Hello James,
On 3/7/2017 4:48 AM, James Morse wrote:
On 06/03/17 20:45, Tyler Baicar wrote:
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.
diff --git a/arch/arm/include/asm/kvm_arm.h b/arch/arm/include/asm/kvm_arm.h
index e22089f..a1a3dff 100644
--- a/arch/arm/include/asm/kvm_arm.h
+++ b/arch/arm/include/asm/kvm_arm.h
@@ -187,6 +187,16 @@
#define FSC_FAULT (0x04)
#define FSC_ACCESS (0x08)
#define FSC_PERM (0x0c)
+#define FSC_SEA (0x10)
+#define FSC_SEA_TTW0 (0x14)
+#define FSC_SEA_TTW1 (0x15)
+#define FSC_SEA_TTW2 (0x16)
+#define FSC_SEA_TTW3 (0x17)
+#define FSC_SECC (0x18)
+#define FSC_SECC_TTW0 (0x1c)
aarch32 doesn't have either of these 'TW0' values, it's an unused encoding.
(However ...)
+#define FSC_SECC_TTW1 (0x1d)
+#define FSC_SECC_TTW2 (0x1e)
+#define FSC_SECC_TTW3 (0x1f)
/* Hyp Prefetch Fault Address Register (HPFAR/HDFAR) */
#define HPFAR_MASK (~0xf)
#endif /* __ASM_ARM_SYSTEM_MISC_H */
diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index a5265ed..f3608c9 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -1444,8 +1463,21 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run)
/* Check the stage-2 fault is trans. fault or write fault */
fault_status = kvm_vcpu_trap_get_fault_type(vcpu);
- if (fault_status != FSC_FAULT && fault_status != FSC_PERM &&
- fault_status != FSC_ACCESS) {
+
+ /* The host kernel will handle the synchronous external abort. There
+ * is no need to pass the error into the guest.
+ */
+ if (is_abort_synchronous(fault_status)) {
+ if(handle_guest_sea((unsigned long)fault_ipa,
+ kvm_vcpu_get_hsr(vcpu))) {
... Looking further up in this function:
is_iabt = kvm_vcpu_trap_is_iabt(vcpu);
if (unlikely(!is_iabt && kvm_vcpu_dabt_isextabt(vcpu))) {
kvm_inject_vabt(vcpu);
return 1;
}
... so external data aborts will have already been 'claimed' by kvm and dealt
with, and we already have a helper for spotting external aborts. (sorry I didn't
spot it earlier).
We need to do the handle_guest_sea() before this code.
kvm_inject_vabt() makes an SError interrupt pending for the guest. This makes a
synchronous error asynchronous as the guest may have SError interrupts masked.
I guess this was the best that could be done at the time of (4055710baca8
"arm/arm64: KVM: Inject virtual abort when guest exits on external abort"), but
in the light of this firmware-first handling, I'm not sure its the right thing
to do.
Is it possible for handle_guest_sea() to return whether it actually found any
work to do? If there was none I think we should keep this kvm_inject_vabt() as
it is the existing behaviour.
Yes, I'll move the handle_guest_sea() call above this. My testing didn't
call into that if statement for some reason...it made it to the
handle_guest_sea() call successfully.
If there is no work for the GHES code to do it will return and could
still make the kvm_inject_vabt() call. It will also return and do that
same thing if the error was not fatal in GHES...would that be an issue?
+ kvm_err("Failed to handle guest SEA, FSC: EC=%#x xFSC=%#lx ESR_EL2=%#lx\n",
+ kvm_vcpu_trap_get_class(vcpu),
+ (unsigned long)kvm_vcpu_trap_get_fault(vcpu),
+ (unsigned long)kvm_vcpu_get_hsr(vcpu));
+ return -EFAULT;
+ }
+ } else if (fault_status != FSC_FAULT && fault_status != FSC_PERM &&
+ fault_status != FSC_ACCESS) {
kvm_err("Unsupported FSC: EC=%#x xFSC=%#lx ESR_EL2=%#lx\n",
kvm_vcpu_trap_get_class(vcpu),
(unsigned long)kvm_vcpu_trap_get_fault(vcpu),
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index b2d57fc..31c5171 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -602,6 +602,24 @@ 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)
+{
+ /*
+ * synchronize_rcu() will wait for nmi_exit(), so no need to
+ * rcu_read_lock().
+ */
This comment has a life of its own! Given we don't always call ghes_notify_sea()
when we interrupted un-interruptable code its not always true. I think the
rcu_read_{,un}lock() should go against the list walk (so it looks like the
examples), and ditch the comment!
:) Okay I will move the rcu calls into ghes_notify_sea() and remove the
comments.
Thanks,
Tyler
+ if(IS_ENABLED(ACPI_APEI_SEA)) {
+ rcu_read_lock();
+ ghes_notify_sea();
+ rcu_read_unlock();
+ }
+
+ return 0;
+}
+
+/*
* Dispatch a data abort to the relevant handler.
*/
asmlinkage void __exception do_mem_abort(unsigned long addr, unsigned int esr,
--
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