[PATCH 08/10] KVM: arm64: Add a nVHE-specific SVE VQ reset hypercall

[Marc Zyngier <maz@kernel.org>]

ZCR_EL2 controls the upper bound for ZCR_EL1, and is set to
a potentially lower limit when the guest uses SVE.

In order to restore the SVE state on the EL1 host, we must first
reset ZCR_EL2 to its original value.

Provide a hypervall that perform this reset.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/include/asm/kvm_asm.h   | 1 +
 arch/arm64/include/asm/kvm_host.h  | 4 +++-
 arch/arm64/kvm/hyp/nvhe/hyp-main.c | 8 ++++++++
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
index 22d933e9b59e..7ae947934ec9 100644
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -57,6 +57,7 @@
 #define __KVM_HOST_SMCCC_FUNC___kvm_get_mdcr_el2		12
 #define __KVM_HOST_SMCCC_FUNC___vgic_v3_save_aprs		13
 #define __KVM_HOST_SMCCC_FUNC___vgic_v3_restore_aprs		14
+#define __KVM_HOST_SMCCC_FUNC___kvm_reset_sve_vq		15
 
 #ifndef __ASSEMBLY__
 
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index c4afe3d3397f..9108ccc80653 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -593,7 +593,9 @@ int kvm_test_age_hva(struct kvm *kvm, unsigned long hva);
 void kvm_arm_halt_guest(struct kvm *kvm);
 void kvm_arm_resume_guest(struct kvm *kvm);
 
-#define kvm_call_hyp_nvhe(f, ...)						\
+static inline void __kvm_reset_sve_vq(void) {}
+
+#define kvm_call_hyp_nvhe(f, ...)					\
 	({								\
 		struct arm_smccc_res res;				\
 									\
diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
index f012f8665ecc..9fdd8d6e3554 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
@@ -106,6 +106,13 @@ static void handle___vgic_v3_restore_aprs(struct kvm_cpu_context *host_ctxt)
 	__vgic_v3_restore_aprs(kern_hyp_va(cpu_if));
 }
 
+static void handle___kvm_reset_sve_vq(struct kvm_cpu_context *host_ctxt)
+{
+	if (system_supports_sve() &&
+	    read_sysreg_s(SYS_ZCR_EL2) != ZCR_ELx_LEN_MASK)
+		write_sysreg_s(ZCR_ELx_LEN_MASK, SYS_ZCR_EL2);
+}
+
 typedef void (*hcall_t)(struct kvm_cpu_context *);
 
 #define HANDLE_FUNC(x)	[__KVM_HOST_SMCCC_FUNC_##x] = (hcall_t)handle_##x
@@ -125,6 +132,7 @@ static const hcall_t host_hcall[] = {
 	HANDLE_FUNC(__kvm_get_mdcr_el2),
 	HANDLE_FUNC(__vgic_v3_save_aprs),
 	HANDLE_FUNC(__vgic_v3_restore_aprs),
+	HANDLE_FUNC(__kvm_reset_sve_vq),
 };
 
 static void handle_host_hcall(struct kvm_cpu_context *host_ctxt)
-- 
2.29.2