From: Tom Lendacky <thomas.lendacky@amd.com>
To: <linux-kernel@vger.kernel.org>, <x86@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Andy Lutomirski <luto@kernel.org>,
"Peter Zijlstra" <peterz@infradead.org>,
Dan Williams <dan.j.williams@intel.com>,
Michael Roth <michael.roth@amd.com>,
Ashish Kalra <ashish.kalra@amd.com>
Subject: [PATCH v2 03/14] x86/sev: Check for the presence of an SVSM in the SNP Secrets page
Date: Fri, 8 Mar 2024 12:35:18 -0600 [thread overview]
Message-ID: <bbd56ae7a73dac0436fa3af43c06ce3ac2d0c7fd.1709922929.git.thomas.lendacky@amd.com> (raw)
In-Reply-To: <cover.1709922929.git.thomas.lendacky@amd.com>
During early boot phases, check for the presence of an SVSM when running
as an SEV-SNP guest.
An SVSM is present if the 64-bit value at offset 0x148 into the secrets
page is non-zero. If an SVSM is present, save the SVSM Calling Area
address (CAA), located at offset 0x150 into the secrets page, and set
the VMPL level of the guest, which should be non-zero, to indicate the
presence of an SVSM.
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
arch/x86/boot/compressed/sev.c | 35 ++++++++---------
arch/x86/include/asm/sev-common.h | 4 ++
arch/x86/include/asm/sev.h | 25 +++++++++++-
arch/x86/kernel/sev-shared.c | 64 +++++++++++++++++++++++++++++++
arch/x86/kernel/sev.c | 16 ++++++++
5 files changed, 125 insertions(+), 19 deletions(-)
diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
index bd7222aad540..f54c0ceae1cb 100644
--- a/arch/x86/boot/compressed/sev.c
+++ b/arch/x86/boot/compressed/sev.c
@@ -12,6 +12,7 @@
*/
#include "misc.h"
+#include <linux/mm.h>
#include <asm/bootparam.h>
#include <asm/pgtable_types.h>
#include <asm/sev.h>
@@ -29,6 +30,15 @@
static struct ghcb boot_ghcb_page __aligned(PAGE_SIZE);
struct ghcb *boot_ghcb;
+/*
+ * SVSM related information:
+ * When running under an SVSM, the VMPL that Linux is executing at must be
+ * non-zero. The VMPL is therefore used to indicate the presence of an SVSM.
+ */
+static u8 vmpl __section(".data");
+static u64 boot_svsm_caa_pa __section(".data");
+static struct svsm_ca *boot_svsm_caa __section(".data");
+
/*
* Copy a version of this function here - insn-eval.c can't be used in
* pre-decompression code.
@@ -335,24 +345,6 @@ void do_boot_stage2_vc(struct pt_regs *regs, unsigned long exit_code)
sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_GEN_REQ);
}
-static bool running_at_vmpl0(void *va)
-{
- u64 attrs;
-
- /*
- * RMPADJUST modifies RMP permissions of a lesser-privileged (numerically
- * higher) privilege level. Here, clear the VMPL1 permission mask of the
- * GHCB page. If the guest is not running at VMPL0, this will fail.
- *
- * If the guest is running at VMPL0, it will succeed. Even if that operation
- * modifies permission bits, it is still ok to do so currently because Linux
- * SNP guests running at VMPL0 only run at VMPL0, so VMPL1 or higher
- * permission mask changes are a don't-care.
- */
- attrs = 1;
- return !rmpadjust((unsigned long)va, RMP_PG_SIZE_4K, attrs);
-}
-
/*
* SNP_FEATURES_IMPL_REQ is the mask of SNP features that will need
* guest side implementation for proper functioning of the guest. If any
@@ -480,6 +472,13 @@ static bool snp_setup(struct boot_params *bp)
*/
setup_cpuid_table(cc_info);
+ /*
+ * Record the SVSM Calling Area address (CAA) if the guest is not
+ * running at VMPL0. The CA will be used to communicate with the
+ * SVSM to perform the SVSM services.
+ */
+ setup_svsm_ca(cc_info);
+
/*
* Pass run-time kernel a pointer to CC info via boot_params so EFI
* config table doesn't need to be searched again during early startup
diff --git a/arch/x86/include/asm/sev-common.h b/arch/x86/include/asm/sev-common.h
index b463fcbd4b90..68a8cdf6fd6a 100644
--- a/arch/x86/include/asm/sev-common.h
+++ b/arch/x86/include/asm/sev-common.h
@@ -159,6 +159,10 @@ struct snp_psc_desc {
#define GHCB_TERM_NOT_VMPL0 3 /* SNP guest is not running at VMPL-0 */
#define GHCB_TERM_CPUID 4 /* CPUID-validation failure */
#define GHCB_TERM_CPUID_HV 5 /* CPUID failure during hypervisor fallback */
+#define GHCB_TERM_SECRETS_PAGE 6 /* Secrets page failure */
+#define GHCB_TERM_NO_SVSM 7 /* SVSM is not advertised in the secrets page */
+#define GHCB_TERM_SVSM_VMPL0 8 /* SVSM is present but has set VMPL to 0 */
+#define GHCB_TERM_SVSM_CAA 9 /* SVSM is present but the CA is not page aligned */
#define GHCB_RESP_CODE(v) ((v) & GHCB_MSR_INFO_MASK)
diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index 9477b4053bce..891e7d9a1f66 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -152,9 +152,32 @@ struct snp_secrets_page_layout {
u8 vmpck2[VMPCK_KEY_LEN];
u8 vmpck3[VMPCK_KEY_LEN];
struct secrets_os_area os_area;
- u8 rsvd3[3840];
+
+ u8 vmsa_tweak_bitmap[64];
+
+ /* SVSM fields */
+ u64 svsm_base;
+ u64 svsm_size;
+ u64 svsm_caa;
+ u32 svsm_max_version;
+ u8 svsm_guest_vmpl;
+ u8 rsvd3[3];
+
+ /* Remainder of page */
+ u8 rsvd4[3744];
} __packed;
+/*
+ * The SVSM Calling Area (CA) related structures.
+ */
+struct svsm_ca {
+ u8 call_pending;
+ u8 mem_available;
+ u8 rsvd1[6];
+
+ u8 svsm_buffer[PAGE_SIZE - 8];
+};
+
#ifdef CONFIG_AMD_MEM_ENCRYPT
extern void __sev_es_ist_enter(struct pt_regs *regs);
extern void __sev_es_ist_exit(void);
diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
index 8b04958da5e7..00bb808be44b 100644
--- a/arch/x86/kernel/sev-shared.c
+++ b/arch/x86/kernel/sev-shared.c
@@ -111,6 +111,24 @@ sev_es_terminate(unsigned int set, unsigned int reason)
asm volatile("hlt\n" : : : "memory");
}
+static bool running_at_vmpl0(void *va)
+{
+ u64 attrs;
+
+ /*
+ * RMPADJUST modifies RMP permissions of a lesser-privileged (numerically
+ * higher) privilege level. Here, clear the VMPL1 permission mask of the
+ * GHCB page. If the guest is not running at VMPL0, this will fail.
+ *
+ * If the guest is running at VMPL0, it will succeed. Even if that operation
+ * modifies permission bits, it is still ok to do so currently because Linux
+ * SNP guests running at VMPL0 only run at VMPL0, so VMPL1 or higher
+ * permission mask changes are a don't-care.
+ */
+ attrs = 1;
+ return !rmpadjust((unsigned long)va, RMP_PG_SIZE_4K, attrs);
+}
+
/*
* The hypervisor features are available from GHCB version 2 onward.
*/
@@ -1267,3 +1285,49 @@ static enum es_result vc_check_opcode_bytes(struct es_em_ctxt *ctxt,
return ES_UNSUPPORTED;
}
+
+/*
+ * Maintain the GPA of the SVSM Calling Area (CA) in order to utilize the SVSM
+ * services needed when not runnuing in VMPL0.
+ */
+static void __init setup_svsm_ca(const struct cc_blob_sev_info *cc_info)
+{
+ struct snp_secrets_page_layout *secrets_page;
+ u64 caa;
+
+ BUILD_BUG_ON(sizeof(*secrets_page) != PAGE_SIZE);
+
+ /*
+ * Use __pa() since this routine is running identity mapped when
+ * called, both by the decompressor code and the early kernel code.
+ */
+ if (running_at_vmpl0((void *)__pa(&boot_ghcb_page)))
+ return;
+
+ /*
+ * Not running at VMPL0, ensure everything has been properly supplied
+ * for running under an SVSM.
+ */
+ if (!cc_info || !cc_info->secrets_phys || cc_info->secrets_len != PAGE_SIZE)
+ sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_SECRETS_PAGE);
+
+ secrets_page = (struct snp_secrets_page_layout *)cc_info->secrets_phys;
+ if (!secrets_page->svsm_size)
+ sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_NO_SVSM);
+
+ if (!secrets_page->svsm_guest_vmpl)
+ sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_SVSM_VMPL0);
+
+ vmpl = secrets_page->svsm_guest_vmpl;
+
+ caa = secrets_page->svsm_caa;
+ if (!PAGE_ALIGNED(caa))
+ sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_SVSM_CAA);
+
+ /*
+ * The CA is identity mapped when this routine is called, both by the
+ * decompressor code and the early kernel code.
+ */
+ boot_svsm_caa = (struct svsm_ca *)caa;
+ boot_svsm_caa_pa = caa;
+}
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index b59b09c2f284..64799a04feb4 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -135,6 +135,15 @@ struct ghcb_state {
static DEFINE_PER_CPU(struct sev_es_runtime_data*, runtime_data);
static DEFINE_PER_CPU(struct sev_es_save_area *, sev_vmsa);
+/*
+ * SVSM related information:
+ * When running under an SVSM, the VMPL that Linux is executing at must be
+ * non-zero. The VMPL is therefore used to indicate the presence of an SVSM.
+ */
+static u8 vmpl __ro_after_init;
+static struct svsm_ca *boot_svsm_caa __ro_after_init;
+static u64 boot_svsm_caa_pa __ro_after_init;
+
struct sev_config {
__u64 debug : 1,
@@ -2122,6 +2131,13 @@ bool __head snp_init(struct boot_params *bp)
setup_cpuid_table(cc_info);
+ /*
+ * Record the SVSM Calling Area address (CAA) if the guest is not
+ * running at VMPL0. The CA will be used to communicate with the
+ * SVSM to perform the SVSM services.
+ */
+ setup_svsm_ca(cc_info);
+
/*
* The CC blob will be used later to access the secrets page. Cache
* it here like the boot kernel does.
--
2.43.2
next prev parent reply other threads:[~2024-03-08 18:36 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-08 18:35 [PATCH v2 00/14] Provide SEV-SNP support for running under an SVSM Tom Lendacky
2024-03-08 18:35 ` [PATCH v2 01/14] x86/sev: Rename snp_init() in the boot/compressed/sev.c file Tom Lendacky
2024-03-10 21:25 ` Borislav Petkov
2024-03-11 16:16 ` Tom Lendacky
2024-03-08 18:35 ` [PATCH v2 02/14] x86/sev: Make the VMPL0 checking function more generic Tom Lendacky
2024-03-08 18:35 ` Tom Lendacky [this message]
2024-03-09 0:33 ` [PATCH v2 03/14] x86/sev: Check for the presence of an SVSM in the SNP Secrets page Dionna Amalie Glaze
2024-03-11 14:50 ` Tom Lendacky
2024-03-08 18:35 ` [PATCH v2 04/14] x86/sev: Use kernel provided SVSM Calling Areas Tom Lendacky
2024-03-08 18:35 ` [PATCH v2 05/14] x86/sev: Perform PVALIDATE using the SVSM when not at VMPL0 Tom Lendacky
2024-03-08 18:35 ` [PATCH v2 06/14] x86/sev: Use the SVSM to create a vCPU when not in VMPL0 Tom Lendacky
2024-03-08 18:35 ` [PATCH v2 07/14] x86/sev: Provide SVSM discovery support Tom Lendacky
2024-03-08 18:35 ` [PATCH v2 08/14] x86/sev: Provide guest VMPL level to userspace Tom Lendacky
2024-03-08 18:35 ` [PATCH v2 09/14] virt: sev-guest: Choose the VMPCK key based on executing VMPL Tom Lendacky
2024-03-08 18:35 ` [PATCH v2 10/14] configfs-tsm: Allow the privlevel_floor attribute to be updated Tom Lendacky
2024-03-08 18:35 ` [PATCH v2 11/14] x86/sev: Extend the config-fs attestation support for an SVSM Tom Lendacky
2024-03-10 6:06 ` Kuppuswamy, Sathyanarayanan
2024-03-11 16:16 ` Tom Lendacky
2024-03-12 5:57 ` Kuppuswamy Sathyanarayanan
2024-03-12 13:29 ` Tom Lendacky
2024-03-08 18:35 ` [PATCH v2 12/14] fs/configfs: Add a callback to determine attribute visibility Tom Lendacky
2024-03-11 19:58 ` Tom Lendacky
2024-03-13 21:37 ` Joel Becker
2024-03-14 14:23 ` Tom Lendacky
2024-03-21 2:40 ` Dan Williams
2024-03-08 18:35 ` [PATCH v2 13/14] x86/sev: Hide SVSM attestation entries if not running under an SVSM Tom Lendacky
2024-03-23 17:24 ` Kuppuswamy, Sathyanarayanan
2024-03-25 14:05 ` Tom Lendacky
2024-03-26 1:10 ` Kuppuswamy Sathyanarayanan
2024-03-08 18:35 ` [PATCH v2 14/14] x86/sev: Allow non-VMPL0 execution when an SVSM is present Tom Lendacky
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