linux-kernel - Re: [PATCH v2 2/2] x86/sev: let sev_es_efi_map

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250624130158.GIaFqhxjE8-lQqq7mt@fat_crate.local>
Date: Tue, 24 Jun 2025 15:01:58 +0200
From: Borislav Petkov <bp@...en8.de>
To: Gerd Hoffmann <kraxel@...hat.com>
Cc: linux-coco@...ts.linux.dev, kvm@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>, Ard Biesheuvel <ardb@...nel.org>,
	"open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <linux-kernel@...r.kernel.org>,
	"open list:EXTENSIBLE FIRMWARE INTERFACE (EFI)" <linux-efi@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] x86/sev: let sev_es_efi_map_ghcbs map the caa
 pages too

I got this now:

---
From: Gerd Hoffmann <kraxel@...hat.com>
Date: Mon, 2 Jun 2025 12:50:49 +0200
Subject: [PATCH] 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. For
example, when the SVSM implements an EFI variable store, such calls will be
necessary.

So add that to sev_es_efi_map_ghcbs() and also rename the function to reflect
the additional job it is doing now.

  [ bp: Massage. ]

Signed-off-by: Gerd Hoffmann <kraxel@...hat.com>
Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
Link: https://lore.kernel.org/20250602105050.1535272-3-kraxel@redhat.com
---
 arch/x86/coco/sev/core.c       | 15 +++++++++++++--
 arch/x86/include/asm/sev.h     |  4 ++--
 arch/x86/platform/efi/efi_64.c |  4 ++--
 3 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
index 8375ca7fbd8a..6af3e94ba0ee 100644
--- a/arch/x86/coco/sev/core.c
+++ b/arch/x86/coco/sev/core.c
@@ -1045,11 +1045,13 @@ 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)
 {
+	unsigned long address, pflags, pflags_enc;
 	struct sev_es_runtime_data *data;
-	unsigned long address, pflags;
 	int cpu;
 	u64 pfn;
 
@@ -1057,6 +1059,7 @@ 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);
@@ -1066,6 +1069,14 @@ 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)
+			return 1;
+
+		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 fbb616fcbfb8..5b809f0ef207 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -446,7 +446,7 @@ 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);
 
 /*
@@ -554,7 +554,7 @@ 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 e7e8f77f77f8..97e8032db45d 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -216,8 +216,8 @@ 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)) {
-		pr_err("Failed to create 1:1 mapping for the GHCBs!\n");
+	if (sev_es_efi_map_ghcbs_caas(pgd)) {
+		pr_err("Failed to create 1:1 mapping for the GHCBs and CAAs!\n");
 		return 1;
 	}
 
-- 
2.43.0


-- 
Regards/Gruss,
    Boris.

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