[PATCH] arm/arm64: KVM: detect CPU reset on CPU_PM_EXIT
Christoffer Dall
christoffer.dall at linaro.org
Thu Feb 20 20:23:58 EST 2014
On Thu, Feb 20, 2014 at 03:26:54PM +0000, Marc Zyngier wrote:
> Commit 1fcf7ce0c602 (arm: kvm: implement CPU PM notifier) added
> support for CPU power-management, using a cpu_nofigier to re-init
> KVM on a CPU that entered CPU idle.
>
> The code assumed that a CPU entering idle would actually be powered
> off, loosing its state entierely, and would then need to be
> reinitialized. It turns out that this is not always the case, and
> some HW performs CPU PM without actually killing the core. In this
> case, we try to reinitialize KVM while it still live. It ends up
> badly, as reported by Andre Przywara (using a Calxeda Midway):
>
> [ 3.663897] Kernel panic - not syncing: unexpected prefetch abort in Hyp mode at: 0x685760
> [ 3.663897] unexpected data abort in Hyp mode at: 0xc067d150
> [ 3.663897] unexpected HVC/SVC trap in Hyp mode at: 0xc0901dd0
>
> The trick here is to detect if we've been through a full re-init or
> not by looking at HVBAR (VBAR_EL2 on arm64). This involves
> implementing the backend for __hyp_get_vectors in the main KVM HYP
> code (rather small), and checking the return value against the
> default one when the CPU notifier is called on CPU_PM_EXIT.
This definitely looks correct and is a good solution, so
Acked-by: Christoffer Dall <christoffer.dall at linaro.org>
But see my usual request below.
>
> Reported-by: Andre Przywara <osp at andrep.de>
> Cc: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
> Cc: Rob Herring <rob.herring at linaro.org>
> Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>
> ---
> arch/arm/kvm/arm.c | 3 ++-
> arch/arm/kvm/interrupts.S | 7 ++++++-
> arch/arm64/kvm/hyp.S | 9 +++++++--
> 3 files changed, 15 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index 1d8248e..bd18bb8 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -878,7 +878,8 @@ static int hyp_init_cpu_pm_notifier(struct notifier_block *self,
> unsigned long cmd,
> void *v)
> {
> - if (cmd == CPU_PM_EXIT) {
> + if (cmd == CPU_PM_EXIT &&
> + __hyp_get_vectors() == hyp_default_vectors) {
> cpu_init_hyp_mode(NULL);
> return NOTIFY_OK;
> }
> diff --git a/arch/arm/kvm/interrupts.S b/arch/arm/kvm/interrupts.S
> index ddc1553..9b0ff68 100644
> --- a/arch/arm/kvm/interrupts.S
> +++ b/arch/arm/kvm/interrupts.S
> @@ -363,6 +363,11 @@ hyp_hvc:
> host_switch_to_hyp:
> pop {r0, r1, r2}
>
> + /* Check for __hyp_get_vectors */
> + cmp r0, #-1
> + mrceq p15, 4, r0, c12, c0, 0 @ get HVBAR
> + beq 1f
> +
I hate to be a stickler about this, but I think the comment explaining
the KVM/ARM Hypervisor ABI needs to be tweaked (it may have been too
verbose to begin with), but it should be updated at least to specify the
special-case handling of r0. I think a small comment somewhere on the
arm64 part would be similarly nice, but it's not something that should
hold this patch back.
> push {lr}
> mrs lr, SPSR
> push {lr}
> @@ -378,7 +383,7 @@ THUMB( orr lr, #1)
> pop {lr}
> msr SPSR_csxf, lr
> pop {lr}
> - eret
> +1: eret
>
> guest_trap:
> load_vcpu @ Load VCPU pointer to r0
> diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S
> index 3b47c36..f1cbabe 100644
> --- a/arch/arm64/kvm/hyp.S
> +++ b/arch/arm64/kvm/hyp.S
> @@ -737,7 +737,12 @@ el1_sync: // Guest trapped into EL2
> pop x2, x3
> pop x0, x1
>
> - push lr, xzr
> + /* Check for __hyp_get_vectors */
> + cbnz x0, 1f
> + mrs x0, vbar_el2
> + b 2f
> +
> +1: push lr, xzr
>
> /*
> * Compute the function address in EL2, and shuffle the parameters.
> @@ -750,7 +755,7 @@ el1_sync: // Guest trapped into EL2
> blr lr
>
> pop lr, xzr
> - eret
> +2: eret
>
> el1_trap:
> /*
> --
> 1.8.3.4
>
Thanks,
--
Christoffer
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