BACKPORT: ACPI / APEI: Use separate fixmap pages for arm64 NMI-like n…

…otifications

Now that ghes notification helpers provide the fixmap slots and
take the lock themselves, multiple NMI-like notifications can
be used on arm64.

These should be named after their notification method as they can't
all be called 'NMI'. x86's NOTIFY_NMI already is, change the SEA
fixmap entry to be called FIX_APEI_GHES_SEA.

Future patches can add support for FIX_APEI_GHES_SEI and
FIX_APEI_GHES_SDEI_{NORMAL,CRITICAL}.

Because all of ghes.c builds on both architectures, provide a
constant for each fixmap entry that the architecture will never
use.

This patch is needed because Quicksilver firmware-first error handling
uses the SDEI notification type for communication between trusted
firmware and the OS. This adds needed NMI and SDEI functionality so
that the SDEI path in the kernel through APEI acts as an NMI and is
properly wired up to the APEI interfaces.

Backported from: torvalds/linux@b972d2e

Signed-off-by: James Morse <[email protected]>
Signed-off-by: Tyler Baicar <[email protected]>

arch/arm64/include/asm/fixmap.h

@@ -55,7 +55,7 @@ enum fixed_addresses {
 #ifdef CONFIG_ACPI_APEI_GHES
 	/* Used for GHES mapping from assorted contexts */
 	FIX_APEI_GHES_IRQ,
-	FIX_APEI_GHES_NMI,
+	FIX_APEI_GHES_SEA,
 #endif /* CONFIG_ACPI_APEI_GHES */
 
 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0

drivers/acpi/apei/ghes.c

@@ -958,7 +958,7 @@ int ghes_notify_sea(void)
 	int rv;
 
 	raw_spin_lock(&ghes_notify_lock_sea);
-	rv = ghes_in_nmi_spool_from_list(&ghes_sea, FIX_APEI_GHES_NMI);
+	rv = ghes_in_nmi_spool_from_list(&ghes_sea, FIX_APEI_GHES_SEA);
 	raw_spin_unlock(&ghes_notify_lock_sea);
 
 	return rv;