Patch "KVM: arm64: Calculate cptr_el2 traps on activating traps" has been added to the 5.15-stable tree

Mon Apr 21 23:45:13 PDT 2025

This is a note to let you know that I've just added the patch titled

    KVM: arm64: Calculate cptr_el2 traps on activating traps

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     kvm-arm64-calculate-cptr_el2-traps-on-activating-traps.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable at vger.kernel.org> know about it.


>From broonie at kernel.org Tue Apr  8 20:22:50 2025
From: Mark Brown <broonie at kernel.org>
Date: Tue, 08 Apr 2025 19:10:05 +0100
Subject: KVM: arm64: Calculate cptr_el2 traps on activating traps
To: Greg Kroah-Hartman <gregkh at linuxfoundation.org>,  Marc Zyngier <maz at kernel.org>, James Morse <james.morse at arm.com>,  Suzuki K Poulose <suzuki.poulose at arm.com>,  Catalin Marinas <catalin.marinas at arm.com>, Will Deacon <will at kernel.org>,  Oleg Nesterov <oleg at redhat.com>, Oliver Upton <oliver.upton at linux.dev>
Cc: linux-arm-kernel at lists.infradead.org, kvmarm at lists.cs.columbia.edu,  linux-kernel at vger.kernel.org, stable at vger.kernel.org,  Mark Brown <broonie at kernel.org>, Fuad Tabba <tabba at google.com>,  James Clark <james.clark at linaro.org>
Message-ID: <20250408-stable-sve-5-15-v3-10-ca9a6b850f55 at kernel.org>

From: Fuad Tabba <tabba at google.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 at linaro.org>
Fixes: 5294afdbf45a ("KVM: arm64: Exclude FP ownership from kvm_vcpu_arch")
Signed-off-by: Fuad Tabba <tabba at google.com>
Link: https://lore.kernel.org/r/20241216105057.579031-13-tabba@google.com
Signed-off-by: Marc Zyngier <maz at kernel.org>
Signed-off-by: Mark Brown <broonie at kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.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(-)

--- 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;
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1138,7 +1138,6 @@ static int kvm_arch_vcpu_ioctl_vcpu_init
 	}
 
 	vcpu_reset_hcr(vcpu);
-	vcpu->arch.cptr_el2 = CPTR_EL2_DEFAULT;
 
 	/*
 	 * Handle the "start in power-off" case.
--- 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
 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)) {


Patches currently in stable-queue which might be from broonie at kernel.org are

queue-5.15/kvm-arm64-remove-host-fpsimd-saving-for-non-protected-kvm.patch
queue-5.15/spi-cadence-qspi-fix-probe-on-am62a-lp-sk.patch
queue-5.15/asoc-qdsp6-q6asm-dai-fix-q6asm_dai_compr_set_params-error-path.patch
queue-5.15/kvm-arm64-eagerly-switch-zcr_el-1-2.patch
queue-5.15/kvm-arm64-unconditionally-save-flush-host-fpsimd-sve-sme-state.patch
queue-5.15/kvm-arm64-always-start-with-clearing-sve-flag-on-load.patch
queue-5.15/asoc-codecs-lpass-wsa-macro-fix-vi-feedback-rate.patch
queue-5.15/arm64-fpsimd-track-the-saved-fpsimd-state-type-separately-to-tif_sve.patch
queue-5.15/kvm-arm64-get-rid-of-host-sve-tracking-saving.patch
queue-5.15/kvm-arm64-remove-vhe-host-restore-of-cpacr_el1.zen.patch
queue-5.15/asoc-fsl_audmix-register-card-device-depends-on-dais.patch
queue-5.15/arm64-fpsimd-have-kvm-explicitly-say-which-fp-registers-to-save.patch
queue-5.15/kvm-arm64-discard-any-sve-state-when-entering-kvm-guests.patch
queue-5.15/arm64-fpsimd-stop-using-tif_sve-to-manage-register-saving-in-kvm.patch
queue-5.15/asoc-codecs-lpass-wsa-macro-fix-logic-of-enabling-vi-channels.patch
queue-5.15/kvm-arm64-calculate-cptr_el2-traps-on-activating-traps.patch

