[PATCH v4 08/12] ACPI / APEI: Split fixmap pages for arm64 NMI-like notifications

[James Morse]

Now that ghes uses the fixmap addresses and locks via some indirection
we can support multiple NMI-like notifications on arm64.

These should be named after their notification method. x86's
NOTIFY_NMI already is, move it to live with the ghes_nmi list.
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}.

Signed-off-by: James Morse <james.morse at arm.com>
Reviewed-by: Punit Agrawal <punit.agrawal at arm.com>
Tested-by: Tyler Baicar <tbaicar at codeaurora.org>
---
Changes since v3:
 * idx/lock are now in a separate struct.
 * Add to the comment above ghes_fixmap_lock_irq so that it makes more
   sense in isolation.

 arch/arm64/include/asm/fixmap.h |  4 +++-
 drivers/acpi/apei/ghes.c        | 12 ++++++++----
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/include/asm/fixmap.h b/arch/arm64/include/asm/fixmap.h
index ec1e6d6fa14c..c3974517c2cb 100644
--- a/arch/arm64/include/asm/fixmap.h
+++ b/arch/arm64/include/asm/fixmap.h
@@ -55,7 +55,9 @@ enum fixed_addresses {
 #ifdef CONFIG_ACPI_APEI_GHES
 	/* Used for GHES mapping from assorted contexts */
 	FIX_APEI_GHES_IRQ,
-	FIX_APEI_GHES_NMI,
+#ifdef CONFIG_ACPI_APEI_SEA
+	FIX_APEI_GHES_SEA,
+#endif
 #endif /* CONFIG_ACPI_APEI_GHES */
 
 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0
diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
index 13bb3bb94fbd..014966bdd0a7 100644
--- a/drivers/acpi/apei/ghes.c
+++ b/drivers/acpi/apei/ghes.c
@@ -117,8 +117,10 @@ static DEFINE_MUTEX(ghes_list_mutex);
  * from BIOS to Linux can be determined only in NMI, IRQ or timer
  * handler, but general ioremap can not be used in atomic context, so
  * the fixmap is used instead.
+ * This lock protects access to the FIX_APEI_GHES_IRQ entry.
+ * NMI-like notifications use DEFINE_GHES_NMI_FIXMAP() to pair a fixmap
+ * entry and a lock.
  */
-static DEFINE_GHES_NMI_FIXMAP(nmi_fixmap, FIX_APEI_GHES_NMI);
 static DEFINE_SPINLOCK(ghes_fixmap_lock_irq);
 
 static struct gen_pool *ghes_estatus_pool;
@@ -948,6 +950,7 @@ static struct notifier_block ghes_notifier_hed = {
 
 #ifdef CONFIG_ACPI_APEI_SEA
 static LIST_HEAD(ghes_sea);
+static DEFINE_GHES_NMI_FIXMAP(sea_fixmap, FIX_APEI_GHES_SEA);
 
 /*
  * Return 0 only if one of the SEA error sources successfully reported an error
@@ -960,7 +963,7 @@ int ghes_notify_sea(void)
 
 static void ghes_sea_add(struct ghes *ghes)
 {
-	ghes->nmi_fixmap = &nmi_fixmap;
+	ghes->nmi_fixmap = &sea_fixmap;
 	ghes_estatus_queue_grow_pool(ghes);
 
 	mutex_lock(&ghes_list_mutex);
@@ -984,12 +987,13 @@ static inline void ghes_sea_remove(struct ghes *ghes) { }
 
 #ifdef CONFIG_HAVE_ACPI_APEI_NMI
 /*
- * NMI may be triggered on any CPU, so ghes_in_nmi is used for
- * having only one concurrent reader.
+ * NOTIFY_NMI may be triggered on any CPU, so ghes_in_nmi is
+ * used for having only one concurrent reader.
  */
 static atomic_t ghes_in_nmi = ATOMIC_INIT(0);
 
 static LIST_HEAD(ghes_nmi);
+static DEFINE_GHES_NMI_FIXMAP(nmi_fixmap, FIX_APEI_GHES_NMI);
 
 static int ghes_notify_nmi(unsigned int cmd, struct pt_regs *regs)
 {
-- 
2.16.2