[PATCH 3/7] KVM: arm64: Add save/restore support for FPMR

[Marc Zyngier]

Just like the rest of the FP/SIMD state, FPMR needs to be context
switched.

The only interesting thing here is that we need to treat the pKVM
part a bit differently, as the host FP state is never written back
to the vcpu thread, but instead stored locally and eagerly restored.

Signed-off-by: Marc Zyngier <maz at kernel.org>
---
 arch/arm64/include/asm/kvm_host.h  | 10 ++++++++++
 arch/arm64/kvm/fpsimd.c            |  1 +
 arch/arm64/kvm/hyp/nvhe/hyp-main.c |  4 ++++
 arch/arm64/kvm/hyp/nvhe/switch.c   | 10 ++++++++++
 arch/arm64/kvm/hyp/vhe/switch.c    |  4 ++++
 5 files changed, 29 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index a14c18e8b173a..764d23082eb91 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -599,6 +599,16 @@ struct kvm_host_data {
 		struct cpu_sve_state *sve_state;
 	};
 
+	union {
+		/* HYP VA pointer to the host storage for FPMR */
+		u64	*fpmr_ptr;
+		/*
+		 * Used by pKVM only, as it needs to provide storage
+		 * for the host
+		 */
+		u64	fpmr;
+	};
+
 	/* Ownership of the FP regs */
 	enum {
 		FP_STATE_FREE,
diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c
index 4cb8ad5d69a80..ea5484ce1f3ba 100644
--- a/arch/arm64/kvm/fpsimd.c
+++ b/arch/arm64/kvm/fpsimd.c
@@ -63,6 +63,7 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
 	 */
 	*host_data_ptr(fp_owner) = FP_STATE_HOST_OWNED;
 	*host_data_ptr(fpsimd_state) = kern_hyp_va(&current->thread.uw.fpsimd_state);
+	*host_data_ptr(fpmr_ptr) = kern_hyp_va(&current->thread.uw.fpmr);
 
 	vcpu_clear_flag(vcpu, HOST_SVE_ENABLED);
 	if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN)
diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
index f43d845f3c4ec..6b14a2c13e287 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
@@ -78,6 +78,10 @@ static void fpsimd_sve_sync(struct kvm_vcpu *vcpu)
 	else
 		__fpsimd_restore_state(*host_data_ptr(fpsimd_state));
 
+	if (system_supports_fpmr() &&
+	    kvm_has_feat(kern_hyp_va(vcpu->kvm), ID_AA64PFR2_EL1, FPMR, IMP))
+		write_sysreg_s(*host_data_ptr(fpmr), SYS_FPMR);
+
 	*host_data_ptr(fp_owner) = FP_STATE_HOST_OWNED;
 }
 
diff --git a/arch/arm64/kvm/hyp/nvhe/switch.c b/arch/arm64/kvm/hyp/nvhe/switch.c
index 6af179c6356d6..47d24ecd68fec 100644
--- a/arch/arm64/kvm/hyp/nvhe/switch.c
+++ b/arch/arm64/kvm/hyp/nvhe/switch.c
@@ -198,6 +198,16 @@ static void kvm_hyp_save_fpsimd_host(struct kvm_vcpu *vcpu)
 	} else {
 		__fpsimd_save_state(*host_data_ptr(fpsimd_state));
 	}
+
+	if (system_supports_fpmr() &&
+	    kvm_has_feat(kern_hyp_va(vcpu->kvm), ID_AA64PFR2_EL1, FPMR, IMP)) {
+		u64 fpmr = read_sysreg_s(SYS_FPMR);
+
+		if (unlikely(is_protected_kvm_enabled()))
+			*host_data_ptr(fpmr) = fpmr;
+		else
+			**host_data_ptr(fpmr_ptr) = fpmr;
+	}
 }
 
 static const exit_handler_fn hyp_exit_handlers[] = {
diff --git a/arch/arm64/kvm/hyp/vhe/switch.c b/arch/arm64/kvm/hyp/vhe/switch.c
index 77010b76c150f..a307c1d5ac874 100644
--- a/arch/arm64/kvm/hyp/vhe/switch.c
+++ b/arch/arm64/kvm/hyp/vhe/switch.c
@@ -312,6 +312,10 @@ static bool kvm_hyp_handle_eret(struct kvm_vcpu *vcpu, u64 *exit_code)
 static void kvm_hyp_save_fpsimd_host(struct kvm_vcpu *vcpu)
 {
 	__fpsimd_save_state(*host_data_ptr(fpsimd_state));
+
+	if (system_supports_fpmr() &&
+	    kvm_has_feat(vcpu->kvm, ID_AA64PFR2_EL1, FPMR, IMP))
+		**host_data_ptr(fpmr_ptr) = read_sysreg_s(SYS_FPMR);
 }
 
 static bool kvm_hyp_handle_tlbi_el2(struct kvm_vcpu *vcpu, u64 *exit_code)
-- 
2.39.2