[PATCH v5 11/15] KVM: arm64: Reserve dirty ring space for the HDBSS buffer
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COOLING7d
From: Tian Zheng <hidden>
Date: 2026-09-29 10:37:13
Also in:
kvm, kvmarm, linux-doc, linux-kselftest, lkml
Subsystem:
arm64 port (aarch64 architecture), kernel virtual machine for arm64 (kvm/arm64), the rest · Maintainers:
Catalin Marinas, Will Deacon, Marc Zyngier, Oliver Upton, Linus Torvalds
The dirty ring reserves room for CPU-side dirty buffers via kvm_cpu_dirty_log_size(). Report the HDBSS buffer entry count through it, so a full buffer flush always fits in the ring. Pin the HDBSS buffer size to PAGE_SIZE when dirty-ring is enabled, via kvm_arch_dirty_ring_size_updated(): a larger buffer only shrinks the soft_limit and forces more frequent userspace drains. Signed-off-by: Tian Zheng <redacted> --- arch/arm64/kvm/arm.c | 8 ++++++++ arch/arm64/kvm/mmu.c | 8 ++++++++ 2 files changed, 16 insertions(+)
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 9d7bdece149a..5a7046acb62e 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c@@ -215,6 +215,14 @@ static int kvm_arm_default_max_vcpus(void) return vgic_present ? kvm_vgic_get_max_vcpus() : KVM_MAX_VCPUS; } +void kvm_arch_dirty_ring_size_updated(struct kvm *kvm) +{ + if (!system_supports_hdbss()) + return; + + kvm->arch.hdbss_buffer_size = KVM_ARM_HDBSS_DEFAULT_SIZE; +} + /** * kvm_arch_init_vm - initializes a VM data structure * @kvm: pointer to the KVM struct
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 7bf82d65041c..c1e09ba98d48 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c@@ -2841,3 +2841,11 @@ void kvm_toggle_cache(struct kvm_vcpu *vcpu, bool was_enabled) trace_kvm_toggle_cache(*vcpu_pc(vcpu), was_enabled, now_enabled); } + +int kvm_cpu_dirty_log_size(struct kvm *kvm) +{ + if (!system_supports_hdbss()) + return 0; + + return kvm_hdbss_buffer_size(kvm) / sizeof(u64); +} --
2.43.0