RE: [PATCH v2 0/3] kvm/arm: New VMID allocator based on asid

Shameerali Kolothum Thodi
2021-07-13T07:07:29Z

Hi Marc,

> -----Original Message-----
> From: Shameerali Kolothum Thodi
> Sent: 16 June 2021 16:56
> To: linux-arm-kernel@lists.infradead.org; kvmarm@lists.cs.columbia.edu;
> linux-kernel@vger.kernel.org
> Cc: maz@kernel.org; will@kernel.org; catalin.marinas@arm.com;
> james.morse@arm.com; julien.thierry.kdev@gmail.com;
> suzuki.poulose@arm.com; jean-philippe@linaro.org;
> Alexandru.Elisei@arm.com; Linuxarm <linuxarm@huawei.com>
> Subject: [PATCH v2 0/3] kvm/arm: New VMID allocator based on asid
>
> Hi,
>
> RFCv1 --> v2
> - Dropped "pinned VMID" support for now.
> - Dropped RFC tag.
>
> Sanity tested on HiSilicon D06 board.

A gentle ping on this one. Please let me know if you had a chance to look
at this and have any feedback. I could do a rebase to 5.14-rc1 if required.

Thanks,
Shameer

>
> Thanks,
> Shameer
>
> History:
> -------
> Please find the RFC series here,
> https://lore.kernel.org/kvmarm/20210506165232.1969-1-shameerali.kolothu
> m.thodi@huawei.com/
>
> From RFCv1:
>
> This is based on a suggestion from Will [0] to try out the asid
> based kvm vmid solution as a separate VMID allocator instead of
> the shared lib approach attempted in v4[1].
>
> The idea is to compare both the approaches and see whether the
> shared lib solution with callbacks make sense or not.
>
> Though we are not using the pinned vmids yet, patch #2 has
> code for pinned vmid support. This is just to help the comparison.
>
> Test Setup/Results
> ----------------
> The measurement was made with maxcpus set to 8 and with the
> number of VMID limited to 4-bit. The test involves running
> concurrently 40 guests with 2 vCPUs. Each guest will then
> execute hackbench 5 times before exiting.
>
> The performance difference between the current algo and the
> new one are(avg. of 10 runs):
> - 1.9% less entry/exit from the guest
> - 0.5% faster
>
> This is more or less comparable to v4 numbers.
>
> For the complete series, please see,
> https://github.com/hisilicon/kernel-dev/tree/private-v5.12-rc7-vmid-2nd-rfc
>
> and for the shared asid lib v4 solution,
> https://github.com/hisilicon/kernel-dev/tree/private-v5.12-rc7-asid-v4
>
> As you can see there are ofcourse code duplication with this
> approach but may be it is more easy to maintain considering
> the complexity involved.
>
> [0] https://lore.kernel.org/lkml/20210422160846.GB2214@willie-the-truck/
> [1]
> https://lore.kernel.org/lkml/20210414112312.13704-1-shameerali.kolothum.t
> hodi@huawei.com/
>
> Julien Grall (2):
> arch/arm64: Introduce a capability to tell whether 16-bit VMID is
> available
> kvm/arm: Align the VMID allocation with the arm64 ASID one
>
> Shameer Kolothum (1):
> kvm/arm: Introduce a new vmid allocator for KVM
>
> arch/arm64/include/asm/kvm_asm.h | 4 +-
> arch/arm64/include/asm/kvm_host.h | 10 +-
> arch/arm64/include/asm/kvm_mmu.h | 7 +-
> arch/arm64/kernel/cpufeature.c | 9 ++
> arch/arm64/kvm/Makefile | 2 +-
> arch/arm64/kvm/arm.c | 115 ++++----------
> arch/arm64/kvm/hyp/nvhe/hyp-main.c | 6 +-
> arch/arm64/kvm/hyp/nvhe/mem_protect.c | 3 +-
> arch/arm64/kvm/hyp/nvhe/tlb.c | 10 +-
> arch/arm64/kvm/hyp/vhe/tlb.c | 10 +-
> arch/arm64/kvm/mmu.c | 1 -
> arch/arm64/kvm/vmid.c | 206
> ++++++++++++++++++++++++++
> arch/arm64/tools/cpucaps | 1 +
> 13 files changed, 273 insertions(+), 111 deletions(-)
> create mode 100644 arch/arm64/kvm/vmid.c
>
> --
> 2.17.1