[PATCH v6 08/18] ACPI / APEI: Move locking to the notification helper

James Morse
2018-09-21T22:18:20Z

ghes_copy_tofrom_phys() takes different locks depending on in_nmi().
This doesn't work when we have multiple NMI-like notifications, that
can interrupt each other.

Now that NOTIFY_SEA is always called as an NMI, move the lock-taking
to the notification helper. The helper will always know which lock
to take. This avoids ghes_copy_tofrom_phys() taking a guess based
on in_nmi().

This splits NOTIFY_NMI and NOTIFY_SEA to use different locks. All
the other notifications use ghes_proc(), and are called in process
or IRQ context. Move the spin_lock_irqsave() around their ghes_proc()
calls.

Signed-off-by: James Morse <james.morse@arm.com>
---
Changes since v5:
* Moved locking further out, to allow no-irq-masking in the future.

drivers/acpi/apei/ghes.c | 40 +++++++++++++++++++++++++++++-----------
1 file changed, 29 insertions(+), 11 deletions(-)

diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
index 2880547e13b8..ed8669a6c100 100644
--- a/drivers/acpi/apei/ghes.c
+++ b/drivers/acpi/apei/ghes.c
@@ -113,12 +113,13 @@ 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.
- *
- * These 2 spinlocks are used to prevent the fixmap entries from being used
- * simultaneously.
*/
-static DEFINE_RAW_SPINLOCK(ghes_ioremap_lock_nmi);
-static DEFINE_SPINLOCK(ghes_ioremap_lock_irq);
+
+/*
+ * Used by ghes_proc() to prevent non-NMI notifications from interacting.
+ * This also protects the FIX_APEI_GHES_IRQ fixmap slot.
+ */
+static DEFINE_SPINLOCK(ghes_notify_lock_irq);

static struct gen_pool *ghes_estatus_pool;
static unsigned long ghes_estatus_pool_size_request;
@@ -291,7 +292,6 @@ static void ghes_copy_tofrom_phys(void *buffer, u64 paddr, u32 len,
int from_phys)
{
void __iomem *vaddr;
- unsigned long flags = 0;
int in_nmi = in_nmi();
u64 offset;
u32 trunk;
@@ -299,10 +299,8 @@ static void ghes_copy_tofrom_phys(void *buffer, u64 paddr, u32 len,
while (len > 0) {
offset = paddr - (paddr & PAGE_MASK);
if (in_nmi) {
- raw_spin_lock(&ghes_ioremap_lock_nmi);
vaddr = ghes_ioremap_pfn_nmi(paddr >> PAGE_SHIFT);
} else {
- spin_lock_irqsave(&ghes_ioremap_lock_irq, flags);
vaddr = ghes_ioremap_pfn_irq(paddr >> PAGE_SHIFT);
}
trunk = PAGE_SIZE - offset;
@@ -316,10 +314,8 @@ static void ghes_copy_tofrom_phys(void *buffer, u64 paddr, u32 len,
buffer += trunk;
if (in_nmi) {
ghes_iounmap_nmi();
- raw_spin_unlock(&ghes_ioremap_lock_nmi);
} else {
ghes_iounmap_irq();
- spin_unlock_irqrestore(&ghes_ioremap_lock_irq, flags);
}
}
}
@@ -928,8 +924,11 @@ static void ghes_add_timer(struct ghes *ghes)
static void ghes_poll_func(struct timer_list *t)
{
struct ghes *ghes = from_timer(ghes, t, timer);
+ unsigned long flags;

+ spin_lock_irqsave(&ghes_notify_lock_irq, flags);
ghes_proc(ghes);
+ spin_unlock_irqrestore(&ghes_notify_lock_irq, flags);
if (!(ghes->flags & GHES_EXITING))
ghes_add_timer(ghes);
}
@@ -937,9 +936,12 @@ static void ghes_poll_func(struct timer_list *t)
static irqreturn_t ghes_irq_func(int irq, void *data)
{
struct ghes *ghes = data;
+ unsigned long flags;
int rc;

+ spin_lock_irqsave(&ghes_notify_lock_irq, flags);
rc = ghes_proc(ghes);
+ spin_unlock_irqrestore(&ghes_notify_lock_irq, flags);
if (rc)
return IRQ_NONE;

@@ -950,14 +952,17 @@ static int ghes_notify_hed(struct notifier_block *this, unsigned long event,
void *data)
{
struct ghes *ghes;
+ unsigned long flags;
int ret = NOTIFY_DONE;

+ spin_lock_irqsave(&ghes_notify_lock_irq, flags);
rcu_read_lock();
list_for_each_entry_rcu(ghes, &ghes_hed, list) {
if (!ghes_proc(ghes))
ret = NOTIFY_OK;
}
rcu_read_unlock();
+ spin_unlock_irqrestore(&ghes_notify_lock_irq, flags);

return ret;
}
@@ -968,6 +973,7 @@ static struct notifier_block ghes_notifier_hed = {

#ifdef CONFIG_ACPI_APEI_SEA
static LIST_HEAD(ghes_sea);
+static DEFINE_RAW_SPINLOCK(ghes_notify_lock_sea);

/*
* Return 0 only if one of the SEA error sources successfully reported an error
@@ -975,7 +981,13 @@ static LIST_HEAD(ghes_sea);
*/
int ghes_notify_sea(void)
{
- return ghes_estatus_queue_notified(&ghes_sea);
+ int rv;
+
+ raw_spin_lock(&ghes_notify_lock_sea);
+ rv = ghes_estatus_queue_notified(&ghes_sea);
+ raw_spin_unlock(&ghes_notify_lock_sea);
+
+ return rv;
}

static void ghes_sea_add(struct ghes *ghes)
@@ -1009,6 +1021,7 @@ static inline void ghes_sea_remove(struct ghes *ghes) { }
static atomic_t ghes_in_nmi = ATOMIC_INIT(0);

static LIST_HEAD(ghes_nmi);
+static DEFINE_RAW_SPINLOCK(ghes_notify_lock_nmi);

static int ghes_notify_nmi(unsigned int cmd, struct pt_regs *regs)
{
@@ -1017,8 +1030,10 @@ static int ghes_notify_nmi(unsigned int cmd, struct pt_regs *regs)
if (!atomic_add_unless(&ghes_in_nmi, 1, 1))
return ret;

+ raw_spin_lock(&ghes_notify_lock_nmi);
if (!ghes_estatus_queue_notified(&ghes_nmi))
ret = NMI_HANDLED;
+ raw_spin_unlock(&ghes_notify_lock_nmi);

atomic_dec(&ghes_in_nmi);
return ret;
@@ -1060,6 +1075,7 @@ static int ghes_probe(struct platform_device *ghes_dev)
{
struct acpi_hest_generic *generic;
struct ghes *ghes = NULL;
+ unsigned long flags;

int rc = -EINVAL;

@@ -1162,7 +1178,9 @@ static int ghes_probe(struct platform_device *ghes_dev)
ghes_edac_register(ghes, &ghes_dev->dev);

/* Handle any pending errors right away */
+ spin_lock_irqsave(&ghes_notify_lock_irq, flags);
ghes_proc(ghes);
+ spin_unlock_irqrestore(&ghes_notify_lock_irq, flags);

return 0;

--
2.19.0