KVM: arm64: Allow indirect vectors to be used without SPECTRE_V3A

commit 5bdf3437603d4af87f9c7f424b0c8aeed2420745 upstream.

CPUs vulnerable to Spectre-BHB either need to make an SMC-CC firmware
call from the vectors, or run a sequence of branches. This gets added
to the hyp vectors. If there is no support for arch-workaround-1 in
firmware, the indirect vector will be used.

kvm_init_vector_slots() only initialises the two indirect slots if
the platform is vulnerable to Spectre-v3a. pKVM's hyp_map_vectors()
only initialises __hyp_bp_vect_base if the platform is vulnerable to
Spectre-v3a.

As there are about to more users of the indirect vectors, ensure
their entries in hyp_spectre_vector_selector[] are always initialised,
and __hyp_bp_vect_base defaults to the regular VA mapping.

The Spectre-v3a check is moved to a helper
kvm_system_needs_idmapped_vectors(), and merged with the code
that creates the hyp mappings.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

4 files changed, 16 insertions, 2 deletions

diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
index e7d98997c09c..f42fd0a2e81c 100644
--- a/arch/arm64/include/asm/cpucaps.h
+++ b/arch/arm64/include/asm/cpucaps.h
@@ -66,7 +66,8 @@
 #define ARM64_HAS_TLB_RANGE			56
 #define ARM64_MTE				57
 #define ARM64_WORKAROUND_1508412		58
+#define ARM64_SPECTRE_BHB			59
 
-#define ARM64_NCAPS				59
+#define ARM64_NCAPS				60
 
 #endif /* __ASM_CPUCAPS_H */
diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
index 044bb9e2cd74..c34cd44637d2 100644
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -35,6 +35,8 @@
 #define KVM_VECTOR_PREAMBLE	(2 * AARCH64_INSN_SIZE)
 
 #define __SMCCC_WORKAROUND_1_SMC_SZ 36
+#define __SMCCC_WORKAROUND_3_SMC_SZ 36
+#define __SPECTRE_BHB_LOOP_SZ       44
 
 #define KVM_HOST_SMCCC_ID(id)						\
 	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,				\
@@ -199,6 +201,10 @@ extern void __vgic_v3_init_lrs(void);
 extern u32 __kvm_get_mdcr_el2(void);
 
 extern char __smccc_workaround_1_smc[__SMCCC_WORKAROUND_1_SMC_SZ];
+extern char __smccc_workaround_3_smc[__SMCCC_WORKAROUND_3_SMC_SZ];
+extern char __spectre_bhb_loop_k8[__SPECTRE_BHB_LOOP_SZ];
+extern char __spectre_bhb_loop_k24[__SPECTRE_BHB_LOOP_SZ];
+extern char __spectre_bhb_loop_k32[__SPECTRE_BHB_LOOP_SZ];
 
 /*
  * Obtain the PC-relative address of a kernel symbol
diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index 331394306cce..47dafd6ab3a3 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -237,7 +237,8 @@ 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_SPECTRE_V2) && data->fn) {
+	if ((cpus_have_const_cap(ARM64_SPECTRE_V2) ||
+	     cpus_have_const_cap(ARM64_SPECTRE_BHB)) && data->template_start) {
 		vect = kern_hyp_va(kvm_ksym_ref(__bp_harden_hyp_vecs));
 		slot = data->hyp_vectors_slot;
 	}
diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h
index c7315862e243..bc151b7dc042 100644
--- a/arch/arm64/include/asm/mmu.h
+++ b/arch/arm64/include/asm/mmu.h
@@ -67,6 +67,12 @@ 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;
 };
 
 DECLARE_PER_CPU_READ_MOSTLY(struct bp_hardening_data, bp_hardening_data);