linux-kernel - [PATCH 2/2] x86/sev: let sev_es_efi_map

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Message-ID: <20250527144546.42981-2-kraxel@redhat.com>
Date: Tue, 27 May 2025 16:45:45 +0200
From: Gerd Hoffmann <kraxel@...hat.com>
To: Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Ard Biesheuvel <ardb@...nel.org>
Cc: kvm@...r.kernel.org,
	linux-coco@...ts.linux.dev,
	Gerd Hoffmann <kraxel@...hat.com>,
	linux-kernel@...r.kernel.org,
	linux-efi@...r.kernel.org
Subject: [PATCH 2/2] x86/sev: let sev_es_efi_map_ghcbs map the caa pages too

OVMF EFI firmware needs access to the CAA page to do SVSM protocol
calls.  So add that to sev_es_efi_map_ghcbs and also rename the function
to reflect the additional job it is doing now.

Signed-off-by: Gerd Hoffmann <kraxel@...hat.com>
---
 arch/x86/coco/sev/core.c       | 14 ++++++++++++--
 arch/x86/include/asm/sev.h     |  4 ++--
 arch/x86/platform/efi/efi_64.c |  2 +-
 3 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
index 145f594d7e6b..1cf2a8757ad6 100644
--- a/arch/x86/coco/sev/core.c
+++ b/arch/x86/coco/sev/core.c
@@ -1466,11 +1466,13 @@ int __init sev_es_setup_ap_jump_table(struct real_mode_header *rmh)
  * This is needed by the OVMF UEFI firmware which will use whatever it finds in
  * the GHCB MSR as its GHCB to talk to the hypervisor. So make sure the per-cpu
  * runtime GHCBs used by the kernel are also mapped in the EFI page-table.
+ *
+ * When running under SVSM the CCA page is needed too, so map it as well.
  */
-int __init sev_es_efi_map_ghcbs(pgd_t *pgd)
+int __init sev_es_efi_map_ghcbs_caas(pgd_t *pgd)
 {
 	struct sev_es_runtime_data *data;
-	unsigned long address, pflags;
+	unsigned long address, pflags, pflags_enc;
 	int cpu;
 	u64 pfn;
 
@@ -1478,6 +1480,7 @@ int __init sev_es_efi_map_ghcbs(pgd_t *pgd)
 		return 0;
 
 	pflags = _PAGE_NX | _PAGE_RW;
+	pflags_enc = cc_mkenc(pflags);
 
 	for_each_possible_cpu(cpu) {
 		data = per_cpu(runtime_data, cpu);
@@ -1487,6 +1490,13 @@ int __init sev_es_efi_map_ghcbs(pgd_t *pgd)
 
 		if (kernel_map_pages_in_pgd(pgd, pfn, address, 1, pflags))
 			return 1;
+
+		address = per_cpu(svsm_caa_pa, cpu);
+		if (address) {
+			pfn = address >> PAGE_SHIFT;
+			if (kernel_map_pages_in_pgd(pgd, pfn, address, 1, pflags_enc))
+				return 1;
+		}
 	}
 
 	return 0;
diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index ba7999f66abe..6b4f8b55e214 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -410,7 +410,7 @@ static __always_inline void sev_es_nmi_complete(void)
 	    cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT))
 		__sev_es_nmi_complete();
 }
-extern int __init sev_es_efi_map_ghcbs(pgd_t *pgd);
+extern int __init sev_es_efi_map_ghcbs_caas(pgd_t *pgd);
 extern void sev_enable(struct boot_params *bp);
 
 /*
@@ -491,7 +491,7 @@ static inline void sev_es_ist_enter(struct pt_regs *regs) { }
 static inline void sev_es_ist_exit(void) { }
 static inline int sev_es_setup_ap_jump_table(struct real_mode_header *rmh) { return 0; }
 static inline void sev_es_nmi_complete(void) { }
-static inline int sev_es_efi_map_ghcbs(pgd_t *pgd) { return 0; }
+static inline int sev_es_efi_map_ghcbs_caas(pgd_t *pgd) { return 0; }
 static inline void sev_enable(struct boot_params *bp) { }
 static inline int pvalidate(unsigned long vaddr, bool rmp_psize, bool validate) { return 0; }
 static inline int rmpadjust(unsigned long vaddr, bool rmp_psize, unsigned long attrs) { return 0; }
diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index a4b4ebd41b8f..1136c576831f 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -215,7 +215,7 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
 	 * When SEV-ES is active, the GHCB as set by the kernel will be used
 	 * by firmware. Create a 1:1 unencrypted mapping for each GHCB.
 	 */
-	if (sev_es_efi_map_ghcbs(pgd)) {
+	if (sev_es_efi_map_ghcbs_caas(pgd)) {
 		pr_err("Failed to create 1:1 mapping for the GHCBs!\n");
 		return 1;
 	}
-- 
2.49.0