1 files changed, 49 insertions, 105 deletions

diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c
index 6012b08ecb14..8f6c8f57c6b9 100644
--- a/arch/arm64/kvm/fpsimd.c
+++ b/arch/arm64/kvm/fpsimd.c
@@ -14,19 +14,6 @@
 #include <asm/kvm_mmu.h>
 #include <asm/sysreg.h>
 
-void kvm_vcpu_unshare_task_fp(struct kvm_vcpu *vcpu)
-{
-	struct task_struct *p = vcpu->arch.parent_task;
-	struct user_fpsimd_state *fpsimd;
-
-	if (!is_protected_kvm_enabled() || !p)
-		return;
-
-	fpsimd = &p->thread.uw.fpsimd_state;
-	kvm_unshare_hyp(fpsimd, fpsimd + 1);
-	put_task_struct(p);
-}
-
 /*
  * Called on entry to KVM_RUN unless this vcpu previously ran at least
  * once and the most recent prior KVM_RUN for this vcpu was called from
@@ -38,30 +25,18 @@ void kvm_vcpu_unshare_task_fp(struct kvm_vcpu *vcpu)
  */
 int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu)
 {
-	int ret;
-
 	struct user_fpsimd_state *fpsimd = &current->thread.uw.fpsimd_state;
+	int ret;
 
-	kvm_vcpu_unshare_task_fp(vcpu);
+	/* pKVM has its own tracking of the host fpsimd state. */
+	if (is_protected_kvm_enabled())
+		return 0;
 
 	/* Make sure the host task fpsimd state is visible to hyp: */
 	ret = kvm_share_hyp(fpsimd, fpsimd + 1);
 	if (ret)
 		return ret;
 
-	vcpu->arch.host_fpsimd_state = kern_hyp_va(fpsimd);
-
-	/*
-	 * We need to keep current's task_struct pinned until its data has been
-	 * unshared with the hypervisor to make sure it is not re-used by the
-	 * kernel and donated to someone else while already shared -- see
-	 * kvm_vcpu_unshare_task_fp() for the matching put_task_struct().
-	 */
-	if (is_protected_kvm_enabled()) {
-		get_task_struct(current);
-		vcpu->arch.parent_task = current;
-	}
-
 	return 0;
 }
 
@@ -75,48 +50,35 @@ int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu)
 void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
 {
 	BUG_ON(!current->mm);
-	BUG_ON(test_thread_flag(TIF_SVE));
 
-	vcpu->arch.flags &= ~KVM_ARM64_FP_ENABLED;
-	vcpu->arch.flags |= KVM_ARM64_FP_HOST;
-
-	vcpu->arch.flags &= ~KVM_ARM64_HOST_SVE_ENABLED;
-	if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN)
-		vcpu->arch.flags |= KVM_ARM64_HOST_SVE_ENABLED;
+	if (!system_supports_fpsimd())
+		return;
 
 	/*
-	 * We don't currently support SME guests but if we leave
-	 * things in streaming mode then when the guest starts running
-	 * FPSIMD or SVE code it may generate SME traps so as a
-	 * special case if we are in streaming mode we force the host
-	 * state to be saved now and exit streaming mode so that we
-	 * don't have to handle any SME traps for valid guest
-	 * operations. Do this for ZA as well for now for simplicity.
+	 * Ensure that any host FPSIMD/SVE/SME state is saved and unbound such
+	 * that the host kernel is responsible for restoring this state upon
+	 * return to userspace, and the hyp code doesn't need to save anything.
+	 *
+	 * When the host may use SME, fpsimd_save_and_flush_cpu_state() ensures
+	 * that PSTATE.{SM,ZA} == {0,0}.
 	 */
-	if (system_supports_sme()) {
-		vcpu->arch.flags &= ~KVM_ARM64_HOST_SME_ENABLED;
-		if (read_sysreg(cpacr_el1) & CPACR_EL1_SMEN_EL0EN)
-			vcpu->arch.flags |= KVM_ARM64_HOST_SME_ENABLED;
-
-		if (read_sysreg_s(SYS_SVCR) &
-		    (SVCR_SM_MASK | SVCR_ZA_MASK)) {
-			vcpu->arch.flags &= ~KVM_ARM64_FP_HOST;
-			fpsimd_save_and_flush_cpu_state();
-		}
-	}
+	fpsimd_save_and_flush_cpu_state();
+	*host_data_ptr(fp_owner) = FP_STATE_FREE;
+
+	WARN_ON_ONCE(system_supports_sme() && read_sysreg_s(SYS_SVCR));
 }
 
 /*
- * Called just before entering the guest once we are no longer
- * preemptable. Syncs the host's TIF_FOREIGN_FPSTATE with the KVM
- * mirror of the flag used by the hypervisor.
+ * Called just before entering the guest once we are no longer preemptible
+ * and interrupts are disabled. If we have managed to run anything using
+ * FP while we were preemptible (such as off the back of an interrupt),
+ * then neither the host nor the guest own the FP hardware (and it was the
+ * responsibility of the code that used FP to save the existing state).
  */
 void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu)
 {
 	if (test_thread_flag(TIF_FOREIGN_FPSTATE))
-		vcpu->arch.flags |= KVM_ARM64_FP_FOREIGN_FPSTATE;
-	else
-		vcpu->arch.flags &= ~KVM_ARM64_FP_FOREIGN_FPSTATE;
+		*host_data_ptr(fp_owner) = FP_STATE_FREE;
 }
 
 /*
@@ -128,20 +90,31 @@ void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu)
  */
 void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu)
 {
+	struct cpu_fp_state fp_state;
+
 	WARN_ON_ONCE(!irqs_disabled());
 
-	if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) {
+	if (guest_owns_fp_regs()) {
 		/*
 		 * Currently we do not support SME guests so SVCR is
 		 * always 0 and we just need a variable to point to.
 		 */
-		fpsimd_bind_state_to_cpu(&vcpu->arch.ctxt.fp_regs,
-					 vcpu->arch.sve_state,
-					 vcpu->arch.sve_max_vl,
-					 NULL, 0, &vcpu->arch.svcr);
+		fp_state.st = &vcpu->arch.ctxt.fp_regs;
+		fp_state.sve_state = vcpu->arch.sve_state;
+		fp_state.sve_vl = vcpu->arch.sve_max_vl;
+		fp_state.sme_state = NULL;
+		fp_state.svcr = __ctxt_sys_reg(&vcpu->arch.ctxt, SVCR);
+		fp_state.fpmr = __ctxt_sys_reg(&vcpu->arch.ctxt, FPMR);
+		fp_state.fp_type = &vcpu->arch.fp_type;
+
+		if (vcpu_has_sve(vcpu))
+			fp_state.to_save = FP_STATE_SVE;
+		else
+			fp_state.to_save = FP_STATE_FPSIMD;
+
+		fpsimd_bind_state_to_cpu(&fp_state);
 
 		clear_thread_flag(TIF_FOREIGN_FPSTATE);
-		update_thread_flag(TIF_SVE, vcpu_has_sve(vcpu));
 	}
 }
 
@@ -157,48 +130,19 @@ void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
 
 	local_irq_save(flags);
 
-	/*
-	 * If we have VHE then the Hyp code will reset CPACR_EL1 to
-	 * CPACR_EL1_DEFAULT and we need to reenable SME.
-	 */
-	if (has_vhe() && system_supports_sme()) {
-		/* Also restore EL0 state seen on entry */
-		if (vcpu->arch.flags & KVM_ARM64_HOST_SME_ENABLED)
-			sysreg_clear_set(CPACR_EL1, 0,
-					 CPACR_EL1_SMEN_EL0EN |
-					 CPACR_EL1_SMEN_EL1EN);
-		else
-			sysreg_clear_set(CPACR_EL1,
-					 CPACR_EL1_SMEN_EL0EN,
-					 CPACR_EL1_SMEN_EL1EN);
-	}
-
-	if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) {
-		if (vcpu_has_sve(vcpu)) {
-			__vcpu_sys_reg(vcpu, ZCR_EL1) = read_sysreg_el1(SYS_ZCR);
-
-			/* Restore the VL that was saved when bound to the CPU */
-			if (!has_vhe())
-				sve_cond_update_zcr_vq(vcpu_sve_max_vq(vcpu) - 1,
-						       SYS_ZCR_EL1);
-		}
-
-		fpsimd_save_and_flush_cpu_state();
-	} else if (has_vhe() && system_supports_sve()) {
+	if (guest_owns_fp_regs()) {
 		/*
-		 * The FPSIMD/SVE state in the CPU has not been touched, and we
-		 * have SVE (and VHE): CPACR_EL1 (alias CPTR_EL2) has been
-		 * reset to CPACR_EL1_DEFAULT by the Hyp code, disabling SVE
-		 * for EL0.  To avoid spurious traps, restore the trap state
-		 * seen by kvm_arch_vcpu_load_fp():
+		 * Flush (save and invalidate) the fpsimd/sve state so that if
+		 * the host tries to use fpsimd/sve, it's not using stale data
+		 * from the guest.
+		 *
+		 * Flushing the state sets the TIF_FOREIGN_FPSTATE bit for the
+		 * context unconditionally, in both nVHE and VHE. This allows
+		 * the kernel to restore the fpsimd/sve state, including ZCR_EL1
+		 * when needed.
 		 */
-		if (vcpu->arch.flags & KVM_ARM64_HOST_SVE_ENABLED)
-			sysreg_clear_set(CPACR_EL1, 0, CPACR_EL1_ZEN_EL0EN);
-		else
-			sysreg_clear_set(CPACR_EL1, CPACR_EL1_ZEN_EL0EN, 0);
+		fpsimd_save_and_flush_cpu_state();
 	}
 
-	update_thread_flag(TIF_SVE, 0);
-
 	local_irq_restore(flags);
 }