[PATCH] KVM: ARM: ignore guest L2 cache control SMCs on Highbank and OMAP

[Rob Herring]

On Wed, Aug 14, 2013 at 4:22 AM, Andre Przywara
<andre.przywara at calxeda.com> wrote:
> Guest kernels with CONFIG_L2X0 set (for instance Highbank or OMAP4)
> will trigger SMCs to handle the L2 cache controller (PL310).
> This will currently inject #UNDEFs and eventually stop the guest.
>
> We don't need explicit L2 cache controller handling on A15s anymore,
> so it is safe to simply ignore these calls and proceed with the next
> instruction.
>
> Signed-off-by: Andre Przywara <andre.przywara at calxeda.com>
> ---
>  arch/arm/kvm/handle_exit.c | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)

At least for highbank, we can fix this in the kernel:

diff --git a/arch/arm/mach-highbank/highbank.c
b/arch/arm/mach-highbank/highbank.c
index 1894dcf..b5d0375 100644
--- a/arch/arm/mach-highbank/highbank.c
+++ b/arch/arm/mach-highbank/highbank.c
@@ -77,8 +77,10 @@ static void __init highbank_init_irq(void)
 {
        irqchip_init();

-       if (of_find_compatible_node(NULL, NULL, "arm,cortex-a9"))
-               highbank_scu_map_io();
+       if (!of_find_compatible_node(NULL, NULL, "arm,cortex-a9"))
+               return;
+
+       highbank_scu_map_io();

 #ifdef CONFIG_CACHE_L2X0
        /* Enable PL310 L2 Cache controller */

>
> diff --git a/arch/arm/kvm/handle_exit.c b/arch/arm/kvm/handle_exit.c
> index df4c82d..2cbe6a0 100644
> --- a/arch/arm/kvm/handle_exit.c
> +++ b/arch/arm/kvm/handle_exit.c
> @@ -50,8 +50,28 @@ static int handle_hvc(struct kvm_vcpu *vcpu, struct kvm_run *run)
>         return 1;
>  }
>
> +/*
> + * OMAP4 and Highbank machines do a SMC call to handle the L2 cache
> + * controller. They put 0x102 in r12 to request this functionality.
> + * This is not needed on A15s, so we can safely ignore it in KVM guests.
> + */
> +static int kvm_ignore_l2x0_call(struct kvm_vcpu *vcpu)
> +{
> +       unsigned long fn_nr = *vcpu_reg(vcpu, 12) & ~((u32) 0);
> +
> +       if (fn_nr == 0x102) {
> +               kvm_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(vcpu));
> +               return 1;
> +       }
> +
> +       return 0;
> +}
> +
>  static int handle_smc(struct kvm_vcpu *vcpu, struct kvm_run *run)
>  {
> +       if (kvm_ignore_l2x0_call(vcpu))
> +               return 1;
> +
>         kvm_inject_undefined(vcpu);
>         return 1;
>  }
> --
> 1.7.12.1
>
>
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