On Mon, Feb 20, 2017 at 12:30:12PM +0000, Mark Rutland wrote:
> Currently we BUG() if we see an ESR_EL2.EC value we don't recognise. As
> configurable disables/enables are added to the architecture (controlled
> by RES1/RES0 bits respectively), with associated synchronous exceptions,
> it may be possible for a guest to trigger exceptions with classes that
> we don't recognise.
>
> While we can't service these exceptions in a manner useful to the guest,
> we can avoid bringing down the host. Per ARM DDI 0487A.k_iss10775, page
> D7-1937, EC values within the range 0x00 - 0x2c are reserved for future
> use with synchronous exceptions, and EC values within the range 0x2d -
> 0x3f may be used for either synchronous or asynchronous exceptions.
>
> The patch makes KVM handle any unknown EC by injecting an UNDEFINED
> exception into the guest, with a corresponding (ratelimited) warning in
> the host dmesg. We could later improve on this with with a new (opt-in)
> exit to the host userspace.
>
> Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
> Cc: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
> Cc: Dave Martin <dave.martin@xxxxxxx>
> Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
> Cc: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> ---
> arch/arm64/kvm/handle_exit.c | 19 ++++++++++++-------
> 1 file changed, 12 insertions(+), 7 deletions(-)
>
> diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
> index 1bfe30d..fa1b18e 100644
> --- a/arch/arm64/kvm/handle_exit.c
> +++ b/arch/arm64/kvm/handle_exit.c
> @@ -135,7 +135,19 @@ static int kvm_handle_guest_debug(struct kvm_vcpu *vcpu, struct kvm_run *run)
> return ret;
> }
>
> +static int kvm_handle_unknown_ec(struct kvm_vcpu *vcpu, struct kvm_run *run)
> +{
> + u32 hsr = kvm_vcpu_get_hsr(vcpu);
> +
> + kvm_pr_unimpl("Unknown exception class: hsr: %#08x -- %s\n",
> + hsr, esr_get_class_string(hsr));
> +
> + kvm_inject_undefined(vcpu);
> + return 1;
> +}
> +
> static exit_handle_fn arm_exit_handlers[] = {
> + [0 ... ESR_ELx_EC_MAX] = kvm_handle_unknown_ec,
> [ESR_ELx_EC_WFx] = kvm_handle_wfx,
> [ESR_ELx_EC_CP15_32] = kvm_handle_cp15_32,
> [ESR_ELx_EC_CP15_64] = kvm_handle_cp15_64,
> @@ -162,13 +174,6 @@ static exit_handle_fn kvm_get_exit_handler(struct kvm_vcpu *vcpu)
> u32 hsr = kvm_vcpu_get_hsr(vcpu);
> u8 hsr_ec = ESR_ELx_EC(hsr);
>
> - if (hsr_ec >= ARRAY_SIZE(arm_exit_handlers) ||
> - !arm_exit_handlers[hsr_ec]) {
> - kvm_err("Unknown exception class: hsr: %#08x -- %s\n",
> - hsr, esr_get_class_string(hsr));
> - BUG();
> - }
> -
> return arm_exit_handlers[hsr_ec];
> }
>
> --
Reviewed-by: Christoffer Dall <cdall@xxxxxxxxxx>
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