This is a note to let you know that I've just added the patch titled
arm64: KVM: Survive unknown traps from guests
to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: arm64-kvm-survive-unknown-traps-from-guests.patch and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From foo@baz Tue Dec 12 13:26:17 CET 2017
From: Mark Rutland mark.rutland@arm.com Date: Mon, 20 Feb 2017 12:30:12 +0000 Subject: arm64: KVM: Survive unknown traps from guests
From: Mark Rutland mark.rutland@arm.com
[ Upstream commit ba4dd156eabdca93501d92a980ba27fa5f4bbd27 ]
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 Signed-off-by: Sasha Levin alexander.levin@verizon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm64/kvm/handle_exit.c | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-)
--- a/arch/arm64/kvm/handle_exit.c +++ b/arch/arm64/kvm/handle_exit.c @@ -125,7 +125,19 @@ static int kvm_handle_guest_debug(struct 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, @@ -151,13 +163,6 @@ static exit_handle_fn kvm_get_exit_handl 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]; }
Patches currently in stable-queue which might be from mark.rutland@arm.com are
queue-4.9/arm-8657-1-uaccess-consistently-check-object-sizes.patch queue-4.9/arm-kvm-survive-unknown-traps-from-guests.patch queue-4.9/sparc64-mm-set-fields-in-deferred-pages.patch queue-4.9/bus-arm-cci-fix-use-of-smp_processor_id-in-preemptible-context.patch queue-4.9/arm64-kvm-survive-unknown-traps-from-guests.patch queue-4.9/bus-arm-ccn-fix-use-of-smp_processor_id-in-preemptible-context.patch