linux-kernel - [PATCH v2 0/2] KVM: arm64: Optimize the wait for the completion of the VPT analysis

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:   Sat, 28 Nov 2020 22:18:55 +0800
From:   Shenming Lu <lushenming@...wei.com>
To:     Marc Zyngier <maz@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Jason Cooper" <jason@...edaemon.net>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <kvmarm@...ts.cs.columbia.edu>, <kvm@...r.kernel.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Eric Auger <eric.auger@...hat.com>,
        Christoffer Dall <christoffer.dall@....com>
CC:     <wanghaibin.wang@...wei.com>, <yuzenghui@...wei.com>,
        <lushenming@...wei.com>
Subject: [PATCH v2 0/2] KVM: arm64: Optimize the wait for the completion of the VPT analysis

Right after a vPE is made resident, the code starts polling the
GICR_VPENDBASER.Dirty bit until it becomes 0, where the delay_us
is set to 10. But in our measurement, it takes only hundreds of
nanoseconds, or 1~2 microseconds, to finish parsing the VPT in most
cases. What's more, we found that the MMIO delay on GICv4.1 system
(HiSilicon) is about 10 times higher than that on GICv4.0 system in
kvm-unit-tests (the specific data is as follows).

                        |   GICv4.1 emulator   |  GICv4.0 emulator
mmio_read_user (ns)     |        12811         |        1598

After analysis, this is mainly caused by the 10 delay_us, so it might
really hurt performance.

To avoid this, we can set the delay_us to 1, which is more appropriate
in this situation and universal. Besides, we can delay the execution
of the polling, giving the GIC a chance to work in parallel with the CPU
on the entry path.

Shenming Lu (2):
  irqchip/gic-v4.1: Reduce the delay time of the poll on the
    GICR_VPENDBASER.Dirty bit
  KVM: arm64: Delay the execution of the polling on the
    GICR_VPENDBASER.Dirty bit

 arch/arm64/kvm/vgic/vgic-v4.c      | 16 ++++++++++++++++
 arch/arm64/kvm/vgic/vgic.c         |  3 +++
 drivers/irqchip/irq-gic-v3-its.c   | 18 +++++++++++++-----
 drivers/irqchip/irq-gic-v4.c       | 11 +++++++++++
 include/kvm/arm_vgic.h             |  3 +++
 include/linux/irqchip/arm-gic-v4.h |  4 ++++
 6 files changed, 50 insertions(+), 5 deletions(-)

-- 
2.23.0