1 files changed, 71 insertions, 60 deletions

diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c
index 525010504f9d..7f6e43d25691 100644
--- a/arch/arm64/kvm/fpsimd.c
+++ b/arch/arm64/kvm/fpsimd.c
@@ -7,11 +7,10 @@
  */
 #include <linux/irqflags.h>
 #include <linux/sched.h>
-#include <linux/thread_info.h>
 #include <linux/kvm_host.h>
 #include <asm/fpsimd.h>
 #include <asm/kvm_asm.h>
-#include <asm/kvm_host.h>
+#include <asm/kvm_hyp.h>
 #include <asm/kvm_mmu.h>
 #include <asm/sysreg.h>
 
@@ -26,27 +25,19 @@
  */
 int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu)
 {
+	struct user_fpsimd_state *fpsimd = &current->thread.uw.fpsimd_state;
 	int ret;
 
-	struct thread_info *ti = &current->thread_info;
-	struct user_fpsimd_state *fpsimd = &current->thread.uw.fpsimd_state;
+	/* pKVM has its own tracking of the host fpsimd state. */
+	if (is_protected_kvm_enabled())
+		return 0;
 
-	/*
-	 * Make sure the host task thread flags and fpsimd state are
-	 * visible to hyp:
-	 */
-	ret = create_hyp_mappings(ti, ti + 1, PAGE_HYP);
+	/* Make sure the host task fpsimd state is visible to hyp: */
+	ret = kvm_share_hyp(fpsimd, fpsimd + 1);
 	if (ret)
-		goto error;
+		return ret;
 
-	ret = create_hyp_mappings(fpsimd, fpsimd + 1, PAGE_HYP);
-	if (ret)
-		goto error;
-
-	vcpu->arch.host_thread_info = kern_hyp_va(ti);
-	vcpu->arch.host_fpsimd_state = kern_hyp_va(fpsimd);
-error:
-	return ret;
+	return 0;
 }
 
 /*
@@ -55,43 +46,75 @@ error:
  *
  * Here, we just set the correct metadata to indicate that the FPSIMD
  * state in the cpu regs (if any) belongs to current on the host.
- *
- * TIF_SVE is backed up here, since it may get clobbered with guest state.
- * This flag is restored by kvm_arch_vcpu_put_fp(vcpu).
  */
 void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
 {
 	BUG_ON(!current->mm);
 
-	vcpu->arch.flags &= ~(KVM_ARM64_FP_ENABLED |
-			      KVM_ARM64_HOST_SVE_IN_USE |
-			      KVM_ARM64_HOST_SVE_ENABLED);
-	vcpu->arch.flags |= KVM_ARM64_FP_HOST;
+	if (!system_supports_fpsimd())
+		return;
 
-	if (test_thread_flag(TIF_SVE))
-		vcpu->arch.flags |= KVM_ARM64_HOST_SVE_IN_USE;
+	/*
+	 * 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}.
+	 */
+	fpsimd_save_and_flush_cpu_state();
+	*host_data_ptr(fp_owner) = FP_STATE_FREE;
 
-	if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN)
-		vcpu->arch.flags |= KVM_ARM64_HOST_SVE_ENABLED;
+	WARN_ON_ONCE(system_supports_sme() && read_sysreg_s(SYS_SVCR));
 }
 
 /*
- * If the guest FPSIMD state was loaded, update the host's context
- * tracking data mark the CPU FPSIMD regs as dirty and belonging to vcpu
- * so that they will be written back if the kernel clobbers them due to
- * kernel-mode NEON before re-entry into the guest.
+ * 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))
+		*host_data_ptr(fp_owner) = FP_STATE_FREE;
+}
+
+/*
+ * Called just after exiting the guest. If the guest FPSIMD state
+ * was loaded, update the host's context tracking data mark the CPU
+ * FPSIMD regs as dirty and belonging to vcpu so that they will be
+ * written back if the kernel clobbers them due to kernel-mode NEON
+ * before re-entry into the guest.
  */
 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) {
-		fpsimd_bind_state_to_cpu(&vcpu->arch.ctxt.gp_regs.fp_regs,
-					 vcpu->arch.sve_state,
-					 vcpu->arch.sve_max_vl);
+	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.
+		 */
+		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 = &__vcpu_sys_reg(vcpu, SVCR);
+		fp_state.fpmr = &__vcpu_sys_reg(vcpu, 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));
 	}
 }
 
@@ -104,34 +127,22 @@ void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu)
 void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
 {
 	unsigned long flags;
-	bool host_has_sve = system_supports_sve();
-	bool guest_has_sve = vcpu_has_sve(vcpu);
 
 	local_irq_save(flags);
 
-	if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) {
-		u64 *guest_zcr = &vcpu->arch.ctxt.sys_regs[ZCR_EL1];
-
-		fpsimd_save_and_flush_cpu_state();
-
-		if (guest_has_sve)
-			*guest_zcr = read_sysreg_s(SYS_ZCR_EL12);
-	} else if (host_has_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,
-			   vcpu->arch.flags & KVM_ARM64_HOST_SVE_IN_USE);
-
 	local_irq_restore(flags);
 }