linux-kernel - [PATCH v3 00/10] KVM: arm64: Avoid serializing LPI get() / put()

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Date: Fri, 16 Feb 2024 18:41:43 +0000
From: Oliver Upton <oliver.upton@...ux.dev>
To: kvmarm@...ts.linux.dev
Cc: kvm@...r.kernel.org,
	Marc Zyngier <maz@...nel.org>,
	James Morse <james.morse@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Zenghui Yu <yuzenghui@...wei.com>,
	linux-kernel@...r.kernel.org,
	Oliver Upton <oliver.upton@...ux.dev>
Subject: [PATCH v3 00/10] KVM: arm64: Avoid serializing LPI get() / put()

As discussed, here is a slimmed-down series for addressing lock
serialization in the vgic_get_irq() / vgic_put_irq() path for LPIs. The
bulk of it is using an xarray to represent LPIs and leveraging RCU to
avoid serializing readers of the LPI configuration state.

There's a lot of potential for clean-up, but this is intentionally
deferred until after we fix up the LPI translation cache.

v2: https://lore.kernel.org/kvmarm/20240213093250.3960069-1-oliver.upton@linux.dev/

v2 -> v3:
 - Fix the stupid lock imbalance once and for all (Dan)
 - Drop the tracepoints / stats I used for debugging my own crap (Marc)

Oliver Upton (10):
  KVM: arm64: vgic: Store LPIs in an xarray
  KVM: arm64: vgic: Use xarray to find LPI in vgic_get_lpi()
  KVM: arm64: vgic-v3: Iterate the xarray to find pending LPIs
  KVM: arm64: vgic-its: Walk the LPI xarray in vgic_copy_lpi_list()
  KVM: arm64: vgic: Get rid of the LPI linked-list
  KVM: arm64: vgic: Use atomics to count LPIs
  KVM: arm64: vgic: Free LPI vgic_irq structs in an RCU-safe manner
  KVM: arm64: vgic: Rely on RCU protection in vgic_get_lpi()
  KVM: arm64: vgic: Ensure the irq refcount is nonzero when taking a ref
  KVM: arm64: vgic: Don't acquire the lpi_list_lock in vgic_put_irq()

 arch/arm64/kvm/vgic/vgic-debug.c |  2 +-
 arch/arm64/kvm/vgic/vgic-init.c  |  4 ++-
 arch/arm64/kvm/vgic/vgic-its.c   | 53 +++++++++++++++++++-----------
 arch/arm64/kvm/vgic/vgic-v3.c    |  3 +-
 arch/arm64/kvm/vgic/vgic.c       | 56 ++++++++++----------------------
 arch/arm64/kvm/vgic/vgic.h       | 15 ++++++---
 include/kvm/arm_vgic.h           |  9 ++---
 7 files changed, 73 insertions(+), 69 deletions(-)


base-commit: 6613476e225e090cc9aad49be7fa504e290dd33d
-- 
2.44.0.rc0.258.g7320e95886-goog