arm64: KVM: Survive unknown traps from guests (ba4dd156) · Commits · 戴 / test

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. Cc: Dave Martin <dave.martin@arm.com> Cc: Suzuki K Poulose <suzuki.poulose@arm.com> Reviewed-by:

Christoffer Dall <christoffer.dall@linaro.org> Signed-off-by:

Mark Rutland <mark.rutland@arm.com> Signed-off-by:

Marc Zyngier <marc.zyngier@arm.com>

arch/arm64/kvm/handle_exit.c

+12 −7

Original line number	Original line	Diff line number	Diff line
	@@ -135,7 +135,19 @@ static int kvm_handle_guest_debug(struct kvm_vcpu vcpu, struct kvm_run run)
	return ret;		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[] = {		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_WFx] = kvm_handle_wfx,
	[ESR_ELx_EC_CP15_32] = kvm_handle_cp15_32,		[ESR_ELx_EC_CP15_32] = kvm_handle_cp15_32,
	[ESR_ELx_EC_CP15_64] = kvm_handle_cp15_64,		[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);		u32 hsr = kvm_vcpu_get_hsr(vcpu);
	u8 hsr_ec = ESR_ELx_EC(hsr);		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];		return arm_exit_handlers[hsr_ec];
	}		}

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