[PATCH 5/5] x86/CPU/AMD: Track SNP host status with cc_platform_*()

Borislav Petkov
2024-03-27T15:44:29Z

From: "Borislav Petkov (AMD)" <bp@alien8.de>

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 rightfull place, while at it.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
arch/x86/include/asm/sev.h | 4 ++--
arch/x86/kernel/cpu/amd.c | 38 ++++++++++++++++++------------
arch/x86/kernel/cpu/mtrr/generic.c | 2 +-
arch/x86/kernel/sev.c | 10 --------
arch/x86/kvm/svm/sev.c | 2 +-
arch/x86/virt/svm/sev.c | 26 +++++++++++++-------
drivers/crypto/ccp/sev-dev.c | 2 +-
drivers/iommu/amd/init.c | 4 +++-
8 files changed, 49 insertions(+), 39 deletions(-)

diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index 9477b4053bce..780182cda3ab 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/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/sev.c b/arch/x86/kernel/sev.c
index b59b09c2f284..1e1a3c3bd1e8 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -2287,16 +2287,6 @@ 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/svm/sev.c b/arch/x86/kvm/svm/sev.c
index ae0ac12382b9..3d310b473e05 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/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);

/*
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 @@ 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();
+}
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 @@ 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;
}

--
2.43.0