linux-kernel - [PATCH v2 09/14] virt: sev-guest: Choose the VMPCK key based on executing VMPL

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Message-ID: <a828ef42eb6af8789f4d1516693f950cea51d6c3.1709922929.git.thomas.lendacky@amd.com>
Date: Fri, 8 Mar 2024 12:35:24 -0600
From: Tom Lendacky <thomas.lendacky@....com>
To: <linux-kernel@...r.kernel.org>, <x86@...nel.org>
CC: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>, Andy Lutomirski <luto@...nel.org>, "Peter
 Zijlstra" <peterz@...radead.org>, Dan Williams <dan.j.williams@...el.com>,
	Michael Roth <michael.roth@....com>, Ashish Kalra <ashish.kalra@....com>
Subject: [PATCH v2 09/14] virt: sev-guest: Choose the VMPCK key based on executing VMPL

Currently, the sev-guest driver uses the vmpck-0 key by default. When an
SVSM is present the kernel is running at a VMPL other than 0 and the
vmpck-0 key is no longer available. So choose the vmpck key based on the
active VMPL level.

Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
---
 arch/x86/include/asm/sev.h              |  2 ++
 arch/x86/kernel/sev.c                   |  6 ++++++
 drivers/virt/coco/sev-guest/sev-guest.c | 10 +++++++---
 3 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index 1a07d86eb9d1..34bc84aee969 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -308,6 +308,7 @@ u64 sev_get_status(void);
 void kdump_sev_callback(void);
 void sev_show_status(void);
 void __init snp_remap_svsm_ca(void);
+int snp_get_vmpl(void);
 #else
 static inline void sev_es_ist_enter(struct pt_regs *regs) { }
 static inline void sev_es_ist_exit(void) { }
@@ -339,6 +340,7 @@ static inline u64 sev_get_status(void) { return 0; }
 static inline void kdump_sev_callback(void) { }
 static inline void sev_show_status(void) { }
 static inline void snp_remap_svsm_ca(void) { }
+static inline int snp_get_vmpl(void) { return 0; }
 #endif
 
 #ifdef CONFIG_KVM_AMD_SEV
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 807bd6ea8d85..8682af55802c 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -2466,6 +2466,12 @@ int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, struct sn
 }
 EXPORT_SYMBOL_GPL(snp_issue_guest_request);
 
+int snp_get_vmpl(void)
+{
+	return vmpl;
+}
+EXPORT_SYMBOL_GPL(snp_get_vmpl);
+
 static struct platform_device sev_guest_device = {
 	.name		= "sev-guest",
 	.id		= -1,
diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
index 87f241825bc3..1ff897913bf4 100644
--- a/drivers/virt/coco/sev-guest/sev-guest.c
+++ b/drivers/virt/coco/sev-guest/sev-guest.c
@@ -2,7 +2,7 @@
 /*
  * AMD Secure Encrypted Virtualization (SEV) guest driver interface
  *
- * Copyright (C) 2021 Advanced Micro Devices, Inc.
+ * Copyright (C) 2021-2024 Advanced Micro Devices, Inc.
  *
  * Author: Brijesh Singh <brijesh.singh@....com>
  */
@@ -70,8 +70,8 @@ struct snp_guest_dev {
 	u8 *vmpck;
 };
 
-static u32 vmpck_id;
-module_param(vmpck_id, uint, 0444);
+static int vmpck_id = -1;
+module_param(vmpck_id, int, 0444);
 MODULE_PARM_DESC(vmpck_id, "The VMPCK ID to use when communicating with the PSP.");
 
 /* Mutex to serialize the shared buffer access and command handling. */
@@ -923,6 +923,10 @@ static int __init sev_guest_probe(struct platform_device *pdev)
 	if (!snp_dev)
 		goto e_unmap;
 
+	/* Adjust the default VMPCK key based on the executing VMPL level */
+	if (vmpck_id == -1)
+		vmpck_id = snp_get_vmpl();
+
 	ret = -EINVAL;
 	snp_dev->vmpck = get_vmpck(vmpck_id, layout, &snp_dev->os_area_msg_seqno);
 	if (!snp_dev->vmpck) {
-- 
2.43.2