[PATCH v3 26/27] KVM: arm64: Move HCRX_EL2 switch to load/put on VHE systems

From: Marc Zyngier <maz@kernel.org>
To: kvmarm@lists.linux.dev, kvm@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	Eric Auger <eric.auger@redhat.com>,
	Mark Brown <broonie@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Will Deacon <will@kernel.org>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	Andre Przywara <andre.przywara@arm.com>,
	Chase Conklin <chase.conklin@arm.com>,
	Ganapatrao Kulkarni <gankulkarni@os.amperecomputing.com>,
	Darren Hart <darren@os.amperecomputing.com>,
	Miguel Luis <miguel.luis@oracle.com>,
	James Morse <james.morse@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Oliver Upton <oliver.upton@linux.dev>,
	Zenghui Yu <yuzenghui@huawei.com>
Subject: [PATCH v3 26/27] KVM: arm64: Move HCRX_EL2 switch to load/put on VHE systems
Date: Tue,  8 Aug 2023 12:47:10 +0100	[thread overview]
Message-ID: <20230808114711.2013842-27-maz@kernel.org> (raw)
In-Reply-To: <20230808114711.2013842-1-maz@kernel.org>

Although the nVHE behaviour requires HCRX_EL2 to be switched
on each switch between host and guest, there is nothing in
this register that would affect a VHE host.

It is thus possible to save/restore this register on load/put
on VHE systems, avoiding unnecessary sysreg access on the hot
path. Additionally, it avoids unnecessary traps when running
with NV.

To achieve this, simply move the read/writes to the *_common()
helpers, which are called on load/put on VHE, and more eagerly
on nVHE.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/kvm/hyp/include/hyp/switch.h | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index a4750070563f..060c5a0409e5 100644
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -197,6 +197,9 @@ static inline void __activate_traps_common(struct kvm_vcpu *vcpu)
 	vcpu->arch.mdcr_el2_host = read_sysreg(mdcr_el2);
 	write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2);
 
+	if (cpus_have_final_cap(ARM64_HAS_HCX))
+		write_sysreg_s(HCRX_GUEST_FLAGS, SYS_HCRX_EL2);
+
 	__activate_traps_hfgxtr(vcpu);
 }
 
@@ -213,6 +216,9 @@ static inline void __deactivate_traps_common(struct kvm_vcpu *vcpu)
 		vcpu_clear_flag(vcpu, PMUSERENR_ON_CPU);
 	}
 
+	if (cpus_have_final_cap(ARM64_HAS_HCX))
+		write_sysreg_s(HCRX_HOST_FLAGS, SYS_HCRX_EL2);
+
 	__deactivate_traps_hfgxtr(vcpu);
 }
 
@@ -227,9 +233,6 @@ static inline void ___activate_traps(struct kvm_vcpu *vcpu)
 
 	if (cpus_have_final_cap(ARM64_HAS_RAS_EXTN) && (hcr & HCR_VSE))
 		write_sysreg_s(vcpu->arch.vsesr_el2, SYS_VSESR_EL2);
-
-	if (cpus_have_final_cap(ARM64_HAS_HCX))
-		write_sysreg_s(HCRX_GUEST_FLAGS, SYS_HCRX_EL2);
 }
 
 static inline void ___deactivate_traps(struct kvm_vcpu *vcpu)
@@ -244,9 +247,6 @@ static inline void ___deactivate_traps(struct kvm_vcpu *vcpu)
 		vcpu->arch.hcr_el2 &= ~HCR_VSE;
 		vcpu->arch.hcr_el2 |= read_sysreg(hcr_el2) & HCR_VSE;
 	}
-
-	if (cpus_have_final_cap(ARM64_HAS_HCX))
-		write_sysreg_s(HCRX_HOST_FLAGS, SYS_HCRX_EL2);
 }
 
 static inline bool __populate_fault_info(struct kvm_vcpu *vcpu)
-- 
2.34.1


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