[v3 0/5] arm64: kvm: reset hyp context for kexec

AKASHI Takahiro
2015-04-02T05:40:45Z

This patch set addresses KVM issue described in Geoff's kexec patch set[1].
(The subject was changed from "arm64: kexec: fix kvm issue in kexec.")
See "Changes" below.

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 (and #5) 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@2c02f000 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 + Arn's patch[2]

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[2] 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.

Changes from v2:
* modified kvm_virt_to_trampoline() macro to fix a page-alignment issue[4]

Changes from v1:
* modified kvm_cpu_reset() implementation:
- define a macro to translate va to addr in trampoline
- use __hyp_default_vectors instead of kvm_get_hyp_stub_vectors()
- shuffle the arguments in __cpu_reset_hyp_mode()
- optimize TLB flush operations
* changed a patch#2's name
* added a patch#5 to add stub code for arm

[1] http://lists.infradead.org/pipermail/kexec/2015-March/013432.html
[2] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-March/334002.html
[3] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-February/322231.html
[4] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-March/334910.html

AKASHI Takahiro (5):
arm64: kvm: add a cpu tear-down function
arm64: kvm: allow EL2 context to be reset on shutdown
arm64: kvm: add cpu reset hook for cpu hotplug
arm64: kvm: add cpu reset at module exit
arm: kvm: add stub implementation for kvm_cpu_reset()

arch/arm/include/asm/kvm_asm.h | 1 +
arch/arm/include/asm/kvm_host.h | 13 +++++++++-
arch/arm/include/asm/kvm_mmu.h | 5 ++++
arch/arm/kvm/arm.c | 51 +++++++++++++++++++++++++++++++++++++
arch/arm/kvm/init.S | 6 +++++
arch/arm/kvm/mmu.c | 5 ++++
arch/arm64/include/asm/kvm_asm.h | 1 +
arch/arm64/include/asm/kvm_host.h | 12 ++++++++-
arch/arm64/include/asm/kvm_mmu.h | 7 +++++
arch/arm64/include/asm/virt.h | 11 ++++++++
arch/arm64/kvm/Kconfig | 1 -
arch/arm64/kvm/hyp-init.S | 35 +++++++++++++++++++++++++
arch/arm64/kvm/hyp.S | 16 +++++++++---
13 files changed, 158 insertions(+), 6 deletions(-)

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1.7.9.5