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 <>
Cc: Suzuki K Poulose <>
Reviewed-by: default avatarChristoffer Dall <>
Signed-off-by: default avatarMark Rutland <>
Signed-off-by: default avatarMarc Zyngier <>
parent f050fe7a
......@@ -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));
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));
return arm_exit_handlers[hsr_ec];
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