Re: [PATCH v3 0/3] arm/arm64: KVM: Random selection of cache related fixes

[Andrew Jones <drjones@redhat.com>]

On Wed, Jan 21, 2015 at 06:39:45PM +0000, Marc Zyngier wrote:
> This small series fixes a number of issues that Christoffer and I have
> been trying to nail down for a while, having to do with the host dying
> under load (swapping), and also with the way we deal with caches in
> general (and with set/way operation in particular):
> 
> - The first one changes the way we handle cache ops by set/way,
>   basically turning them into VA ops for the whole memory. This allows
>   platforms with system caches to boot a 32bit zImage, for example.
> 
> - The second one fixes a corner case that could happen if the guest
>   used an uncached mapping (or had its caches off) while the host was
>   swapping it out (and using a cache-coherent IO subsystem).
> 
> - Finally, the last one fixes this stability issue when the host was
>   swapping, by using a kernel mapping for cache maintenance instead of
>   the userspace one.
> 
> With these patches (and both the TLB invalidation and HCR fixes that
> are on their way to mainline), the APM platform seems much more robust
> than it previously was. Fingers crossed.
> 
> The first round of review has generated a lot of traffic about
> ASID-tagged icache management for guests, but I've decided not to
> address this issue as part of this series. The code is broken already,
> and there isn't any virtualization capable, ASID-tagged icache core in
> the wild, AFAIK. I'll try to revisit this in another series, once I
> have wrapped my head around it (or someone beats me to it).
> 
> Based on 3.19-rc5, tested on Juno, X-Gene, TC-2 and Cubietruck.
> 
> Also at git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git kvm-arm64/mm-fixes-3.19
> 
> * From v2: [2]
> - Reworked the algorithm that tracks the state of the guest's caches,
>   as there is some cases I didn't anticipate. In the end, the
>   algorithm is simpler.
> 
> * From v1: [1]
> - Dropped Steve's patch after discussion with Andrea
> - Refactor set/way support to avoid code duplication, better comments
> - Much improved comments in patch #2, courtesy of Christoffer
> 
> [1]: http://www.spinics.net/lists/kvm-arm/msg13008.html
> [2]: http://www.spinics.net/lists/kvm-arm/msg13161.html
> 
> Marc Zyngier (3):
>   arm/arm64: KVM: Use set/way op trapping to track the state of the
>     caches
>   arm/arm64: KVM: Invalidate data cache on unmap
>   arm/arm64: KVM: Use kernel mapping to perform invalidation on page
>     fault
> 
>  arch/arm/include/asm/kvm_emulate.h   |  10 +++
>  arch/arm/include/asm/kvm_host.h      |   3 -
>  arch/arm/include/asm/kvm_mmu.h       |  77 +++++++++++++---
>  arch/arm/kvm/arm.c                   |  10 ---
>  arch/arm/kvm/coproc.c                |  64 +++-----------
>  arch/arm/kvm/coproc_a15.c            |   2 +-
>  arch/arm/kvm/coproc_a7.c             |   2 +-
>  arch/arm/kvm/mmu.c                   | 164 ++++++++++++++++++++++++++++++-----
>  arch/arm/kvm/trace.h                 |  39 +++++++++
>  arch/arm64/include/asm/kvm_emulate.h |  10 +++
>  arch/arm64/include/asm/kvm_host.h    |   3 -
>  arch/arm64/include/asm/kvm_mmu.h     |  34 ++++++--
>  arch/arm64/kvm/sys_regs.c            |  75 +++-------------
>  13 files changed, 321 insertions(+), 172 deletions(-)
> 
> -- 
> 2.1.4
> 
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Hi Marc,

checkpatch found some whitespace issues (not just the false alarms
that trace.h files generate). Also a loosing vs. losing typo in 2/3's
commit message.

Thanks,
Drew (trivial comments) Jones