Re: [PATCH V3 10/10] arm64: KVM: add guest SEA support

From: Baicar, Tyler
Date: Fri Oct 14 2016 - 17:59:10 EST

On 10/14/2016 2:38 AM, Punit Agrawal wrote:
"Baicar, Tyler" <tbaicar@xxxxxxxxxxxxxx> writes:

Hello Punit,

On 10/13/2016 7:14 AM, Punit Agrawal wrote:
Hi Tyler,

I know I've had my last comment already ;), but I thought I'd rather
raise the question than stay confused...

Tyler Baicar <tbaicar@xxxxxxxxxxxxxx> writes:

Currently external aborts are unsupported by the guest abort
handling. Add handling for SEAs so that the host kernel reports
SEAs which occur in the guest kernel.

Signed-off-by: Tyler Baicar <tbaicar@xxxxxxxxxxxxxx>
arch/arm/include/asm/kvm_arm.h | 1 +
arch/arm/include/asm/system_misc.h | 5 +++++
arch/arm/kvm/mmu.c | 15 +++++++++++++--
arch/arm64/include/asm/kvm_arm.h | 1 +
arch/arm64/include/asm/system_misc.h | 2 ++
arch/arm64/mm/fault.c | 13 +++++++++++++
6 files changed, 35 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 81cb7ad..d714432 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -597,6 +597,19 @@ static const char *fault_name(unsigned int esr)
+ * Handle Synchronous External Aborts that occur in a guest kernel.
+ */
+int handle_guest_sea(unsigned long addr, unsigned int esr)
+ atomic_notifier_call_chain(&sea_handler_chain, 0, NULL);
+ pr_err("Synchronous External Abort: %s (0x%08x) at 0x%016lx\n",
+ fault_name(esr), esr, addr);
+ return 0;
Don't we need to pass the abort to the guest?
This requires some infrastructure to implement virtual "ACPI platform
error interface" to expose the details of the abort to the guest. This
patchset does not cover that and focuses on feature parity with other
architectures that support APEI. There are discussions among Linaro
partners about how this can be achieved in the long term, but that
work is outside the scope of this patchset. This patch will ensure
that if a guest encounters one of these errors then it will be
reported before getting killed. Before this patch we would just get an
unsupported FSC print out and then the guest would be killed.

I think we might be talking about different things though.

I am referring to the injection of the synchronous external abort into
the guest - similar to what's been done for prefetch abort in the

Maybe there is no benefit in passing the abort to the guest. In that
case, can you please add a comment where you handle external abort
(FSC_EXTABT) in kvm_guest_handle_abort.
Yes, I will add a comment there in the next version.


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