Commit 5bdf3437 authored Nov 16, 2021 by James Morse

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



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>

parent 1b33d486

arch/arm64/include/asm/kvm_host.h

+5 −0

Original line number	Diff line number	Diff line
		@@ -714,6 +714,11 @@ static inline void kvm_init_host_cpu_context(struct kvm_cpu_context *cpu_ctxt)
		ctxt_sys_reg(cpu_ctxt, MPIDR_EL1) = read_cpuid_mpidr();
		}

		static inline bool kvm_system_needs_idmapped_vectors(void)
		{
		return cpus_have_const_cap(ARM64_SPECTRE_V3A);
		}

		void kvm_arm_vcpu_ptrauth_trap(struct kvm_vcpu *vcpu);

		static inline void kvm_arch_hardware_unsetup(void) {}

arch/arm64/kvm/arm.c

+1 −4

Original line number	Diff line number	Diff line
		@@ -1491,10 +1491,7 @@ static int kvm_init_vector_slots(void)
		base = kern_hyp_va(kvm_ksym_ref(__bp_harden_hyp_vecs));
		kvm_init_vector_slot(base, HYP_VECTOR_SPECTRE_DIRECT);

		if (!cpus_have_const_cap(ARM64_SPECTRE_V3A))
		return 0;

		if (!has_vhe()) {
		if (kvm_system_needs_idmapped_vectors() && !has_vhe()) {
		err = create_hyp_exec_mappings(__pa_symbol(__bp_harden_hyp_vecs),
		__BP_HARDEN_HYP_VECS_SZ, &base);
		if (err)

arch/arm64/kvm/hyp/nvhe/mm.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -148,8 +148,10 @@ int hyp_map_vectors(void)
		phys_addr_t phys;
		void *bp_base;

		if (!cpus_have_const_cap(ARM64_SPECTRE_V3A))
		if (!kvm_system_needs_idmapped_vectors()) {
		__hyp_bp_vect_base = __bp_harden_hyp_vecs;
		return 0;
		}

		phys = __hyp_pa(__bp_harden_hyp_vecs);
		bp_base = (void *)__pkvm_create_private_mapping(phys,