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From: Mark Brown <broonie@kernel.org>
To: Marc Zyngier <maz@kernel.org>
Cc: Mark Brown <broonie@kernel.org>,
	kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: [PATCH v1 2/2] KVM: arm64: Add some more comments in kvm_hyp_handle_fpsimd()
Date: Mon, 24 Jan 2022 15:57:20 +0000	[thread overview]
Message-ID: <20220124155720.3943374-3-broonie@kernel.org> (raw)
In-Reply-To: <20220124155720.3943374-1-broonie@kernel.org>

The handling for FPSIMD/SVE traps is multi stage and involves some trap
manipulation which isn't quite so immediately obvious as might be desired
so add a few more comments.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
 arch/arm64/kvm/hyp/include/hyp/switch.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index 58e14f8ead23..1995808d8766 100644
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -173,6 +173,8 @@ static bool kvm_hyp_handle_fpsimd(struct kvm_vcpu *vcpu, u64 *exit_code)
 		return false;
 
 	/* Valid trap.  Switch the context: */
+
+	/* First disable enough traps to allow us to update the registers */
 	if (has_vhe()) {
 		reg = CPACR_EL1_FPEN;
 		if (sve_guest)
@@ -188,11 +190,13 @@ static bool kvm_hyp_handle_fpsimd(struct kvm_vcpu *vcpu, u64 *exit_code)
 	}
 	isb();
 
+	/* Write out the host state if it's in the registers */
 	if (vcpu->arch.flags & KVM_ARM64_FP_HOST) {
 		__fpsimd_save_state(vcpu->arch.host_fpsimd_state);
 		vcpu->arch.flags &= ~KVM_ARM64_FP_HOST;
 	}
 
+	/* Restore the guest state */
 	if (sve_guest)
 		__hyp_sve_restore_guest(vcpu);
 	else
-- 
2.30.2

_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

WARNING: multiple messages have this Message-ID (diff)
From: Mark Brown <broonie@kernel.org>
To: Marc Zyngier <maz@kernel.org>
Cc: James Morse <james.morse@arm.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, Mark Brown <broonie@kernel.org>
Subject: [PATCH v1 2/2] KVM: arm64: Add some more comments in kvm_hyp_handle_fpsimd()
Date: Mon, 24 Jan 2022 15:57:20 +0000	[thread overview]
Message-ID: <20220124155720.3943374-3-broonie@kernel.org> (raw)
In-Reply-To: <20220124155720.3943374-1-broonie@kernel.org>

The handling for FPSIMD/SVE traps is multi stage and involves some trap
manipulation which isn't quite so immediately obvious as might be desired
so add a few more comments.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
 arch/arm64/kvm/hyp/include/hyp/switch.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index 58e14f8ead23..1995808d8766 100644
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -173,6 +173,8 @@ static bool kvm_hyp_handle_fpsimd(struct kvm_vcpu *vcpu, u64 *exit_code)
 		return false;
 
 	/* Valid trap.  Switch the context: */
+
+	/* First disable enough traps to allow us to update the registers */
 	if (has_vhe()) {
 		reg = CPACR_EL1_FPEN;
 		if (sve_guest)
@@ -188,11 +190,13 @@ static bool kvm_hyp_handle_fpsimd(struct kvm_vcpu *vcpu, u64 *exit_code)
 	}
 	isb();
 
+	/* Write out the host state if it's in the registers */
 	if (vcpu->arch.flags & KVM_ARM64_FP_HOST) {
 		__fpsimd_save_state(vcpu->arch.host_fpsimd_state);
 		vcpu->arch.flags &= ~KVM_ARM64_FP_HOST;
 	}
 
+	/* Restore the guest state */
 	if (sve_guest)
 		__hyp_sve_restore_guest(vcpu);
 	else
-- 
2.30.2


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  parent reply	other threads:[~2022-01-24 15:58 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-24 15:57 [PATCH v1 0/2] KVM: arm64: Additional documentation of the FP code Mark Brown
2022-01-24 15:57 ` Mark Brown
2022-01-24 15:57 ` [PATCH v1 1/2] KVM: arm64: Add comments for context flush and sync callbacks Mark Brown
2022-01-24 15:57   ` Mark Brown
2022-01-24 15:57 ` Mark Brown [this message]
2022-01-24 15:57   ` [PATCH v1 2/2] KVM: arm64: Add some more comments in kvm_hyp_handle_fpsimd() Mark Brown
2022-02-08 17:37 ` [PATCH v1 0/2] KVM: arm64: Additional documentation of the FP code Marc Zyngier
2022-02-08 17:37   ` Marc Zyngier

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