linux-kernel - [RFC 0/4] arm64: kexec: fix kvm issue in kexec

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Date:	Mon, 23 Mar 2015 20:53:55 +0900
From:	AKASHI Takahiro <takahiro.akashi@...aro.org>
To:	catalin.marinas@....com, will.deacon@....com, marc.zyngier@....com,
	mark.rutland@....com
Cc:	christoffer.dall@...aro.org, geoff@...radead.org,
	broonie@...nel.org, david.griego@...aro.org, freddy77@...il.com,
	kexec@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org,
	linaro-kernel@...ts.linaro.org, linux-kernel@...r.kernel.org,
	AKASHI Takahiro <takahiro.akashi@...aro.org>
Subject: [RFC 0/4] arm64: kexec: fix kvm issue in kexec

This patch set addresses KVM issue described in Geoff's kexec patch set.
    http://lists.infradead.org/pipermail/kexec/2015-March/013432.html

The basic approach here is to define a kvm tear-down function and add
a reboot hook to gracefully shutdown the 1st kernel. This way, kvm gets
free from kexec-specific cleanup and yet we allows future enhancement,
like cpu hotplug & building kvm as a module, based on tear-down function.
In this sense, patch #1 & #2 actually fix the problem, and #3 & #4 are
rather informative.

I confirmed that 1st kernel successfully shut down and 2nd kernel started
with the following messages:

    kvm [1]: Using HYP init bounce page @8fa52f000
    kvm [1]: interrupt-controller@...2f000 IRQ6
    kvm [1]: timer IRQ3
    kvm [1]: Hyp mode initialized successfully

test target: Base fast model
version:     kernel v4.0-rc4 + Geoff's kexec v8

I still have some concerns about the following points. Please let me know
if you have any comments:

1) Call kvm_cpu_reset() on non-boot cpus in reboot notifier
   We don't have to do so in kexec-specific case. But the current code runs
   the function on each cpu for safety since we use a general reboot hook.
2) Flush D$ in kvm_cpu_reset()
   Currently doesn't do so because all the cpus are just going to shut down,
   and we actually flush D$ on boot cpu in Geoff's cpu_reset().
3) Compatibility with arm implementation
   Frediano is no longer working on this issue on arm as he left his
   company. But my approach here is based on a generic interface and can be
   applied to arm in a similar way.

   http://lists.infradead.org/pipermail/linux-arm-kernel/2015-February/322231.html

AKASHI Takahiro (4):
  arm64: kvm: add a cpu tear-down function
  arm64: kexec: fix kvm issue
  arm64: kvm: add cpu reset hook for cpu hotplug
  arm64: kvm: add cpu reset at module exit

 arch/arm/kvm/arm.c                |   54 +++++++++++++++++++++++++++++++++++++
 arch/arm/kvm/mmu.c                |   16 +++++++++++
 arch/arm64/include/asm/kvm_asm.h  |    3 +++
 arch/arm64/include/asm/kvm_host.h |   11 +++++++-
 arch/arm64/include/asm/kvm_mmu.h  |    3 +++
 arch/arm64/include/asm/virt.h     |   11 ++++++++
 arch/arm64/kvm/Kconfig            |    1 -
 arch/arm64/kvm/hyp-init.S         |   41 ++++++++++++++++++++++++++++
 arch/arm64/kvm/hyp.S              |   29 +++++++++++++++++---
 9 files changed, 163 insertions(+), 6 deletions(-)

-- 
1.7.9.5

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