[PATCH RFC v9 07/51] x86/sev: Add the host SEV-SNP initialization support

Michael Roth
2023-06-12T05:01:05Z

From: Brijesh Singh <brijesh.singh@amd.com>

The memory integrity guarantees of SEV-SNP are enforced through a new
structure called the Reverse Map Table (RMP). The RMP is a single data
structure shared across the system that contains one entry for every 4K
page of DRAM that may be used by SEV-SNP VMs. APM2 section 15.36 details
a number of steps needed to detect/enable SEV-SNP and RMP table support
on the host:

- Detect SEV-SNP support based on CPUID bit
- Initialize the RMP table memory reported by the RMP base/end MSR
registers and configure IOMMU to be compatible with RMP access
restrictions
- Set the MtrrFixDramModEn bit in SYSCFG MSR
- Set the SecureNestedPagingEn and VMPLEn bits in the SYSCFG MSR
- Configure IOMMU

RMP table entry format is non-architectural and it can vary by
processor. It is defined by the PPR. Restrict SNP support to CPU
models/families which are compatible with the current RMP table entry
format to guard against any undefined behavior when running on other
system types. Future models/support will handle this through an
architectural mechanism to allow for broader compatibility.

SNP host code depends on CONFIG_KVM_AMD_SEV config flag, which may be
enabled even when CONFIG_AMD_MEM_ENCRYPT isn't set, so update the
SNP-specific IOMMU helpers used here to rely on CONFIG_KVM_AMD_SEV
instead of CONFIG_AMD_MEM_ENCRYPT.

Co-developed-by: Ashish Kalra <ashish.kalra@amd.com>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
Co-developed-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
[mdr: rework commit message to be clearer about what patch does, squash
in early_rmptable_check() handling from Tom]
Signed-off-by: Michael Roth <michael.roth@amd.com>
---
arch/x86/coco/Makefile | 1 +
arch/x86/coco/sev/Makefile | 3 +
arch/x86/coco/sev/host.c | 212 +++++++++++++++++++++++
arch/x86/include/asm/disabled-features.h | 8 +-
arch/x86/include/asm/msr-index.h | 11 +-
arch/x86/include/asm/sev.h | 2 +
arch/x86/kernel/cpu/amd.c | 19 ++
drivers/iommu/amd/init.c | 2 +-
include/linux/amd-iommu.h | 2 +-
9 files changed, 256 insertions(+), 4 deletions(-)
create mode 100644 arch/x86/coco/sev/Makefile
create mode 100644 arch/x86/coco/sev/host.c

diff --git a/arch/x86/coco/Makefile b/arch/x86/coco/Makefile
index 6aa52e719bf5..6a7d876130e2 100644
--- a/arch/x86/coco/Makefile
+++ b/arch/x86/coco/Makefile
@@ -6,3 +6,4 @@ CFLAGS_core.o += -fno-stack-protector
obj-$(CONFIG_ARCH_HAS_CC_PLATFORM) += core.o

obj-$(CONFIG_INTEL_TDX_GUEST) += tdx/
+obj-$(CONFIG_KVM_AMD_SEV) += sev/
diff --git a/arch/x86/coco/sev/Makefile b/arch/x86/coco/sev/Makefile
new file mode 100644
index 000000000000..27c0500d75c8
--- /dev/null
+++ b/arch/x86/coco/sev/Makefile
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0
+
+obj-y += host.o
diff --git a/arch/x86/coco/sev/host.c b/arch/x86/coco/sev/host.c
new file mode 100644
index 000000000000..6907ce887b23
--- /dev/null
+++ b/arch/x86/coco/sev/host.c
@@ -0,0 +1,212 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * AMD SVM-SEV Host Support.
+ *
+ * Copyright (C) 2023 Advanced Micro Devices, Inc.
+ *
+ * Author: Ashish Kalra <ashish.kalra@amd.com>
+ *
+ */
+
+#include <linux/cc_platform.h>
+#include <linux/printk.h>
+#include <linux/mm_types.h>
+#include <linux/set_memory.h>
+#include <linux/memblock.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/cpumask.h>
+#include <linux/iommu.h>
+#include <linux/amd-iommu.h>
+
+#include <asm/sev.h>
+#include <asm/processor.h>
+#include <asm/setup.h>
+#include <asm/svm.h>
+#include <asm/smp.h>
+#include <asm/cpu.h>
+#include <asm/apic.h>
+#include <asm/cpuid.h>
+#include <asm/cmdline.h>
+#include <asm/iommu.h>
+
+/*
+ * The first 16KB from the RMP_BASE is used by the processor for the
+ * bookkeeping, the range needs to be added during the RMP entry lookup.
+ */
+#define RMPTABLE_CPU_BOOKKEEPING_SZ 0x4000
+
+static unsigned long rmptable_start __ro_after_init;
+static unsigned long rmptable_end __ro_after_init;
+
+#undef pr_fmt
+#define pr_fmt(fmt) "SEV-SNP: " fmt
+
+static int __mfd_enable(unsigned int cpu)
+{
+ u64 val;
+
+ if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
+ return 0;
+
+ rdmsrl(MSR_AMD64_SYSCFG, val);
+
+ val |= MSR_AMD64_SYSCFG_MFDM;
+
+ wrmsrl(MSR_AMD64_SYSCFG, val);
+
+ return 0;
+}
+
+static __init void mfd_enable(void *arg)
+{
+ __mfd_enable(smp_processor_id());
+}
+
+static int __snp_enable(unsigned int cpu)
+{
+ u64 val;
+
+ if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
+ return 0;
+
+ rdmsrl(MSR_AMD64_SYSCFG, val);
+
+ val |= MSR_AMD64_SYSCFG_SNP_EN;
+ val |= MSR_AMD64_SYSCFG_SNP_VMPL_EN;
+
+ wrmsrl(MSR_AMD64_SYSCFG, val);
+
+ return 0;
+}
+
+static __init void snp_enable(void *arg)
+{
+ __snp_enable(smp_processor_id());
+}
+
+bool snp_get_rmptable_info(u64 *start, u64 *len)
+{
+ u64 max_rmp_pfn, calc_rmp_sz, rmp_sz, rmp_base, rmp_end;
+
+ rdmsrl(MSR_AMD64_RMP_BASE, rmp_base);
+ rdmsrl(MSR_AMD64_RMP_END, rmp_end);
+
+ if (!rmp_base || !rmp_end) {
+ pr_err("Memory for the RMP table has not been reserved by BIOS\n");
+ return false;
+ }
+
+ rmp_sz = rmp_end - rmp_base + 1;
+
+ /*
+ * Calculate the amount the memory that must be reserved by the BIOS to
+ * address the whole RAM, including the bookkeeping area. The RMP itself
+ * must also be covered.
+ */
+ max_rmp_pfn = max_pfn;
+ if (PHYS_PFN(rmp_end) > max_pfn)
+ max_rmp_pfn = PHYS_PFN(rmp_end);
+
+ calc_rmp_sz = (max_rmp_pfn << 4) + RMPTABLE_CPU_BOOKKEEPING_SZ;
+
+ if (calc_rmp_sz > rmp_sz) {
+ pr_err("Memory reserved for the RMP table does not cover full system RAM (expected 0x%llx got 0x%llx)\n",
+ calc_rmp_sz, rmp_sz);
+ return false;
+ }
+
+ *start = rmp_base;
+ *len = rmp_sz;
+
+ return true;
+}
+
+static __init int __snp_rmptable_init(void)
+{
+ u64 rmp_base, sz;
+ void *start;
+ u64 val;
+
+ if (!snp_get_rmptable_info(&rmp_base, &sz))
+ return 1;
+
+ pr_info("RMP table physical address [0x%016llx - 0x%016llx]\n",
+ rmp_base, rmp_base + sz - 1);
+
+ start = memremap(rmp_base, sz, MEMREMAP_WB);
+ if (!start) {
+ pr_err("Failed to map RMP table addr 0x%llx size 0x%llx\n", rmp_base, sz);
+ return 1;
+ }
+
+ /*
+ * Check if SEV-SNP is already enabled, this can happen in case of
+ * kexec boot.
+ */
+ rdmsrl(MSR_AMD64_SYSCFG, val);
+ if (val & MSR_AMD64_SYSCFG_SNP_EN)
+ goto skip_enable;
+
+ /* Initialize the RMP table to zero */
+ memset(start, 0, sz);
+
+ /* Flush the caches to ensure that data is written before SNP is enabled. */
+ wbinvd_on_all_cpus();
+
+ /* MFDM must be enabled on all the CPUs prior to enabling SNP. */
+ on_each_cpu(mfd_enable, NULL, 1);
+
+ /* Enable SNP on all CPUs. */
+ on_each_cpu(snp_enable, NULL, 1);
+
+skip_enable:
+ rmptable_start = (unsigned long)start;
+ rmptable_end = rmptable_start + sz - 1;
+
+ return 0;
+}
+
+static int __init snp_rmptable_init(void)
+{
+ int family, model;
+
+ if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
+ return 0;
+
+ family = boot_cpu_data.x86;
+ model = boot_cpu_data.x86_model;
+
+ /*
+ * RMP table entry format is not architectural and it can vary by processor and
+ * is defined by the per-processor PPR. Restrict SNP support on the known CPU
+ * model and family for which the RMP table entry format is currently defined for.
+ */
+ if (!(family == 0x19 && model <= 0xaf) && !(family == 0x1a && model <= 0xf))
+ goto nosnp;
+
+ if (amd_iommu_snp_enable())
+ goto nosnp;
+
+ if (__snp_rmptable_init())
+ goto nosnp;
+
+ cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/rmptable_init:online", __snp_enable, NULL);
+
+ return 0;
+
+nosnp:
+ setup_clear_cpu_cap(X86_FEATURE_SEV_SNP);
+ return -ENOSYS;
+}
+
+/*
+ * This must be called after the PCI subsystem. This is because amd_iommu_snp_enable()
+ * is called to ensure the IOMMU supports the SEV-SNP feature, which can only be
+ * called after subsys_initcall().
+ *
+ * NOTE: IOMMU is enforced by SNP to ensure that hypervisor cannot program DMA
+ * directly into guest private memory. In case of SNP, the IOMMU ensures that
+ * the page(s) used for DMA are hypervisor owned.
+ */
+fs_initcall(snp_rmptable_init);
diff --git a/arch/x86/include/asm/disabled-features.h b/arch/x86/include/asm/disabled-features.h
index 5dfa4fb76f4b..0a9938aea305 100644
--- a/arch/x86/include/asm/disabled-features.h
+++ b/arch/x86/include/asm/disabled-features.h
@@ -99,6 +99,12 @@
# define DISABLE_TDX_GUEST (1 << (X86_FEATURE_TDX_GUEST & 31))
#endif

+#ifdef CONFIG_KVM_AMD_SEV
+# define DISABLE_SEV_SNP 0
+#else
+# define DISABLE_SEV_SNP (1 << (X86_FEATURE_SEV_SNP & 31))
+#endif
+
/*
* Make sure to add features to the correct mask
*/
@@ -123,7 +129,7 @@
DISABLE_ENQCMD)
#define DISABLED_MASK17 0
#define DISABLED_MASK18 0
-#define DISABLED_MASK19 0
+#define DISABLED_MASK19 (DISABLE_SEV_SNP)
#define DISABLED_MASK20 0
#define DISABLED_MASK_CHECK BUILD_BUG_ON_ZERO(NCAPINTS != 21)

diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index ad35355ee43e..db0f3a041930 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -574,6 +574,8 @@
#define MSR_AMD64_SEV_ENABLED BIT_ULL(MSR_AMD64_SEV_ENABLED_BIT)
#define MSR_AMD64_SEV_ES_ENABLED BIT_ULL(MSR_AMD64_SEV_ES_ENABLED_BIT)
#define MSR_AMD64_SEV_SNP_ENABLED BIT_ULL(MSR_AMD64_SEV_SNP_ENABLED_BIT)
+#define MSR_AMD64_RMP_BASE 0xc0010132
+#define MSR_AMD64_RMP_END 0xc0010133

/* SNP feature bits enabled by the hypervisor */
#define MSR_AMD64_SNP_VTOM BIT_ULL(3)
@@ -675,7 +677,14 @@
#define MSR_K8_TOP_MEM2 0xc001001d
#define MSR_AMD64_SYSCFG 0xc0010010
#define MSR_AMD64_SYSCFG_MEM_ENCRYPT_BIT 23
-#define MSR_AMD64_SYSCFG_MEM_ENCRYPT BIT_ULL(MSR_AMD64_SYSCFG_MEM_ENCRYPT_BIT)
+#define MSR_AMD64_SYSCFG_MEM_ENCRYPT BIT_ULL(MSR_AMD64_SYSCFG_MEM_ENCRYPT_BIT)
+#define MSR_AMD64_SYSCFG_SNP_EN_BIT 24
+#define MSR_AMD64_SYSCFG_SNP_EN BIT_ULL(MSR_AMD64_SYSCFG_SNP_EN_BIT)
+#define MSR_AMD64_SYSCFG_SNP_VMPL_EN_BIT 25
+#define MSR_AMD64_SYSCFG_SNP_VMPL_EN BIT_ULL(MSR_AMD64_SYSCFG_SNP_VMPL_EN_BIT)
+#define MSR_AMD64_SYSCFG_MFDM_BIT 19
+#define MSR_AMD64_SYSCFG_MFDM BIT_ULL(MSR_AMD64_SYSCFG_MFDM_BIT)
+
#define MSR_K8_INT_PENDING_MSG 0xc0010055
/* C1E active bits in int pending message */
#define K8_INTP_C1E_ACTIVE_MASK 0x18000000
diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index ebc271bb6d8e..d34c46db7dd1 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -197,6 +197,7 @@ void snp_set_wakeup_secondary_cpu(void);
bool snp_init(struct boot_params *bp);
void __init __noreturn snp_abort(void);
int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, unsigned long *fw_err);
+bool snp_get_rmptable_info(u64 *start, u64 *len);
#else
static inline void sev_es_ist_enter(struct pt_regs *regs) { }
static inline void sev_es_ist_exit(void) { }
@@ -221,6 +222,7 @@ static inline int snp_issue_guest_request(u64 exit_code, struct snp_req_data *in
{
return -ENOTTY;
}
+static inline bool snp_get_rmptable_info(u64 *start, u64 *len) { return false; }
#endif

#endif
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index a79774181f22..1493ddf89fdf 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -20,6 +20,7 @@
#include <asm/delay.h>
#include <asm/debugreg.h>
#include <asm/resctrl.h>
+#include <asm/sev.h>

#ifdef CONFIG_X86_64
# include <asm/mmconfig.h>
@@ -546,6 +547,20 @@ static void bsp_init_amd(struct cpuinfo_x86 *c)
resctrl_cpu_detect(c);
}

+static bool early_rmptable_check(void)
+{
+ u64 rmp_base, rmp_size;
+
+ /*
+ * For early BSP initialization, max_pfn won't be set up yet, wait until
+ * it is set before performing the RMP table calculations.
+ */
+ if (!max_pfn)
+ return true;
+
+ return snp_get_rmptable_info(&rmp_base, &rmp_size);
+}
+
static void early_detect_mem_encrypt(struct cpuinfo_x86 *c)
{
u64 msr;
@@ -587,6 +602,9 @@ static void early_detect_mem_encrypt(struct cpuinfo_x86 *c)
if (!(msr & MSR_K7_HWCR_SMMLOCK))
goto clear_sev;

+ if (cpu_has(c, X86_FEATURE_SEV_SNP) && !early_rmptable_check())
+ goto clear_snp;
+
return;

clear_all:
@@ -594,6 +612,7 @@ static void early_detect_mem_encrypt(struct cpuinfo_x86 *c)
clear_sev:
setup_clear_cpu_cap(X86_FEATURE_SEV);
setup_clear_cpu_cap(X86_FEATURE_SEV_ES);
+clear_snp:
setup_clear_cpu_cap(X86_FEATURE_SEV_SNP);
}
}
diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index 19a46b9f7357..33ea62d93540 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -3665,7 +3665,7 @@ int amd_iommu_pc_set_reg(struct amd_iommu *iommu, u8 bank, u8 cntr, u8 fxn, u64
return iommu_pc_get_set_reg(iommu, bank, cntr, fxn, value, true);
}

-#ifdef CONFIG_AMD_MEM_ENCRYPT
+#ifdef CONFIG_KVM_AMD_SEV
int amd_iommu_snp_enable(void)
{
/*
diff --git a/include/linux/amd-iommu.h b/include/linux/amd-iommu.h
index 953e6f12fa1c..8f0cde2d451c 100644
--- a/include/linux/amd-iommu.h
+++ b/include/linux/amd-iommu.h
@@ -206,7 +206,7 @@ int amd_iommu_pc_get_reg(struct amd_iommu *iommu, u8 bank, u8 cntr, u8 fxn,
u64 *value);
struct amd_iommu *get_amd_iommu(unsigned int idx);

-#ifdef CONFIG_AMD_MEM_ENCRYPT
+#ifdef CONFIG_KVM_AMD_SEV
int amd_iommu_snp_enable(void);
#endif

--
2.25.1