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Commit ba4dd156 authored by Mark Rutland's avatar Mark Rutland Committed by Marc Zyngier
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arm64: KVM: Survive unknown traps from guests 



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: default avatarChristoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
parent f050fe7a

arch/arm64/kvm/handle_exit.c

+12 −7
Original line number 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;

}



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];

}