Hi Marc,

On 26/03/18 18:49, Marc Zyngier wrote:

On 22/03/18 18:14, James Morse wrote:

quoted

To ensure APEI always takes the same locks when processing a notification
we need the nmi-like callers to always call APEI in_nmi(). Add a helper
to do the work and claim the notification.

When KVM or the arch code takes an exception that might be a RAS
notification, it asks the APEI firmware-first code whether it wants
to claim the exception. We can then go on to see if (a future)
kernel-first mechanism wants to claim the notification, before
falling through to the existing default behaviour.

The NOTIFY_SEA code was merged before we had multiple, possibly
interacting, NMI-like notifications and the need to consider kernel
first in the future. Make the 'claiming' behaviour explicit.

As we're restructuring the APEI code to allow multiple NMI-like
notifications, any notification that might interrupt interrupts-masked
code must always be wrapped in nmi_enter()/nmi_exit(). This allows APEI
to use in_nmi() to choose between the raw/regular spinlock routines.

We mask SError over this window to prevent an asynchronous RAS error
arriving and tripping 'nmi_enter()'s BUG_ON(in_nmi()).

quoted

diff --git a/arch/arm64/include/asm/kvm_ras.h b/arch/arm64/include/asm/kvm_ras.h
index 5f72b07b7912..9d52bc333110 100644
--- a/arch/arm64/include/asm/kvm_ras.h
+++ b/arch/arm64/include/asm/kvm_ras.h

@@ -4,8 +4,26 @@
 #ifndef __ARM64_KVM_RAS_H__
 #define __ARM64_KVM_RAS_H__
 
+#include <linux/acpi.h>
+#include <linux/errno.h>
 #include <linux/types.h>
 
-int kvm_handle_guest_sea(phys_addr_t addr, unsigned int esr);
+#include <asm/acpi.h>
+
+/*
+ * Was this synchronous external abort a RAS notification?
+ * Returns '0' for errors handled by some RAS subsystem, or -ENOENT.
+ *
+ * Call with irqs unmaksed.

Self-Nit: unmasked.

quoted

+ */
+static inline int kvm_handle_guest_sea(phys_addr_t addr, unsigned int esr)
+{
+	int ret = -ENOENT;
+
+	if (IS_ENABLED(CONFIG_ACPI_APEI_SEA))
+		ret = apei_claim_sea(NULL);

Nit: it is a bit odd to see this "IS_ENABLED(CONFIG_ACPI_APEI_SEA)"
check both in this function and in the only other function this calls
(apei_claim_sea). Could this somehow be improved by having a dummy
apei_claim_sea if CONFIG_ACPI_APEI doesn't exist?

Good point. Your suggestion also avoids more #ifdefs in the C file, which is
what I was trying to avoid.

quoted

+
+	return ret;
+}
 
 #endif /* __ARM64_KVM_RAS_H__ */

Otherwise:

Acked-by: Marc Zyngier <redacted>

Thanks!


James