[PATCH v2 0/2] nosnp sev command line support

[PATCH v2 0/2] nosnp sev command line support

[Pavan Kumar Paluri]

Provide "nosnp" boot option via "sev=nosnp" kernel command line to
prevent SEV-SNP[1] capable host kernel from enabling SEV-SNP and
initializing Reverse Map Table (RMP) [1].

On providing sev=nosnp via kernel command line:
cat /sys/module/kvm_amd/parameters/sev_snp should be "N".

This patchset is based on tip/master.

Reference:
[1] https://www.amd.com/content/dam/amd/en/documents/processor-tech-docs/programmer-references/24593.pdf

Changelog:

v1->v2:
  * Pick R-b from Tom.
  * Include only those headers that provide the necessary definitions (Boris)
  * Provide appropriate references to SEV, SNP and RMP (Matthew)

---
Pavan Kumar Paluri (2):
  x86, KVM:SVM: Move sev specific parsing into arch/x86/virt/svm
  x86 KVM:SVM: Provide "nosnp" boot option for sev kernel command line

 .../arch/x86/x86_64/boot-options.rst          |  3 ++
 arch/x86/coco/sev/core.c                      | 44 -------------------
 arch/x86/include/asm/sev-common.h             | 30 +++++++++++++
 arch/x86/virt/svm/Makefile                    |  1 +
 arch/x86/virt/svm/cmdline.c                   | 39 ++++++++++++++++
 5 files changed, 73 insertions(+), 44 deletions(-)
 create mode 100644 arch/x86/virt/svm/cmdline.c


base-commit: a85536e1bce722cb184abbac98068217874bdd6e
-- 
2.34.1

[PATCH v2 1/2] x86, KVM:SVM: Move sev specific parsing into arch/x86/virt/svm

[Pavan Kumar Paluri]

Move SEV specific kernel command line option parsing support from
arch/x86/coco/sev/core.c to arch/x86/virt/svm/cmdline.c so that both
host and guest related SEV command line options can be supported.

No functional changes intended.

Signed-off-by: Pavan Kumar Paluri <papaluri@amd.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 arch/x86/coco/sev/core.c          | 44 -------------------------------
 arch/x86/include/asm/sev-common.h | 30 +++++++++++++++++++++
 arch/x86/virt/svm/Makefile        |  1 +
 arch/x86/virt/svm/cmdline.c       | 32 ++++++++++++++++++++++
 4 files changed, 63 insertions(+), 44 deletions(-)
 create mode 100644 arch/x86/virt/svm/cmdline.c

diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
index de1df0cb45da..ff19e805e7a1 100644
--- a/arch/x86/coco/sev/core.c
+++ b/arch/x86/coco/sev/core.c
@@ -141,33 +141,6 @@ static DEFINE_PER_CPU(struct sev_es_save_area *, sev_vmsa);
 static DEFINE_PER_CPU(struct svsm_ca *, svsm_caa);
 static DEFINE_PER_CPU(u64, svsm_caa_pa);
 
-struct sev_config {
-	__u64 debug		: 1,
-
-	      /*
-	       * Indicates when the per-CPU GHCB has been created and registered
-	       * and thus can be used by the BSP instead of the early boot GHCB.
-	       *
-	       * For APs, the per-CPU GHCB is created before they are started
-	       * and registered upon startup, so this flag can be used globally
-	       * for the BSP and APs.
-	       */
-	      ghcbs_initialized	: 1,
-
-	      /*
-	       * Indicates when the per-CPU SVSM CA is to be used instead of the
-	       * boot SVSM CA.
-	       *
-	       * For APs, the per-CPU SVSM CA is created as part of the AP
-	       * bringup, so this flag can be used globally for the BSP and APs.
-	       */
-	      use_cas		: 1,
-
-	      __reserved	: 61;
-};
-
-static struct sev_config sev_cfg __read_mostly;
-
 static __always_inline bool on_vc_stack(struct pt_regs *regs)
 {
 	unsigned long sp = regs->sp;
@@ -2374,23 +2347,6 @@ static int __init report_snp_info(void)
 }
 arch_initcall(report_snp_info);
 
-static int __init init_sev_config(char *str)
-{
-	char *s;
-
-	while ((s = strsep(&str, ","))) {
-		if (!strcmp(s, "debug")) {
-			sev_cfg.debug = true;
-			continue;
-		}
-
-		pr_info("SEV command-line option '%s' was not recognized\n", s);
-	}
-
-	return 1;
-}
-__setup("sev=", init_sev_config);
-
 static void update_attest_input(struct svsm_call *call, struct svsm_attest_call *input)
 {
 	/* If (new) lengths have been returned, propagate them up */
diff --git a/arch/x86/include/asm/sev-common.h b/arch/x86/include/asm/sev-common.h
index 98726c2b04f8..d3e7f97e2a4a 100644
--- a/arch/x86/include/asm/sev-common.h
+++ b/arch/x86/include/asm/sev-common.h
@@ -8,6 +8,9 @@
 #ifndef __ASM_X86_SEV_COMMON_H
 #define __ASM_X86_SEV_COMMON_H
 
+#include <asm/cache.h>
+#include <asm/pgtable_types.h>
+
 #define GHCB_MSR_INFO_POS		0
 #define GHCB_DATA_LOW			12
 #define GHCB_MSR_INFO_MASK		(BIT_ULL(GHCB_DATA_LOW) - 1)
@@ -220,4 +223,31 @@ struct snp_psc_desc {
 #define GHCB_ERR_INVALID_INPUT		5
 #define GHCB_ERR_INVALID_EVENT		6
 
+struct sev_config {
+	__u64 debug		: 1,
+
+	      /*
+	       * Indicates when the per-CPU GHCB has been created and registered
+	       * and thus can be used by the BSP instead of the early boot GHCB.
+	       *
+	       * For APs, the per-CPU GHCB is created before they are started
+	       * and registered upon startup, so this flag can be used globally
+	       * for the BSP and APs.
+	       */
+	      ghcbs_initialized	: 1,
+
+	      /*
+	       * Indicates when the per-CPU SVSM CA is to be used instead of the
+	       * boot SVSM CA.
+	       *
+	       * For APs, the per-CPU SVSM CA is created as part of the AP
+	       * bringup, so this flag can be used globally for the BSP and APs.
+	       */
+	      use_cas		: 1,
+
+	      __reserved	: 61;
+};
+
+extern struct sev_config sev_cfg __read_mostly;
+
 #endif
diff --git a/arch/x86/virt/svm/Makefile b/arch/x86/virt/svm/Makefile
index ef2a31bdcc70..eca6d71355fa 100644
--- a/arch/x86/virt/svm/Makefile
+++ b/arch/x86/virt/svm/Makefile
@@ -1,3 +1,4 @@
 # SPDX-License-Identifier: GPL-2.0
 
 obj-$(CONFIG_KVM_AMD_SEV) += sev.o
+obj-$(CONFIG_CPU_SUP_AMD) += cmdline.o
diff --git a/arch/x86/virt/svm/cmdline.c b/arch/x86/virt/svm/cmdline.c
new file mode 100644
index 000000000000..4fe34e831d8f
--- /dev/null
+++ b/arch/x86/virt/svm/cmdline.c
@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * AMD SVM-SEV command line parsing support
+ *
+ * Copyright (C) 2023 - 2024 Advanced Micro Devices, Inc.
+ *
+ * Author: Michael Roth <michael.roth@amd.com>
+ */
+
+#include <linux/string.h>
+#include <linux/printk.h>
+
+#include <asm/sev.h>
+
+struct sev_config sev_cfg;
+
+static int __init init_sev_config(char *str)
+{
+	char *s;
+
+	while ((s = strsep(&str, ","))) {
+		if (!strcmp(s, "debug")) {
+			sev_cfg.debug = true;
+			continue;
+		}
+
+		pr_info("SEV command-line option '%s' was not recognized\n", s);
+	}
+
+	return 1;
+}
+__setup("sev=", init_sev_config);
-- 
2.34.1

[PATCH v2 2/2] x86 KVM:SVM: Provide "nosnp" boot option for sev kernel command line

[Pavan Kumar Paluri]

Provide a "nosnp" kernel command line option to prevent enabling of the
RMP and SEV-SNP features in the host/hypervisor. Not initializing the
RMP removes system overhead associated with RMP checks.

Co-developed-by: Eric Van Tassell <Eric.VanTassell@amd.com>
Signed-off-by: Eric Van Tassell <Eric.VanTassell@amd.com>
Signed-off-by: Pavan Kumar Paluri <papaluri@amd.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 Documentation/arch/x86/x86_64/boot-options.rst | 3 +++
 arch/x86/virt/svm/cmdline.c                    | 7 +++++++
 2 files changed, 10 insertions(+)

diff --git a/Documentation/arch/x86/x86_64/boot-options.rst b/Documentation/arch/x86/x86_64/boot-options.rst
index 137432d34109..3d4e9a7dccf2 100644
--- a/Documentation/arch/x86/x86_64/boot-options.rst
+++ b/Documentation/arch/x86/x86_64/boot-options.rst
@@ -317,3 +317,6 @@ The available options are:
 
    debug
      Enable debug messages.
+
+   nosnp
+     Do not enable SEV-SNP (applies to host/hypervisor only).
diff --git a/arch/x86/virt/svm/cmdline.c b/arch/x86/virt/svm/cmdline.c
index 4fe34e831d8f..43039ec67606 100644
--- a/arch/x86/virt/svm/cmdline.c
+++ b/arch/x86/virt/svm/cmdline.c
@@ -10,6 +10,7 @@
 #include <linux/string.h>
 #include <linux/printk.h>
 
+#include <asm/cpufeature.h>
 #include <asm/sev.h>
 
 struct sev_config sev_cfg;
@@ -24,6 +25,12 @@ static int __init init_sev_config(char *str)
 			continue;
 		}
 
+		if (!strcmp(s, "nosnp")) {
+			setup_clear_cpu_cap(X86_FEATURE_SEV_SNP);
+			cc_platform_clear(CC_ATTR_HOST_SEV_SNP);
+			continue;
+		}
+
 		pr_info("SEV command-line option '%s' was not recognized\n", s);
 	}
 
-- 
2.34.1

Re: [PATCH v2 1/2] x86, KVM:SVM: Move sev specific parsing into arch/x86/virt/svm

[kernel test robot]

Hi Pavan,

kernel test robot noticed the following build warnings:

[auto build test WARNING on a85536e1bce722cb184abbac98068217874bdd6e]

url:    https://github.com/intel-lab-lkp/linux/commits/Pavan-Kumar-Paluri/x86-KVM-SVM-Move-sev-specific-parsing-into-arch-x86-virt-svm/20240903-083803
base:   a85536e1bce722cb184abbac98068217874bdd6e
patch link:    https://lore.kernel.org/r/20240903003511.1530454-2-papaluri%40amd.com
patch subject: [PATCH v2 1/2] x86, KVM:SVM: Move sev specific parsing into arch/x86/virt/svm
config: i386-buildonly-randconfig-001-20240903 (https://download.01.org/0day-ci/archive/20240903/202409031656.SS8NsjIN-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240903/202409031656.SS8NsjIN-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202409031656.SS8NsjIN-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from arch/x86/include/asm/sev.h:16,
                    from arch/x86/virt/svm/cmdline.c:13:
>> arch/x86/include/asm/coco.h:28:18: warning: 'cc_mask' defined but not used [-Wunused-const-variable=]
      28 | static const u64 cc_mask = 0;
         |                  ^~~~~~~


vim +/cc_mask +28 arch/x86/include/asm/coco.h

1c811d403afd73 Ard Biesheuvel     2024-02-03  22  
b577f542f93cbb Kirill A. Shutemov 2022-02-22  23  u64 cc_mkenc(u64 val);
b577f542f93cbb Kirill A. Shutemov 2022-02-22  24  u64 cc_mkdec(u64 val);
99485c4c026f02 Jason A. Donenfeld 2024-03-26  25  void cc_random_init(void);
b577f542f93cbb Kirill A. Shutemov 2022-02-22  26  #else
e4596477100706 Nathan Chancellor  2024-02-02  27  #define cc_vendor (CC_VENDOR_NONE)
a0a8d15a798be4 Kirill A. Shutemov 2024-04-24 @28  static const u64 cc_mask = 0;
e4596477100706 Nathan Chancellor  2024-02-02  29  

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH v2 1/2] x86, KVM:SVM: Move sev specific parsing into arch/x86/virt/svm

[Paluri, PavanKumar]

On 9/3/2024 3:44 AM, kernel test robot wrote:
> Hi Pavan,
> 
> kernel test robot noticed the following build warnings:
> 
> [auto build test WARNING on a85536e1bce722cb184abbac98068217874bdd6e]
> 
> url:    https://github.com/intel-lab-lkp/linux/commits/Pavan-Kumar-Paluri/x86-KVM-SVM-Move-sev-specific-parsing-into-arch-x86-virt-svm/20240903-083803
> base:   a85536e1bce722cb184abbac98068217874bdd6e
> patch link:    https://lore.kernel.org/r/20240903003511.1530454-2-papaluri%40amd.com
> patch subject: [PATCH v2 1/2] x86, KVM:SVM: Move sev specific parsing into arch/x86/virt/svm
> config: i386-buildonly-randconfig-001-20240903 (https://download.01.org/0day-ci/archive/20240903/202409031656.SS8NsjIN-lkp@intel.com/config)
> compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240903/202409031656.SS8NsjIN-lkp@intel.com/reproduce)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202409031656.SS8NsjIN-lkp@intel.com/
> 
> All warnings (new ones prefixed by >>):
> 
>    In file included from arch/x86/include/asm/sev.h:16,
>                     from arch/x86/virt/svm/cmdline.c:13:
>>> arch/x86/include/asm/coco.h:28:18: warning: 'cc_mask' defined but not used [-Wunused-const-variable=]
>       28 | static const u64 cc_mask = 0;
>          |                  ^~~~~~~
> 
> 
> vim +/cc_mask +28 arch/x86/include/asm/coco.h
> 
> 1c811d403afd73 Ard Biesheuvel     2024-02-03  22  
> b577f542f93cbb Kirill A. Shutemov 2022-02-22  23  u64 cc_mkenc(u64 val);
> b577f542f93cbb Kirill A. Shutemov 2022-02-22  24  u64 cc_mkdec(u64 val);
> 99485c4c026f02 Jason A. Donenfeld 2024-03-26  25  void cc_random_init(void);
> b577f542f93cbb Kirill A. Shutemov 2022-02-22  26  #else
> e4596477100706 Nathan Chancellor  2024-02-02  27  #define cc_vendor (CC_VENDOR_NONE)
> a0a8d15a798be4 Kirill A. Shutemov 2024-04-24 @28  static const u64 cc_mask = 0;
> e4596477100706 Nathan Chancellor  2024-02-02  29  
> 

The following diff resolves the build warning reported by kernel test robot.

diff --git a/arch/x86/virt/svm/cmdline.c b/arch/x86/virt/svm/cmdline.c
index 43039ec67606..9b900e950b4b 100644
--- a/arch/x86/virt/svm/cmdline.c
+++ b/arch/x86/virt/svm/cmdline.c
@@ -11,7 +11,7 @@
 #include <linux/printk.h>

 #include <asm/cpufeature.h>
-#include <asm/sev.h>
+#include <asm/sev-common.h>

 struct sev_config sev_cfg;

I will apply this fix to the patch and send a v3.

Thanks,
Pavan