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Subject[PATCH 4.19 090/114] KVM: arm64: Set SCTLR_EL2.DSSBS if SSBD is forcefully disabled and !vhe
Date
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/arm64/include/asm/kvm_host.h | 11 +++++++++++
arch/arm64/kvm/hyp/sysreg-sr.c | 11 +++++++++++
2 files changed, 22 insertions(+)

--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -398,6 +398,8 @@ struct kvm_vcpu *kvm_mpidr_to_vcpu(struc

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)
@@ -418,6 +420,15 @@ static inline void __cpu_init_hyp_mode(p
*/
BUG_ON(!static_branch_likely(&arm64_const_caps_ready));
__kvm_call_hyp((void *)pgd_ptr, hyp_stack_ptr, vector_ptr, 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 bool kvm_arch_check_sve_has_vhe(void)
--- a/arch/arm64/kvm/hyp/sysreg-sr.c
+++ b/arch/arm64/kvm/hyp/sysreg-sr.c
@@ -293,3 +293,14 @@ void kvm_vcpu_put_sysregs(struct kvm_vcp

vcpu->arch.sysregs_loaded_on_cpu = false;
}
+
+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));
+}

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