This is a note to let you know that I've just added the patch titled
arm: 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;a=summary
The filename of the patch is:
arm-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@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Tue Dec 12 13:26:17 CET 2017
From: Mark Rutland <mark.rutland@xxxxxxx>
Date: Mon, 20 Feb 2017 12:30:11 +0000
Subject: arm: KVM: Survive unknown traps from guests
From: Mark Rutland <mark.rutland@xxxxxxx>
[ Upstream commit f050fe7a9164945dd1c28be05bf00e8cfb082ccf ]
Currently we BUG() if we see a HSR.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 0406C.c, all currently
unallocated HSR EC encodings are reserved, and per ARM DDI
0487A.k_iss10775, page G6-4395, 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@xxxxxxx>
Cc: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
Reviewed-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm/include/asm/kvm_arm.h | 1 +
arch/arm/kvm/handle_exit.c | 19 ++++++++++++-------
2 files changed, 13 insertions(+), 7 deletions(-)
--- a/arch/arm/include/asm/kvm_arm.h
+++ b/arch/arm/include/asm/kvm_arm.h
@@ -208,6 +208,7 @@
#define HSR_EC_IABT_HYP (0x21)
#define HSR_EC_DABT (0x24)
#define HSR_EC_DABT_HYP (0x25)
+#define HSR_EC_MAX (0x3f)
#define HSR_WFI_IS_WFE (_AC(1, UL) << 0)
--- a/arch/arm/kvm/handle_exit.c
+++ b/arch/arm/kvm/handle_exit.c
@@ -79,7 +79,19 @@ static int kvm_handle_wfx(struct kvm_vcp
return 1;
}
+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\n",
+ hsr);
+
+ kvm_inject_undefined(vcpu);
+ return 1;
+}
+
static exit_handle_fn arm_exit_handlers[] = {
+ [0 ... HSR_EC_MAX] = kvm_handle_unknown_ec,
[HSR_EC_WFI] = kvm_handle_wfx,
[HSR_EC_CP15_32] = kvm_handle_cp15_32,
[HSR_EC_CP15_64] = kvm_handle_cp15_64,
@@ -98,13 +110,6 @@ static exit_handle_fn kvm_get_exit_handl
{
u8 hsr_ec = kvm_vcpu_trap_get_class(vcpu);
- if (hsr_ec >= ARRAY_SIZE(arm_exit_handlers) ||
- !arm_exit_handlers[hsr_ec]) {
- kvm_err("Unknown exception class: hsr: %#08x\n",
- (unsigned int)kvm_vcpu_get_hsr(vcpu));
- BUG();
- }
-
return arm_exit_handlers[hsr_ec];
}
Patches currently in stable-queue which might be from mark.rutland@xxxxxxx 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