linux-kernel - [PATCH 5.15 v2 09/10] KVM: arm64: Calculate cptr

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Message-Id: <20250403-stable-sve-5-15-v2-9-30a36a78a20a@kernel.org>
Date: Thu, 03 Apr 2025 00:20:24 +0100
From: Mark Brown <broonie@...nel.org>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 Marc Zyngier <maz@...nel.org>, James Morse <james.morse@....com>, 
 Suzuki K Poulose <suzuki.poulose@....com>, 
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, 
 Oleg Nesterov <oleg@...hat.com>, Oliver Upton <oliver.upton@...ux.dev>
Cc: linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu, 
 linux-kernel@...r.kernel.org, stable@...r.kernel.org, 
 Mark Brown <broonie@...nel.org>, Fuad Tabba <tabba@...gle.com>, 
 James Clark <james.clark@...aro.org>
Subject: [PATCH 5.15 v2 09/10] KVM: arm64: Calculate cptr_el2 traps on
 activating traps

From: Fuad Tabba <tabba@...gle.com>

[ Upstream commit 2fd5b4b0e7b440602455b79977bfa64dea101e6c ]

Similar to VHE, calculate the value of cptr_el2 from scratch on
activate traps. This removes the need to store cptr_el2 in every
vcpu structure. Moreover, some traps, such as whether the guest
owns the fp registers, need to be set on every vcpu run.

Reported-by: James Clark <james.clark@...aro.org>
Fixes: 5294afdbf45a ("KVM: arm64: Exclude FP ownership from kvm_vcpu_arch")
Signed-off-by: Fuad Tabba <tabba@...gle.com>
Link: https://lore.kernel.org/r/20241216105057.579031-13-tabba@google.com
Signed-off-by: Marc Zyngier <maz@...nel.org>
Signed-off-by: Mark Brown <broonie@...nel.org>
---
 arch/arm64/include/asm/kvm_host.h |  1 -
 arch/arm64/kvm/arm.c              |  1 -
 arch/arm64/kvm/hyp/nvhe/switch.c  | 35 ++++++++++++++++++++++++++---------
 3 files changed, 26 insertions(+), 11 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 3d4e2396a2d7..2e0952134e2e 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -301,7 +301,6 @@ struct kvm_vcpu_arch {
 	/* Values of trap registers for the guest. */
 	u64 hcr_el2;
 	u64 mdcr_el2;
-	u64 cptr_el2;
 
 	/* Values of trap registers for the host before guest entry. */
 	u64 mdcr_el2_host;
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 9ded5443de48..5ca8782edb96 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1138,7 +1138,6 @@ static int kvm_arch_vcpu_ioctl_vcpu_init(struct kvm_vcpu *vcpu,
 	}
 
 	vcpu_reset_hcr(vcpu);
-	vcpu->arch.cptr_el2 = CPTR_EL2_DEFAULT;
 
 	/*
 	 * Handle the "start in power-off" case.
diff --git a/arch/arm64/kvm/hyp/nvhe/switch.c b/arch/arm64/kvm/hyp/nvhe/switch.c
index 4db5409f40c4..c0885197f2a5 100644
--- a/arch/arm64/kvm/hyp/nvhe/switch.c
+++ b/arch/arm64/kvm/hyp/nvhe/switch.c
@@ -34,21 +34,38 @@ DEFINE_PER_CPU(struct kvm_host_data, kvm_host_data);
 DEFINE_PER_CPU(struct kvm_cpu_context, kvm_hyp_ctxt);
 DEFINE_PER_CPU(unsigned long, kvm_hyp_vector);
 
-static void __activate_traps(struct kvm_vcpu *vcpu)
+static bool guest_owns_fp_regs(struct kvm_vcpu *vcpu)
 {
-	u64 val;
+	return vcpu->arch.flags & KVM_ARM64_FP_ENABLED;
+}
 
-	___activate_traps(vcpu);
-	__activate_traps_common(vcpu);
+static void __activate_cptr_traps(struct kvm_vcpu *vcpu)
+{
+	u64 val = CPTR_EL2_TAM;	/* Same bit irrespective of E2H */
 
-	val = vcpu->arch.cptr_el2;
-	val |= CPTR_EL2_TTA | CPTR_EL2_TAM;
-	if (!update_fp_enabled(vcpu)) {
-		val |= CPTR_EL2_TFP | CPTR_EL2_TZ;
-		__activate_traps_fpsimd32(vcpu);
+	/* !hVHE case upstream */
+	if (1) {
+		val |= CPTR_EL2_TTA | CPTR_NVHE_EL2_RES1;
+
+		if (!vcpu_has_sve(vcpu) || !guest_owns_fp_regs(vcpu))
+			val |= CPTR_EL2_TZ;
+
+		if (!guest_owns_fp_regs(vcpu))
+			val |= CPTR_EL2_TFP;
 	}
 
+	if (!guest_owns_fp_regs(vcpu))
+		__activate_traps_fpsimd32(vcpu);
+
 	write_sysreg(val, cptr_el2);
+}
+
+static void __activate_traps(struct kvm_vcpu *vcpu)
+{
+	___activate_traps(vcpu);
+	__activate_traps_common(vcpu);
+	__activate_cptr_traps(vcpu);
+
 	write_sysreg(__this_cpu_read(kvm_hyp_vector), vbar_el2);
 
 	if (cpus_have_final_cap(ARM64_WORKAROUND_SPECULATIVE_AT)) {

-- 
2.39.5