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From: Andrew Scull <ascull@google.com>
To: kvmarm@lists.cs.columbia.edu
Cc: maz@kernel.org, kernel-team@android.com, dave.martin@arm.com
Subject: [PATCH v2 3/4] KVM: arm64: Leave vcpu FPSIMD synchronization in host
Date: Mon, 13 Jul 2020 22:05:04 +0100
Message-ID: <20200713210505.2959828-4-ascull@google.com> (raw)
In-Reply-To: <20200713210505.2959828-1-ascull@google.com>

The task state can be checked by the host and the vcpu flags updated
before calling into hyp. Hyp simply acts on the state provided to it by
the host and updates it when switching to the vcpu state.

Signed-off-by: Andrew Scull <ascull@google.com>
---
 arch/arm64/include/asm/kvm_host.h       |  3 ++-
 arch/arm64/kvm/arm.c                    |  4 +++-
 arch/arm64/kvm/fpsimd.c                 | 19 ++++++++++++++++++-
 arch/arm64/kvm/hyp/include/hyp/switch.h | 19 -------------------
 arch/arm64/kvm/hyp/nvhe/switch.c        |  3 +--
 arch/arm64/kvm/hyp/vhe/switch.c         |  3 +--
 6 files changed, 25 insertions(+), 26 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index b06f24b5f443..1a062d44b395 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -616,7 +616,8 @@ int kvm_arm_vcpu_arch_has_attr(struct kvm_vcpu *vcpu,
 /* Guest/host FPSIMD coordination helpers */
 int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu);
 void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu);
-void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu);
+void kvm_arch_vcpu_sync_fp_before_run(struct kvm_vcpu *vcpu);
+void kvm_arch_vcpu_sync_fp_after_run(struct kvm_vcpu *vcpu);
 void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu);
 
 static inline bool kvm_pmu_counter_deferred(struct perf_event_attr *attr)
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 98f05bdac3c1..c91b0a66bf20 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -682,6 +682,8 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
 
 		local_irq_disable();
 
+		kvm_arch_vcpu_sync_fp_before_run(vcpu);
+
 		kvm_vgic_flush_hwstate(vcpu);
 
 		/*
@@ -769,7 +771,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
 		if (static_branch_unlikely(&userspace_irqchip_in_use))
 			kvm_timer_sync_user(vcpu);
 
-		kvm_arch_vcpu_ctxsync_fp(vcpu);
+		kvm_arch_vcpu_sync_fp_after_run(vcpu);
 
 		/*
 		 * We may have taken a host interrupt in HYP mode (ie
diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c
index c6b3197f6754..2779cc11f3dd 100644
--- a/arch/arm64/kvm/fpsimd.c
+++ b/arch/arm64/kvm/fpsimd.c
@@ -88,13 +88,30 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
 	}
 }
 
+void kvm_arch_vcpu_sync_fp_before_run(struct kvm_vcpu *vcpu)
+{
+	WARN_ON_ONCE(!irqs_disabled());
+
+	if (!system_supports_fpsimd())
+		return;
+
+	/*
+	 * If the CPU's FP state is transient, there is no need to save the
+	 * current state. Without further information, it must also be assumed
+	 * that the vcpu's state is not loaded.
+	 */
+	if (test_thread_flag(TIF_FOREIGN_FPSTATE))
+		vcpu->arch.flags &= ~(KVM_ARM64_FP_ENABLED |
+				      KVM_ARM64_FP_HOST);
+}
+
 /*
  * 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)
+void kvm_arch_vcpu_sync_fp_after_run(struct kvm_vcpu *vcpu)
 {
 	WARN_ON_ONCE(!irqs_disabled());
 
diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index 0511af14dc81..65cde758abad 100644
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -25,28 +25,9 @@
 #include <asm/fpsimd.h>
 #include <asm/debug-monitors.h>
 #include <asm/processor.h>
-#include <asm/thread_info.h>
 
 extern const char __hyp_panic_string[];
 
-/* Check whether the FP regs were dirtied while in the host-side run loop: */
-static inline bool update_fp_enabled(struct kvm_vcpu *vcpu)
-{
-	/*
-	 * When the system doesn't support FP/SIMD, we cannot rely on
-	 * the _TIF_FOREIGN_FPSTATE flag. However, we always inject an
-	 * abort on the very first access to FP and thus we should never
-	 * see KVM_ARM64_FP_ENABLED. For added safety, make sure we always
-	 * trap the accesses.
-	 */
-	if (!system_supports_fpsimd() ||
-	    vcpu->arch.host_thread_info->flags & _TIF_FOREIGN_FPSTATE)
-		vcpu->arch.flags &= ~(KVM_ARM64_FP_ENABLED |
-				      KVM_ARM64_FP_HOST);
-
-	return !!(vcpu->arch.flags & KVM_ARM64_FP_ENABLED);
-}
-
 /* Save the 32-bit only FPSIMD system register state */
 static inline void __fpsimd_save_fpexc32(struct kvm_vcpu *vcpu)
 {
diff --git a/arch/arm64/kvm/hyp/nvhe/switch.c b/arch/arm64/kvm/hyp/nvhe/switch.c
index 341be2f2f312..3b7306003917 100644
--- a/arch/arm64/kvm/hyp/nvhe/switch.c
+++ b/arch/arm64/kvm/hyp/nvhe/switch.c
@@ -25,7 +25,6 @@
 #include <asm/fpsimd.h>
 #include <asm/debug-monitors.h>
 #include <asm/processor.h>
-#include <asm/thread_info.h>
 
 static void __activate_traps(struct kvm_vcpu *vcpu)
 {
@@ -36,7 +35,7 @@ static void __activate_traps(struct kvm_vcpu *vcpu)
 
 	val = CPTR_EL2_DEFAULT;
 	val |= CPTR_EL2_TTA | CPTR_EL2_TZ | CPTR_EL2_TAM;
-	if (!update_fp_enabled(vcpu)) {
+	if (!(vcpu->arch.flags & KVM_ARM64_FP_ENABLED)) {
 		val |= CPTR_EL2_TFP;
 		__activate_traps_fpsimd32(vcpu);
 	}
diff --git a/arch/arm64/kvm/hyp/vhe/switch.c b/arch/arm64/kvm/hyp/vhe/switch.c
index c52d714e0d75..0c08c9123ce5 100644
--- a/arch/arm64/kvm/hyp/vhe/switch.c
+++ b/arch/arm64/kvm/hyp/vhe/switch.c
@@ -24,7 +24,6 @@
 #include <asm/fpsimd.h>
 #include <asm/debug-monitors.h>
 #include <asm/processor.h>
-#include <asm/thread_info.h>
 
 const char __hyp_panic_string[] = "HYP panic:\nPS:%08llx PC:%016llx ESR:%08llx\nFAR:%016llx HPFAR:%016llx PAR:%016llx\nVCPU:%p\n";
 
@@ -49,7 +48,7 @@ static void __activate_traps(struct kvm_vcpu *vcpu)
 
 	val |= CPTR_EL2_TAM;
 
-	if (update_fp_enabled(vcpu)) {
+	if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) {
 		if (vcpu_has_sve(vcpu))
 			val |= CPACR_EL1_ZEN;
 	} else {
-- 
2.27.0.383.g050319c2ae-goog

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  parent reply index

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-13 21:05 [PATCH v2 0/4] Manage vcpu flags from the host Andrew Scull
2020-07-13 21:05 ` [PATCH v2 1/4] KVM: arm64: Leave KVM_ARM64_DEBUG_DIRTY updates to " Andrew Scull
2020-07-22 16:24   ` Dave Martin
2020-07-13 21:05 ` [PATCH v2 2/4] KVM: arm64: Predicate FPSIMD vcpu flags on feature support Andrew Scull
2020-07-22 16:23   ` Dave Martin
2020-07-13 21:05 ` Andrew Scull [this message]
2020-07-22 16:24   ` [PATCH v2 3/4] KVM: arm64: Leave vcpu FPSIMD synchronization in host Dave Martin
2020-07-13 21:05 ` [PATCH v2 4/4] KVM: arm64: Stop mapping host task thread flags to hyp Andrew Scull
2020-07-22 16:24   ` Dave Martin
2020-07-22 16:24 ` [PATCH v2 0/4] Manage vcpu flags from the host Dave Martin
2020-07-22 16:36   ` Marc Zyngier
2020-07-22 16:40     ` Dave Martin

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