linux-kernel - [PATCH v10 00/18] KVM: arm64: Optimise FPSIMD context switching

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Date:   Tue, 22 May 2018 17:05:01 +0100
From:   Dave Martin <Dave.Martin@....com>
To:     kvmarm@...ts.cs.columbia.edu
Cc:     linux-arm-kernel@...ts.infradead.org,
        Christoffer Dall <cdall@...nel.org>,
        Marc Zyngier <marc.zyngier@....com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Oleg Nesterov <oleg@...hat.com>
Subject: [PATCH v10 00/18] KVM: arm64: Optimise FPSIMD context switching

Note: Most of these patches are Arm-specific.  People not Cc'd on the
whole series can find it in the linux-arm-kernel archive [2].

This series aims to improve the way FPSIMD context is handled by KVM.
Changes since the previous v9 [1] are mostly minor, but there are some
fixes worthy of closer attention.

In addition to addressing a review comment by Marc on the changes in v9,
this series attempts to fix a NULL-dereference bug observed by Marc on
ESPRESSOBin [5].  A reproducer for a similar bug is documented in [6],
and this series fixes the observed bug (in patches 1 and 7).  At the
moment, this is my best hypothesis for the ESPRESSOBin failure, though
the relationship is unproven and we have no reproducer for the latter.

The changes are summarised in the individual patches.

Reviewers please note:

 * Since v8, patches 10 and 14 have changed.  Reviewer tags have been
   stripped from patch 14, due to non-trivial changes in v9 of the
   series: see the patch for details.

 * Since v9, patches 1 and 7 are also new, and correct a latent bug in
   FPSIMD context handling which is exposed by this series.

If people could take a close look at the above patches, that would be
much appreciated.

Cheers
---Dave

[1] [PATCH v9 00/16] KVM: arm64: Optimise FPSIMD context switching
http://lists.infradead.org/pipermail/linux-arm-kernel/2018-May/579569.html

[2] linux-arm-kernel archive
http://lists.infradead.org/pipermail/linux-arm-kernel/2018-May/thread.html

[3] [kvmarm:queue 9/29] arch/arm/kvm/../../../virt/kvm/arm/arm.c:783:3: error: implicit declaration of function 'kvm_arch_vcpu_ctxsync_fp'; did you mean 'kvm_arch_vcpu_put_fp'?
http://lists.infradead.org/pipermail/linux-arm-kernel/2018-May/579400.html

[4] [kvmarm:queue 13/29] arch/arm/kvm/../../../virt/kvm/arm/arm.c:1598:6: error: implicit declaration of function 'system_supports_sve'
http://lists.infradead.org/pipermail/linux-arm-kernel/2018-May/579399.html

[5] [PULL v8] KVM: arm64: Optimise FPSIMD context switching
http://lists.infradead.org/pipermail/linux-arm-kernel/2018-May/579353.html


Christoffer Dall (1):
  KVM: arm/arm64: Introduce kvm_arch_vcpu_run_pid_change

Dave Martin (17):
  arm64: fpsimd: Fix TIF_FOREIGN_FPSTATE after invalidating cpu regs
  thread_info: Add update_thread_flag() helpers
  arm64: Use update{,_tsk}_thread_flag()
  KVM: arm64: Convert lazy FPSIMD context switch trap to C
  arm64: fpsimd: Generalise context saving for non-task contexts
  arm64: fpsimd: Eliminate task->mm checks
  arm64/sve: Refactor user SVE trap maintenance for external use
  KVM: arm64: Repurpose vcpu_arch.debug_flags for general-purpose flags
  KVM: arm64: Optimise FPSIMD handling to reduce guest/host thrashing
  arm64/sve: Move read_zcr_features() out of cpufeature.h
  arm64/sve: Switch sve_pffr() argument from task to thread
  arm64/sve: Move sve_pffr() to fpsimd.h and make inline
  KVM: arm64: Save host SVE context as appropriate
  KVM: arm64: Remove eager host SVE state saving
  KVM: arm64: Remove redundant *exit_code changes in fpsimd_guest_exit()
  KVM: arm64: Fold redundant exit code checks out of fixup_guest_exit()
  KVM: arm64: Invoke FPSIMD context switch trap from C

 arch/arm/include/asm/kvm_host.h      |  10 +-
 arch/arm64/Kconfig                   |   7 ++
 arch/arm64/include/asm/cpufeature.h  |  29 ------
 arch/arm64/include/asm/fpsimd.h      |  21 +++++
 arch/arm64/include/asm/kvm_asm.h     |   3 -
 arch/arm64/include/asm/kvm_host.h    |  45 +++++++--
 arch/arm64/include/asm/processor.h   |   2 +
 arch/arm64/include/asm/thread_info.h |   1 +
 arch/arm64/kernel/fpsimd.c           | 176 +++++++++++++++++------------------
 arch/arm64/kernel/ptrace.c           |   1 +
 arch/arm64/kvm/Kconfig               |   1 +
 arch/arm64/kvm/Makefile              |   2 +-
 arch/arm64/kvm/debug.c               |   8 +-
 arch/arm64/kvm/fpsimd.c              | 110 ++++++++++++++++++++++
 arch/arm64/kvm/hyp/debug-sr.c        |   6 +-
 arch/arm64/kvm/hyp/entry.S           |  43 ---------
 arch/arm64/kvm/hyp/hyp-entry.S       |  19 ----
 arch/arm64/kvm/hyp/switch.c          | 124 ++++++++++++++++--------
 arch/arm64/kvm/hyp/sysreg-sr.c       |   4 +-
 arch/arm64/kvm/sys_regs.c            |   9 +-
 include/linux/kvm_host.h             |   9 ++
 include/linux/sched.h                |   6 ++
 include/linux/thread_info.h          |  11 +++
 virt/kvm/Kconfig                     |   3 +
 virt/kvm/arm/arm.c                   |  14 ++-
 virt/kvm/kvm_main.c                  |   7 +-
 26 files changed, 416 insertions(+), 255 deletions(-)
 create mode 100644 arch/arm64/kvm/fpsimd.c

-- 
2.1.4