diff --git a/arch/x86/coco/core.c b/arch/x86/coco/core.c
index d07be9d05cd0..b31ef2424d19 100644
--- a/arch/x86/coco/core.c
+++ b/arch/x86/coco/core.c
@@ -3,19 +3,28 @@
  * Confidential Computing Platform Capability checks
  *
  * Copyright (C) 2021 Advanced Micro Devices, Inc.
+ * Copyright (C) 2024 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
  *
  * Author: Tom Lendacky <thomas.lendacky@amd.com>
  */
 
 #include <linux/export.h>
 #include <linux/cc_platform.h>
+#include <linux/string.h>
+#include <linux/random.h>
 
+#include <asm/archrandom.h>
 #include <asm/coco.h>
 #include <asm/processor.h>
 
 enum cc_vendor cc_vendor __ro_after_init = CC_VENDOR_NONE;
 u64 cc_mask __ro_after_init;
 
+static struct cc_attr_flags {
+	__u64 host_sev_snp	: 1,
+	      __resv		: 63;
+} cc_flags;
+
 static bool noinstr intel_cc_platform_has(enum cc_attr attr)
 {
 	switch (attr) {
@@ -89,6 +98,9 @@ static bool noinstr amd_cc_platform_has(enum cc_attr attr)
 	case CC_ATTR_GUEST_SEV_SNP:
 		return sev_status & MSR_AMD64_SEV_SNP_ENABLED;
 
+	case CC_ATTR_HOST_SEV_SNP:
+		return cc_flags.host_sev_snp;
+
 	default:
 		return false;
 	}
@@ -148,3 +160,84 @@ u64 cc_mkdec(u64 val)
 	}
 }
 EXPORT_SYMBOL_GPL(cc_mkdec);
+
+static void amd_cc_platform_clear(enum cc_attr attr)
+{
+	switch (attr) {
+	case CC_ATTR_HOST_SEV_SNP:
+		cc_flags.host_sev_snp = 0;
+		break;
+	default:
+		break;
+	}
+}
+
+void cc_platform_clear(enum cc_attr attr)
+{
+	switch (cc_vendor) {
+	case CC_VENDOR_AMD:
+		amd_cc_platform_clear(attr);
+		break;
+	default:
+		break;
+	}
+}
+
+static void amd_cc_platform_set(enum cc_attr attr)
+{
+	switch (attr) {
+	case CC_ATTR_HOST_SEV_SNP:
+		cc_flags.host_sev_snp = 1;
+		break;
+	default:
+		break;
+	}
+}
+
+void cc_platform_set(enum cc_attr attr)
+{
+	switch (cc_vendor) {
+	case CC_VENDOR_AMD:
+		amd_cc_platform_set(attr);
+		break;
+	default:
+		break;
+	}
+}
+
+__init void cc_random_init(void)
+{
+	/*
+	 * The seed is 32 bytes (in units of longs), which is 256 bits, which
+	 * is the security level that the RNG is targeting.
+	 */
+	unsigned long rng_seed[32 / sizeof(long)];
+	size_t i, longs;
+
+	if (!cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))
+		return;
+
+	/*
+	 * Since the CoCo threat model includes the host, the only reliable
+	 * source of entropy that can be neither observed nor manipulated is
+	 * RDRAND. Usually, RDRAND failure is considered tolerable, but since
+	 * CoCo guests have no other unobservable source of entropy, it's
+	 * important to at least ensure the RNG gets some initial random seeds.
+	 */
+	for (i = 0; i < ARRAY_SIZE(rng_seed); i += longs) {
+		longs = arch_get_random_longs(&rng_seed[i], ARRAY_SIZE(rng_seed) - i);
+
+		/*
+		 * A zero return value means that the guest doesn't have RDRAND
+		 * or the CPU is physically broken, and in both cases that
+		 * means most crypto inside of the CoCo instance will be
+		 * broken, defeating the purpose of CoCo in the first place. So
+		 * just panic here because it's absolutely unsafe to continue
+		 * executing.
+		 */
+		if (longs == 0)
+			panic("RDRAND is defective.");
+	}
+	add_device_randomness(rng_seed, sizeof(rng_seed));
+	memzero_explicit(rng_seed, sizeof(rng_seed));
+}
diff --git a/arch/x86/include/asm/coco.h b/arch/x86/include/asm/coco.h
index fb7388bbc212..c086699b0d0c 100644
--- a/arch/x86/include/asm/coco.h
+++ b/arch/x86/include/asm/coco.h
@@ -22,6 +22,7 @@ static inline void cc_set_mask(u64 mask)
 
 u64 cc_mkenc(u64 val);
 u64 cc_mkdec(u64 val);
+void cc_random_init(void);
 #else
 #define cc_vendor (CC_VENDOR_NONE)
 
@@ -34,6 +35,7 @@ static inline u64 cc_mkdec(u64 val)
 {
 	return val;
 }
+static inline void cc_random_init(void) { }
 #endif
 
 #endif /* _ASM_X86_COCO_H */
diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index 07e125f32528..7f57382afee4 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -228,7 +228,6 @@ int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, struct sn
 void snp_accept_memory(phys_addr_t start, phys_addr_t end);
 u64 snp_get_unsupported_features(u64 status);
 u64 sev_get_status(void);
-void kdump_sev_callback(void);
 void sev_show_status(void);
 #else
 static inline void sev_es_ist_enter(struct pt_regs *regs) { }
@@ -258,7 +257,6 @@ static inline int snp_issue_guest_request(u64 exit_code, struct snp_req_data *in
 static inline void snp_accept_memory(phys_addr_t start, phys_addr_t end) { }
 static inline u64 snp_get_unsupported_features(u64 status) { return 0; }
 static inline u64 sev_get_status(void) { return 0; }
-static inline void kdump_sev_callback(void) { }
 static inline void sev_show_status(void) { }
 #endif
 
@@ -270,6 +268,7 @@ int psmash(u64 pfn);
 int rmp_make_private(u64 pfn, u64 gpa, enum pg_level level, u32 asid, bool immutable);
 int rmp_make_shared(u64 pfn, enum pg_level level);
 void snp_leak_pages(u64 pfn, unsigned int npages);
+void kdump_sev_callback(void);
 #else
 static inline bool snp_probe_rmptable_info(void) { return false; }
 static inline int snp_lookup_rmpentry(u64 pfn, bool *assigned, int *level) { return -ENODEV; }
@@ -282,6 +281,7 @@ static inline int rmp_make_private(u64 pfn, u64 gpa, enum pg_level level, u32 as
 }
 static inline int rmp_make_shared(u64 pfn, enum pg_level level) { return -ENODEV; }
 static inline void snp_leak_pages(u64 pfn, unsigned int npages) {}
+static inline void kdump_sev_callback(void) { }
 #endif
 
 #endif
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 6d8677e80ddb..9bf17c9c29da 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -345,6 +345,28 @@ static void srat_detect_node(struct cpuinfo_x86 *c)
 #endif
 }
 
+static void bsp_determine_snp(struct cpuinfo_x86 *c)
+{
+#ifdef CONFIG_ARCH_HAS_CC_PLATFORM
+	cc_vendor = CC_VENDOR_AMD;
+
+	if (cpu_has(c, X86_FEATURE_SEV_SNP)) {
+		/*
+		 * RMP table entry format is not architectural and is defined by the
+		 * per-processor PPR. Restrict SNP support on the known CPU models
+		 * for which the RMP table entry format is currently defined for.
+		 */
+		if (!cpu_has(c, X86_FEATURE_HYPERVISOR) &&
+		    c->x86 >= 0x19 && snp_probe_rmptable_info()) {
+			cc_platform_set(CC_ATTR_HOST_SEV_SNP);
+		} else {
+			setup_clear_cpu_cap(X86_FEATURE_SEV_SNP);
+			cc_platform_clear(CC_ATTR_HOST_SEV_SNP);
+		}
+	}
+#endif
+}
+
 static void bsp_init_amd(struct cpuinfo_x86 *c)
 {
 	if (cpu_has(c, X86_FEATURE_CONSTANT_TSC)) {
@@ -452,21 +474,7 @@ static void bsp_init_amd(struct cpuinfo_x86 *c)
 		break;
 	}
 
-	if (cpu_has(c, X86_FEATURE_SEV_SNP)) {
-		/*
-		 * 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 (!boot_cpu_has(X86_FEATURE_ZEN3) &&
-		    !boot_cpu_has(X86_FEATURE_ZEN4) &&
-		    !boot_cpu_has(X86_FEATURE_ZEN5))
-			setup_clear_cpu_cap(X86_FEATURE_SEV_SNP);
-		else if (!snp_probe_rmptable_info())
-			setup_clear_cpu_cap(X86_FEATURE_SEV_SNP);
-	}
-
+	bsp_determine_snp(c);
 	return;
 
 warn:
diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index b5cc557cfc37..84d41be6d06b 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -2500,12 +2500,14 @@ static ssize_t set_bank(struct device *s, struct device_attribute *attr,
 		return -EINVAL;
 
 	b = &per_cpu(mce_banks_array, s->id)[bank];
-
 	if (!b->init)
 		return -ENODEV;
 
 	b->ctl = new;
+
+	mutex_lock(&mce_sysfs_mutex);
 	mce_restart();
+	mutex_unlock(&mce_sysfs_mutex);
 
 	return size;
 }
diff --git a/arch/x86/kernel/cpu/mtrr/generic.c b/arch/x86/kernel/cpu/mtrr/generic.c
index 422a4ddc2ab7..7b29ebda024f 100644
--- a/arch/x86/kernel/cpu/mtrr/generic.c
+++ b/arch/x86/kernel/cpu/mtrr/generic.c
@@ -108,7 +108,7 @@ static inline void k8_check_syscfg_dram_mod_en(void)
 	      (boot_cpu_data.x86 >= 0x0f)))
 		return;
 
-	if (cpu_feature_enabled(X86_FEATURE_SEV_SNP))
+	if (cc_platform_has(CC_ATTR_HOST_SEV_SNP))
 		return;
 
 	rdmsr(MSR_AMD64_SYSCFG, lo, hi);
diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index c99f26ebe7a6..1a8687f8073a 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -78,7 +78,8 @@ cpumask_any_housekeeping(const struct cpumask *mask, int exclude_cpu)
 	else
 		cpu = cpumask_any_but(mask, exclude_cpu);
 
-	if (!IS_ENABLED(CONFIG_NO_HZ_FULL))
+	/* Only continue if tick_nohz_full_mask has been initialized. */
+	if (!tick_nohz_full_enabled())
 		return cpu;
 
 	/* If the CPU picked isn't marked nohz_full nothing more needs doing. */
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 0109e6c510e0..e125e059e2c4 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -35,6 +35,7 @@
 #include <asm/bios_ebda.h>
 #include <asm/bugs.h>
 #include <asm/cacheinfo.h>
+#include <asm/coco.h>
 #include <asm/cpu.h>
 #include <asm/efi.h>
 #include <asm/gart.h>
@@ -991,6 +992,7 @@ void __init setup_arch(char **cmdline_p)
 	 * memory size.
 	 */
 	mem_encrypt_setup_arch();
+	cc_random_init();
 
 	efi_fake_memmap();
 	efi_find_mirror();
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 7e1e63cc48e6..38ad066179d8 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -2284,16 +2284,6 @@ static int __init snp_init_platform_device(void)
 }
 device_initcall(snp_init_platform_device);
 
-void kdump_sev_callback(void)
-{
-	/*
-	 * Do wbinvd() on remote CPUs when SNP is enabled in order to
-	 * safely do SNP_SHUTDOWN on the local CPU.
-	 */
-	if (cpu_feature_enabled(X86_FEATURE_SEV_SNP))
-		wbinvd();
-}
-
 void sev_show_status(void)
 {
 	int i;
diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index 3aaf7e86a859..0ebdd088f28b 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -122,6 +122,7 @@ config KVM_AMD_SEV
 	default y
 	depends on KVM_AMD && X86_64
 	depends on CRYPTO_DEV_SP_PSP && !(KVM_AMD=y && CRYPTO_DEV_CCP_DD=m)
+	select ARCH_HAS_CC_PLATFORM
 	help
 	  Provides support for launching Encrypted VMs (SEV) and Encrypted VMs
 	  with Encrypted State (SEV-ES) on AMD processors.
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index e5a4d9b0e79f..61a7531d41b0 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -3184,7 +3184,7 @@ struct page *snp_safe_alloc_page(struct kvm_vcpu *vcpu)
 	unsigned long pfn;
 	struct page *p;
 
-	if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
+	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
 		return alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);
 
 	/*
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index 0795b3464058..e674ccf720b9 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -229,6 +229,7 @@ SYM_CODE_END(srso_return_thunk)
 /* Dummy for the alternative in CALL_UNTRAIN_RET. */
 SYM_CODE_START(srso_alias_untrain_ret)
 	ANNOTATE_UNRET_SAFE
+	ANNOTATE_NOENDBR
 	ret
 	int3
 SYM_FUNC_END(srso_alias_untrain_ret)
diff --git a/arch/x86/mm/numa_32.c b/arch/x86/mm/numa_32.c
index 104544359d69..025fd7ea5d69 100644
--- a/arch/x86/mm/numa_32.c
+++ b/arch/x86/mm/numa_32.c
@@ -24,6 +24,7 @@
 
 #include <linux/memblock.h>
 #include <linux/init.h>
+#include <asm/pgtable_areas.h>
 
 #include "numa_internal.h"
 
diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
index cffe1157a90a..ab0e8448bb6e 100644
--- a/arch/x86/virt/svm/sev.c
+++ b/arch/x86/virt/svm/sev.c
@@ -77,7 +77,7 @@ static int __mfd_enable(unsigned int cpu)
 {
 	u64 val;
 
-	if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
+	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
 		return 0;
 
 	rdmsrl(MSR_AMD64_SYSCFG, val);
@@ -98,7 +98,7 @@ static int __snp_enable(unsigned int cpu)
 {
 	u64 val;
 
-	if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
+	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
 		return 0;
 
 	rdmsrl(MSR_AMD64_SYSCFG, val);
@@ -174,11 +174,11 @@ static int __init snp_rmptable_init(void)
 	u64 rmptable_size;
 	u64 val;
 
-	if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
+	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
 		return 0;
 
 	if (!amd_iommu_snp_en)
-		return 0;
+		goto nosnp;
 
 	if (!probed_rmp_size)
 		goto nosnp;
@@ -225,7 +225,7 @@ skip_enable:
 	return 0;
 
 nosnp:
-	setup_clear_cpu_cap(X86_FEATURE_SEV_SNP);
+	cc_platform_clear(CC_ATTR_HOST_SEV_SNP);
 	return -ENOSYS;
 }
 
@@ -246,7 +246,7 @@ static struct rmpentry *__snp_lookup_rmpentry(u64 pfn, int *level)
 {
 	struct rmpentry *large_entry, *entry;
 
-	if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
+	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
 		return ERR_PTR(-ENODEV);
 
 	entry = get_rmpentry(pfn);
@@ -363,7 +363,7 @@ int psmash(u64 pfn)
 	unsigned long paddr = pfn << PAGE_SHIFT;
 	int ret;
 
-	if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
+	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
 		return -ENODEV;
 
 	if (!pfn_valid(pfn))
@@ -472,7 +472,7 @@ static int rmpupdate(u64 pfn, struct rmp_state *state)
 	unsigned long paddr = pfn << PAGE_SHIFT;
 	int ret, level;
 
-	if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
+	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
 		return -ENODEV;
 
 	level = RMP_TO_PG_LEVEL(state->pagesize);
@@ -558,3 +558,13 @@ void snp_leak_pages(u64 pfn, unsigned int npages)
 	spin_unlock(&snp_leaked_pages_list_lock);
 }
 EXPORT_SYMBOL_GPL(snp_leak_pages);
+
+void kdump_sev_callback(void)
+{
+	/*
+	 * Do wbinvd() on remote CPUs when SNP is enabled in order to
+	 * safely do SNP_SHUTDOWN on the local CPU.
+	 */
+	if (cc_platform_has(CC_ATTR_HOST_SEV_SNP))
+		wbinvd();
+}
diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index f44efbb89c34..2102377f727b 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -1090,7 +1090,7 @@ static int __sev_snp_init_locked(int *error)
 	void *arg = &data;
 	int cmd, rc = 0;
 
-	if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
+	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
 		return -ENODEV;
 
 	sev = psp->sev_data;
diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index e7a44929f0da..33228c1c8980 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -3228,7 +3228,7 @@ out:
 static void iommu_snp_enable(void)
 {
 #ifdef CONFIG_KVM_AMD_SEV
-	if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
+	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
 		return;
 	/*
 	 * The SNP support requires that IOMMU must be enabled, and is
@@ -3236,12 +3236,14 @@ static void iommu_snp_enable(void)
 	 */
 	if (no_iommu || iommu_default_passthrough()) {
 		pr_err("SNP: IOMMU disabled or configured in passthrough mode, SNP cannot be supported.\n");
+		cc_platform_clear(CC_ATTR_HOST_SEV_SNP);
 		return;
 	}
 
 	amd_iommu_snp_en = check_feature(FEATURE_SNP);
 	if (!amd_iommu_snp_en) {
 		pr_err("SNP: IOMMU SNP feature not enabled, SNP cannot be supported.\n");
+		cc_platform_clear(CC_ATTR_HOST_SEV_SNP);
 		return;
 	}
 
diff --git a/include/linux/cc_platform.h b/include/linux/cc_platform.h
index cb0d6cd1c12f..60693a145894 100644
--- a/include/linux/cc_platform.h
+++ b/include/linux/cc_platform.h
@@ -90,6 +90,14 @@ enum cc_attr {
 	 * Examples include TDX Guest.
 	 */
 	CC_ATTR_HOTPLUG_DISABLED,
+
+	/**
+	 * @CC_ATTR_HOST_SEV_SNP: AMD SNP enabled on the host.
+	 *
+	 * The host kernel is running with the necessary features
+	 * enabled to run SEV-SNP guests.
+	 */
+	CC_ATTR_HOST_SEV_SNP,
 };
 
 #ifdef CONFIG_ARCH_HAS_CC_PLATFORM
@@ -107,10 +115,14 @@ enum cc_attr {
  * * FALSE - Specified Confidential Computing attribute is not active
  */
 bool cc_platform_has(enum cc_attr attr);
+void cc_platform_set(enum cc_attr attr);
+void cc_platform_clear(enum cc_attr attr);
 
 #else	/* !CONFIG_ARCH_HAS_CC_PLATFORM */
 
 static inline bool cc_platform_has(enum cc_attr attr) { return false; }
+static inline void cc_platform_set(enum cc_attr attr) { }
+static inline void cc_platform_clear(enum cc_attr attr) { }
 
 #endif	/* CONFIG_ARCH_HAS_CC_PLATFORM */