cr3(top_level_pgt);
 }
 
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -123,6 +123,7 @@ void sev_es_shutdown_ghcb(void);
 extern bool sev_es_check_ghcb_fault(unsigned long address);
 void snp_set_page_private(unsigned long paddr);
 void snp_set_page_shared(unsigned long paddr);
+void sev_prep_identity_maps(unsigned long top_level_pgt);
 #else
 static inline void sev_enable(struct boot_params *bp) { }
 static inline void sev_es_shutdown_ghcb(void) { }
@@ -132,6 +133,7 @@ static inline bool sev_es_check_ghcb_fau
 }
 static inline void snp_set_page_private(unsigned long paddr) { }
 static inline void snp_set_page_shared(unsigned long paddr) { }
+static inline void sev_prep_identity_maps(unsigned long top_level_pgt) { }
 #endif
 
 /* acpi.c */
--- a/arch/x86/boot/compressed/sev.c
+++ b/arch/x86/boot/compressed/sev.c
@@ -478,3 +478,24 @@ bool snp_init(struct boot_params *bp)
 
 	return true;
 }
+
+void sev_prep_identity_maps(unsigned long top_level_pgt)
+{
+	/*
+	 * 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.
+	 */
+	if (sev_snp_enabled()) {
+		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));
+
+		cc_info = (struct cc_blob_sev_info *)cc_info_pa;
+		kernel_add_identity_map(cc_info->cpuid_phys, cc_info->cpuid_phys + cc_info->cpuid_len);
+	}
+
+	sev_verify_cbit(top_level_pgt);
+}