[stable:PATCH v5.4.184 19/22] KVM: arm64: Add templates for BHB mitigation sequences
James Morse
james.morse at arm.com
Tue Mar 15 11:24:12 PDT 2022
KVM writes the Spectre-v2 mitigation template at the beginning of each
vector when a CPU requires a specific sequence to run.
Because the template is copied, it can not be modified by the alternatives
at runtime.
Add templates for calling ARCH_WORKAROUND_3 and one for each value of K
in the brancy-loop. Instead of adding dummy functions for 'fn', which would
disable the Spectre-v2 mitigation, add template_start to indicate that a
template (and which one) is in use. Finally add a copy of
install_bp_hardening_cb() that is able to install these.
Signed-off-by: James Morse <james.morse at arm.com>
---
arch/arm64/include/asm/cpucaps.h | 3 +-
arch/arm64/include/asm/kvm_mmu.h | 6 ++-
arch/arm64/include/asm/mmu.h | 6 +++
arch/arm64/kernel/cpu_errata.c | 65 +++++++++++++++++++++++++++++++-
arch/arm64/kvm/hyp/hyp-entry.S | 54 ++++++++++++++++++++++++++
5 files changed, 130 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
index 1dc3c762fdcb..4ffa86149d28 100644
--- a/arch/arm64/include/asm/cpucaps.h
+++ b/arch/arm64/include/asm/cpucaps.h
@@ -55,7 +55,8 @@
#define ARM64_WORKAROUND_CAVIUM_TX2_219_TVM 45
#define ARM64_WORKAROUND_CAVIUM_TX2_219_PRFM 46
#define ARM64_WORKAROUND_1542419 47
+#define ARM64_SPECTRE_BHB 48
-#define ARM64_NCAPS 48
+#define ARM64_NCAPS 49
#endif /* __ASM_CPUCAPS_H */
diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index befe37d4bc0e..78d110667c0c 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -478,7 +478,8 @@ static inline void *kvm_get_hyp_vector(void)
void *vect = kern_hyp_va(kvm_ksym_ref(__kvm_hyp_vector));
int slot = -1;
- if (cpus_have_const_cap(ARM64_HARDEN_BRANCH_PREDICTOR) && data->fn) {
+ if ((cpus_have_const_cap(ARM64_HARDEN_BRANCH_PREDICTOR) ||
+ cpus_have_const_cap(ARM64_SPECTRE_BHB)) && data->template_start) {
vect = kern_hyp_va(kvm_ksym_ref(__bp_harden_hyp_vecs_start));
slot = data->hyp_vectors_slot;
}
@@ -507,7 +508,8 @@ static inline int kvm_map_vectors(void)
* !HBP + HEL2 -> allocate one vector slot and use exec mapping
* HBP + HEL2 -> use hardened vertors and use exec mapping
*/
- if (cpus_have_const_cap(ARM64_HARDEN_BRANCH_PREDICTOR)) {
+ if (cpus_have_const_cap(ARM64_HARDEN_BRANCH_PREDICTOR) ||
+ cpus_have_const_cap(ARM64_SPECTRE_BHB)) {
__kvm_bp_vect_base = kvm_ksym_ref(__bp_harden_hyp_vecs_start);
__kvm_bp_vect_base = kern_hyp_va(__kvm_bp_vect_base);
}
diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h
index 353450011e3d..1b9e49fb0e1b 100644
--- a/arch/arm64/include/asm/mmu.h
+++ b/arch/arm64/include/asm/mmu.h
@@ -82,6 +82,12 @@ typedef void (*bp_hardening_cb_t)(void);
struct bp_hardening_data {
int hyp_vectors_slot;
bp_hardening_cb_t fn;
+
+ /*
+ * template_start is only used by the BHB mitigation to identify the
+ * hyp_vectors_slot sequence.
+ */
+ const char *template_start;
};
#if (defined(CONFIG_HARDEN_BRANCH_PREDICTOR) || \
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index 182305000de3..30818b757d51 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -116,6 +116,14 @@ DEFINE_PER_CPU_READ_MOSTLY(struct bp_hardening_data, bp_hardening_data);
#ifdef CONFIG_KVM_INDIRECT_VECTORS
extern char __smccc_workaround_1_smc_start[];
extern char __smccc_workaround_1_smc_end[];
+extern char __smccc_workaround_3_smc_start[];
+extern char __smccc_workaround_3_smc_end[];
+extern char __spectre_bhb_loop_k8_start[];
+extern char __spectre_bhb_loop_k8_end[];
+extern char __spectre_bhb_loop_k24_start[];
+extern char __spectre_bhb_loop_k24_end[];
+extern char __spectre_bhb_loop_k32_start[];
+extern char __spectre_bhb_loop_k32_end[];
static void __copy_hyp_vect_bpi(int slot, const char *hyp_vecs_start,
const char *hyp_vecs_end)
@@ -129,11 +137,11 @@ static void __copy_hyp_vect_bpi(int slot, const char *hyp_vecs_start,
__flush_icache_range((uintptr_t)dst, (uintptr_t)dst + SZ_2K);
}
+static DEFINE_RAW_SPINLOCK(bp_lock);
static void install_bp_hardening_cb(bp_hardening_cb_t fn,
const char *hyp_vecs_start,
const char *hyp_vecs_end)
{
- static DEFINE_RAW_SPINLOCK(bp_lock);
int cpu, slot = -1;
/*
@@ -161,6 +169,7 @@ static void install_bp_hardening_cb(bp_hardening_cb_t fn,
__this_cpu_write(bp_hardening_data.hyp_vectors_slot, slot);
__this_cpu_write(bp_hardening_data.fn, fn);
+ __this_cpu_write(bp_hardening_data.template_start, hyp_vecs_start);
raw_spin_unlock(&bp_lock);
}
#else
@@ -1052,3 +1061,57 @@ enum mitigation_state arm64_get_spectre_bhb_state(void)
{
return spectre_bhb_state;
}
+
+#ifdef CONFIG_KVM_INDIRECT_VECTORS
+static const char *kvm_bhb_get_vecs_end(const char *start)
+{
+ if (start == __smccc_workaround_3_smc_start)
+ return __smccc_workaround_3_smc_end;
+ else if (start == __spectre_bhb_loop_k8_start)
+ return __spectre_bhb_loop_k8_end;
+ else if (start == __spectre_bhb_loop_k24_start)
+ return __spectre_bhb_loop_k24_end;
+ else if (start == __spectre_bhb_loop_k32_start)
+ return __spectre_bhb_loop_k32_end;
+
+ return NULL;
+}
+
+void kvm_setup_bhb_slot(const char *hyp_vecs_start)
+{
+ int cpu, slot = -1;
+ const char *hyp_vecs_end;
+
+ if (!IS_ENABLED(CONFIG_KVM) || !is_hyp_mode_available())
+ return;
+
+ hyp_vecs_end = kvm_bhb_get_vecs_end(hyp_vecs_start);
+ if (WARN_ON_ONCE(!hyp_vecs_start || !hyp_vecs_end))
+ return;
+
+ raw_spin_lock(&bp_lock);
+ for_each_possible_cpu(cpu) {
+ if (per_cpu(bp_hardening_data.template_start, cpu) == hyp_vecs_start) {
+ slot = per_cpu(bp_hardening_data.hyp_vectors_slot, cpu);
+ break;
+ }
+ }
+
+ if (slot == -1) {
+ slot = atomic_inc_return(&arm64_el2_vector_last_slot);
+ BUG_ON(slot >= BP_HARDEN_EL2_SLOTS);
+ __copy_hyp_vect_bpi(slot, hyp_vecs_start, hyp_vecs_end);
+ }
+
+ __this_cpu_write(bp_hardening_data.hyp_vectors_slot, slot);
+ __this_cpu_write(bp_hardening_data.template_start, hyp_vecs_start);
+ raw_spin_unlock(&bp_lock);
+}
+#else
+#define __smccc_workaround_3_smc_start NULL
+#define __spectre_bhb_loop_k8_start NULL
+#define __spectre_bhb_loop_k24_start NULL
+#define __spectre_bhb_loop_k32_start NULL
+
+void kvm_setup_bhb_slot(const char *hyp_vecs_start) { }
+#endif
diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S
index f36aad0f207b..2ad750208e33 100644
--- a/arch/arm64/kvm/hyp/hyp-entry.S
+++ b/arch/arm64/kvm/hyp/hyp-entry.S
@@ -347,4 +347,58 @@ ENTRY(__smccc_workaround_1_smc_start)
ldp x0, x1, [sp, #(8 * 2)]
add sp, sp, #(8 * 4)
ENTRY(__smccc_workaround_1_smc_end)
+
+ENTRY(__smccc_workaround_3_smc_start)
+ esb
+ sub sp, sp, #(8 * 4)
+ stp x2, x3, [sp, #(8 * 0)]
+ stp x0, x1, [sp, #(8 * 2)]
+ mov w0, #ARM_SMCCC_ARCH_WORKAROUND_3
+ smc #0
+ ldp x2, x3, [sp, #(8 * 0)]
+ ldp x0, x1, [sp, #(8 * 2)]
+ add sp, sp, #(8 * 4)
+ENTRY(__smccc_workaround_3_smc_end)
+
+ENTRY(__spectre_bhb_loop_k8_start)
+ esb
+ sub sp, sp, #(8 * 2)
+ stp x0, x1, [sp, #(8 * 0)]
+ mov x0, #8
+2: b . + 4
+ subs x0, x0, #1
+ b.ne 2b
+ dsb nsh
+ isb
+ ldp x0, x1, [sp, #(8 * 0)]
+ add sp, sp, #(8 * 2)
+ENTRY(__spectre_bhb_loop_k8_end)
+
+ENTRY(__spectre_bhb_loop_k24_start)
+ esb
+ sub sp, sp, #(8 * 2)
+ stp x0, x1, [sp, #(8 * 0)]
+ mov x0, #24
+2: b . + 4
+ subs x0, x0, #1
+ b.ne 2b
+ dsb nsh
+ isb
+ ldp x0, x1, [sp, #(8 * 0)]
+ add sp, sp, #(8 * 2)
+ENTRY(__spectre_bhb_loop_k24_end)
+
+ENTRY(__spectre_bhb_loop_k32_start)
+ esb
+ sub sp, sp, #(8 * 2)
+ stp x0, x1, [sp, #(8 * 0)]
+ mov x0, #32
+2: b . + 4
+ subs x0, x0, #1
+ b.ne 2b
+ dsb nsh
+ isb
+ ldp x0, x1, [sp, #(8 * 0)]
+ add sp, sp, #(8 * 2)
+ENTRY(__spectre_bhb_loop_k32_end)
#endif
--
2.30.2
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