x86/CPU/AMD: Track SNP host status with cc_platform_*()

The host SNP worthiness can determined later, after alternatives have
been patched, in snp_rmptable_init() depending on cmdline options like
iommu=pt which is incompatible with SNP, for example.

Which means that one cannot use X86_FEATURE_SEV_SNP and will need to
have a special flag for that control.

Use that newly added CC_ATTR_HOST_SEV_SNP in the appropriate places.

Move kdump_sev_callback() to its rightful place, while at it.

Fixes: 216d106c ("x86/sev: Add SEV-SNP host initialization support")
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Tested-by: Srikanth Aithal <sraithal@amd.com>
Link: https://lore.kernel.org/r/20240327154317.29909-6-bp@alien8.de

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

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:

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);

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;

arch/x86/kvm/svm/sev.c

@@ -3174,7 +3174,7 @@ 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);
 
 	/*

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 @@ static int __init snp_rmptable_init(void)
 	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();
+}

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;

drivers/iommu/amd/init.c

@@ -3228,7 +3228,7 @@ static bool __init detect_ivrs(void)
 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;
 	}