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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 2/4] KVM: arm64: Predicate FPSIMD vcpu flags on feature support
Date: Mon, 13 Jul 2020 22:05:03 +0100
Message-ID: <20200713210505.2959828-3-ascull@google.com> (raw)
In-Reply-To: <20200713210505.2959828-1-ascull@google.com>

If the system doesn't support FPSIMD features then the flags must never
be set. These are the same feature checks performed by hyp when handling
an FPSIMD trap.

Signed-off-by: Andrew Scull <ascull@google.com>
---
 arch/arm64/kvm/fpsimd.c | 24 +++++++++++++++++++-----
 1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c
index 3e081d556e81..c6b3197f6754 100644
--- a/arch/arm64/kvm/fpsimd.c
+++ b/arch/arm64/kvm/fpsimd.c
@@ -52,7 +52,7 @@ int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu)
  * Prepare vcpu for saving the host's FPSIMD state and loading the guest's.
  * The actual loading is done by the FPSIMD access trap taken to hyp.
  *
- * Here, we just set the correct metadata to indicate that the FPSIMD
+ * Here, we just set the correct metadata to indicate whether 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.
@@ -63,15 +63,29 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
 	BUG_ON(!current->mm);
 
 	vcpu->arch.flags &= ~(KVM_ARM64_FP_ENABLED |
+			      KVM_ARM64_FP_HOST |
 			      KVM_ARM64_HOST_SVE_IN_USE |
 			      KVM_ARM64_HOST_SVE_ENABLED);
+
+	if (!system_supports_fpsimd())
+		return;
+
+	/*
+	 * Having just come from the user task, if any FP state is loaded it
+	 * will be that of the task. Make a note of this but, just before
+	 * entering the vcpu, it will be double checked that the loaded FP
+	 * state isn't transient because things could change between now and
+	 * then.
+	 */
 	vcpu->arch.flags |= KVM_ARM64_FP_HOST;
 
-	if (test_thread_flag(TIF_SVE))
-		vcpu->arch.flags |= KVM_ARM64_HOST_SVE_IN_USE;
+	if (system_supports_sve()) {
+		if (test_thread_flag(TIF_SVE))
+			vcpu->arch.flags |= KVM_ARM64_HOST_SVE_IN_USE;
 
-	if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN)
-		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;
+	}
 }
 
 /*
-- 
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 ` Andrew Scull [this message]
2020-07-22 16:23   ` [PATCH v2 2/4] KVM: arm64: Predicate FPSIMD vcpu flags on feature support Dave Martin
2020-07-13 21:05 ` [PATCH v2 3/4] KVM: arm64: Leave vcpu FPSIMD synchronization in host Andrew Scull
2020-07-22 16:24   ` 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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