[PATCH for-stable-4.14 34/48] KVM: arm64: Set SCTLR_EL2.DSSBS if SSBD is forcefully disabled and !vhe

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

From: Will Deacon <will.deacon@arm.com>

[ Upstream commit 7c36447ae5a090729e7b129f24705bb231a07e0b ]

When running without VHE, it is necessary to set SCTLR_EL2.DSSBS if SSBD
has been forcefully disabled on the kernel command-line.

Acked-by: Christoffer Dall <christoffer.dall@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 arch/arm64/include/asm/kvm_host.h | 11 +++++++++++
 arch/arm64/kvm/hyp/sysreg-sr.c    | 11 +++++++++++
 2 files changed, 22 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index b01ad3489bd8..f982c9d1d10b 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -356,6 +356,8 @@ struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);
 void __kvm_set_tpidr_el2(u64 tpidr_el2);
 DECLARE_PER_CPU(kvm_cpu_context_t, kvm_host_cpu_state);
 
+void __kvm_enable_ssbs(void);
+
 static inline void __cpu_init_hyp_mode(phys_addr_t pgd_ptr,
 				       unsigned long hyp_stack_ptr,
 				       unsigned long vector_ptr)
@@ -380,6 +382,15 @@ static inline void __cpu_init_hyp_mode(phys_addr_t pgd_ptr,
 		- (u64)kvm_ksym_ref(kvm_host_cpu_state);
 
 	kvm_call_hyp(__kvm_set_tpidr_el2, tpidr_el2);
+
+	/*
+	 * Disabling SSBD on a non-VHE system requires us to enable SSBS
+	 * at EL2.
+	 */
+	if (!has_vhe() && this_cpu_has_cap(ARM64_SSBS) &&
+	    arm64_get_ssbd_state() == ARM64_SSBD_FORCE_DISABLE) {
+		kvm_call_hyp(__kvm_enable_ssbs);
+	}
 }
 
 static inline void kvm_arch_hardware_unsetup(void) {}
diff --git a/arch/arm64/kvm/hyp/sysreg-sr.c b/arch/arm64/kvm/hyp/sysreg-sr.c
index e19d89cabf2a..3773311ffcd0 100644
--- a/arch/arm64/kvm/hyp/sysreg-sr.c
+++ b/arch/arm64/kvm/hyp/sysreg-sr.c
@@ -188,3 +188,14 @@ void __hyp_text __kvm_set_tpidr_el2(u64 tpidr_el2)
 {
 	asm("msr tpidr_el2, %0": : "r" (tpidr_el2));
 }
+
+void __hyp_text __kvm_enable_ssbs(void)
+{
+	u64 tmp;
+
+	asm volatile(
+	"mrs	%0, sctlr_el2\n"
+	"orr	%0, %0, %1\n"
+	"msr	sctlr_el2, %0"
+	: "=&r" (tmp) : "L" (SCTLR_ELx_DSSBS));
+}
-- 
2.20.1