LCU14 BURLINGAME

C. Dall, M. Zyngier & E. Auger, LCU14

LCU14-506: KVM Development Status

● Finished “VM System Specification for ARM Processors”http://www.linaro.org/docs/vm-system-specification-arm-processors/

● BE/LE patches for KVM (Victor Kamensky)

● ARMv8-A Debug Patches (Marc Zyngier)

● Fixes 64K Pages

KVM for ARM/ARM64 - Since Last

● Read-Only Memory Regions (Christoffer Dall, in kvmarm/next)● VTTBR_MASK (Joel Schopp)

● VGIC cleanup series (Christoffer Dall)

● Dynamic VGIC sizing series (Marc Zyngier)

● GICv3 emulation series (Andre Przywara)

● ARMv8 PMU Support Series (Anup Patel)

● Forwarding physical interrupts series (Marc Zyngier)

● IRQFD patch series (Eric Auger)

● KVM-VFIO IRQ Forward Control (Eric Auger)

In flight

● Currently only addresses the VTTBR_MASK

● We need a proper flexible solution that allows user space to discover the physical address size capabilities of the host

● Policy decision on concatenated first-level stage-2 page tables

● Dynamic size allocation of first-level stage-2 page tables

● Decoupling kernel and KVM page table manipulation functions?

VTTBR_MASK Fixes

● Cleanup: Need to sort out a few minor things● Likely to go in for v3.18

● Dynamic sizing: v3 is out with comments, awaiting new version

● GICv3: Awaiting more review and depends on above

VGIC Patches

● RFC Out with comments, awaiting new version

● Any issues to discuss at this forum?

ARMv8 PMU Support

● irqchip only drops priority on interrupt during EOI (no deactivate)● irqchip provides methods to save/restore interrupt state

● VGIC Sets the LR.HW bit

● VM deactivates interrupt when EOI virtual interrupt

● Active State is part of the Generic Timers state● (Avoids the need for the hypervisor to set CNTV_CTL.IMASK)

● Other use case is VFIO

● Initial patch series is on the list

IRQ Forwarding

● Allows to register a (eventfd, gsi, VM) triplet to KVM: ● when the eventfd is triggered, KVM injects the gsi (virtual IRQ) into the VM

● Virtual IRQ completion is trapped at VGIC level and VGIC supportstriggering a resamplefd on level-triggered EOI

● No GSI routing enabled anymore

● Do we need to support PPI passthrough?

● Use cases in VFIO and vhost-net

● v3 of patch series for ARM is on the list

IRQFD

● Enables VFIO device IRQ forwarding

● KVM-VFIO device programs IRQCHIP, VGIC and VFIO:● IRQ de-activation performed by guest● disable IRQ masking at VFIO driver● Program GICH_LR with HW bit and IRQ

number (no maintenance IRQ)

● RFC v2 is on the list

KVM-VFIO

Kernel

User Space Process

VFIO irqchip KVM

● Ard Biesheuvel has ported UEFI to QEMU’s ARMv8 “virt” platform● Tested with KVM as well● Being reviewed upstream (at time of writing)

● Some changes required to QEMU, patches on the list

● Remaining work is tracked in CARD-1535

UEFI (Image Spec Compliance)

● Some load/store instructions (writeback or ldm/stm, ldp/stp) provide invalid ESR_EL2.ISS

● KVM must decode the instructions to determine:● Load or Store● Size of access (byte, halfword, word, multiple words)● Registers used● Side effects (write-back)

● Old patches with reviewed-by tags did not make it upstream

● Causes UEFI to fail on aarch64

● Time to revive patches?

Instruction Decoding

● Discussions

● Suggestions

● Questions

Open Floor

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