Re: [Patch v2 1/4] efi/x86: turn EFI runtime semaphore into a global lock

Hedi Berriche <hedi.berriche@xxxxxxx> · Tue, 12 Feb 2019 23:46:00 +0000

On Tue, Feb 12, 2019 at 17:25 Hedi Berriche wrote:
On Thu, Feb 07, 2019 at 17:38 Hedi Berriche wrote:
On Thu, Feb 07, 2019 at 16:05 Ard Biesheuvel wrote:
On Thu, 7 Feb 2019 at 05:23, Hedi Berriche <hedi.berriche@xxxxxxx> wrote:

Make efi_runtime_lock semaphore global so that it can be used by EFI
runtime callers that may be defined outside efi/runtime-wrappers.c.

Also now that efi_runtime_lock semaphore is no longer static, rename it
to efi_runtime_sem so it doesn't clash with the efi_runtime_lock spinlock
defined in arch/x86/platform/efi/efi_64.c when CONFIG_EFI_MIXED is
enabled.

The immediate motivation of this change is to serialise UV platform BIOS
calls using the efi_runtime_sem semaphore.

No functional changes.

Cc: Russ Anderson <rja@xxxxxxx>
Cc: Mike Travis <mike.travis@xxxxxxx>
Cc: Dimitri Sivanich <sivanich@xxxxxxx>
Cc: Steve Wahl <steve.wahl@xxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Hedi Berriche <hedi.berriche@xxxxxxx>

Hello Hedi,

Hi Ard,

Same feedback as on v1: please don't rename the lock.

With the efi_runtime_lock semaphore being no longer static, not renaming it
will cause a compile failure as it will clash with the declaration of the
efi_runtime_lock *spinlock* in arch/x86/platform/efi/efi_64.c in the
CONFIG_EFI_MIXED case.

Ard,

Any comments on whether resolving the conflict between

	{efi_runtime_lock, drivers/firmware/efi/runtime-wrappers.c}

and
	{efi_runtime_lock, arch/x86/platform/efi/efi_64.c}

provides the required justification for renaming the efi_runtime_lock semaphore?

Ard,

Apologies for sending this email which must have come across as absurd given
the *second* email you sent on 2019-02-07 19:38:42.

The trouble is that I *never* received that email (nor the one you sent today
2019-02-12 17:26:06 as reply to this one) because for some reason my email
address was dropped from the distribution list.

It's only about 30 minutes ago that a colleague brought it up to my attention
and forwarded both emails:

	Thu,  7 Feb 2019 20:38:42 +0100
	Tue, 12 Feb 2019 18:26:06 +0100

No idea how my email address got dropped but I wanted to make sure to explain
the seemingly absurd email I sent today as well as the lack of comment on your
earlier email.

Cheers,
Hedi.
---
drivers/firmware/efi/runtime-wrappers.c | 60 ++++++++++++-------------
include/linux/efi.h                     |  3 ++
2 files changed, 33 insertions(+), 30 deletions(-)

diff --git a/drivers/firmware/efi/runtime-wrappers.c b/drivers/firmware/efi/runtime-wrappers.c
index 8903b9ccfc2b..ec60d6227925 100644
--- a/drivers/firmware/efi/runtime-wrappers.c
+++ b/drivers/firmware/efi/runtime-wrappers.c
@@ -53,7 +53,7 @@ struct efi_runtime_work efi_rts_work;
* @rts_arg<1-5>:      efi_runtime_service() function arguments
*
* Accesses to efi_runtime_services() are serialized by a binary
- * semaphore (efi_runtime_lock) and caller waits until the work is
+ * semaphore (efi_runtime_sem) and caller waits until the work is
* finished, hence _only_ one work is queued at a time and the caller
* thread waits for completion.
*/
@@ -144,7 +144,7 @@ void efi_call_virt_check_flags(unsigned long flags, const char *call)
* none of the remaining functions are actually ever called at runtime.
* So let's just use a single lock to serialize all Runtime Services calls.
*/
-static DEFINE_SEMAPHORE(efi_runtime_lock);
+DEFINE_SEMAPHORE(efi_runtime_sem);

/*
* Calls the appropriate efi_runtime_service() with the appropriate
@@ -233,10 +233,10 @@ static efi_status_t virt_efi_get_time(efi_time_t *tm, efi_time_cap_t *tc)
{
      efi_status_t status;

-       if (down_interruptible(&efi_runtime_lock))
+       if (down_interruptible(&efi_runtime_sem))
              return EFI_ABORTED;
      status = efi_queue_work(GET_TIME, tm, tc, NULL, NULL, NULL);
-       up(&efi_runtime_lock);
+       up(&efi_runtime_sem);
      return status;
}

@@ -244,10 +244,10 @@ static efi_status_t virt_efi_set_time(efi_time_t *tm)
{
      efi_status_t status;

-       if (down_interruptible(&efi_runtime_lock))
+       if (down_interruptible(&efi_runtime_sem))
              return EFI_ABORTED;
      status = efi_queue_work(SET_TIME, tm, NULL, NULL, NULL, NULL);
-       up(&efi_runtime_lock);
+       up(&efi_runtime_sem);
      return status;
}

@@ -257,11 +257,11 @@ static efi_status_t virt_efi_get_wakeup_time(efi_bool_t *enabled,
{
      efi_status_t status;

-       if (down_interruptible(&efi_runtime_lock))
+       if (down_interruptible(&efi_runtime_sem))
              return EFI_ABORTED;
      status = efi_queue_work(GET_WAKEUP_TIME, enabled, pending, tm, NULL,
                              NULL);
-       up(&efi_runtime_lock);
+       up(&efi_runtime_sem);
      return status;
}

@@ -269,11 +269,11 @@ static efi_status_t virt_efi_set_wakeup_time(efi_bool_t enabled, efi_time_t *tm)
{
      efi_status_t status;

-       if (down_interruptible(&efi_runtime_lock))
+       if (down_interruptible(&efi_runtime_sem))
              return EFI_ABORTED;
      status = efi_queue_work(SET_WAKEUP_TIME, &enabled, tm, NULL, NULL,
                              NULL);
-       up(&efi_runtime_lock);
+       up(&efi_runtime_sem);
      return status;
}

@@ -285,11 +285,11 @@ static efi_status_t virt_efi_get_variable(efi_char16_t *name,
{
      efi_status_t status;

-       if (down_interruptible(&efi_runtime_lock))
+       if (down_interruptible(&efi_runtime_sem))
              return EFI_ABORTED;
      status = efi_queue_work(GET_VARIABLE, name, vendor, attr, data_size,
                              data);
-       up(&efi_runtime_lock);
+       up(&efi_runtime_sem);
      return status;
}

@@ -299,11 +299,11 @@ static efi_status_t virt_efi_get_next_variable(unsigned long *name_size,
{
      efi_status_t status;

-       if (down_interruptible(&efi_runtime_lock))
+       if (down_interruptible(&efi_runtime_sem))
              return EFI_ABORTED;
      status = efi_queue_work(GET_NEXT_VARIABLE, name_size, name, vendor,
                              NULL, NULL);
-       up(&efi_runtime_lock);
+       up(&efi_runtime_sem);
      return status;
}

@@ -315,11 +315,11 @@ static efi_status_t virt_efi_set_variable(efi_char16_t *name,
{
      efi_status_t status;

-       if (down_interruptible(&efi_runtime_lock))
+       if (down_interruptible(&efi_runtime_sem))
              return EFI_ABORTED;
      status = efi_queue_work(SET_VARIABLE, name, vendor, &attr, &data_size,
                              data);
-       up(&efi_runtime_lock);
+       up(&efi_runtime_sem);
      return status;
}

@@ -330,12 +330,12 @@ virt_efi_set_variable_nonblocking(efi_char16_t *name, efi_guid_t *vendor,
{
      efi_status_t status;

-       if (down_trylock(&efi_runtime_lock))
+       if (down_trylock(&efi_runtime_sem))
              return EFI_NOT_READY;

      status = efi_call_virt(set_variable, name, vendor, attr, data_size,
                             data);
-       up(&efi_runtime_lock);
+       up(&efi_runtime_sem);
      return status;
}

@@ -350,11 +350,11 @@ static efi_status_t virt_efi_query_variable_info(u32 attr,
      if (efi.runtime_version < EFI_2_00_SYSTEM_TABLE_REVISION)
              return EFI_UNSUPPORTED;

-       if (down_interruptible(&efi_runtime_lock))
+       if (down_interruptible(&efi_runtime_sem))
              return EFI_ABORTED;
      status = efi_queue_work(QUERY_VARIABLE_INFO, &attr, storage_space,
                              remaining_space, max_variable_size, NULL);
-       up(&efi_runtime_lock);
+       up(&efi_runtime_sem);
      return status;
}

@@ -369,12 +369,12 @@ virt_efi_query_variable_info_nonblocking(u32 attr,
      if (efi.runtime_version < EFI_2_00_SYSTEM_TABLE_REVISION)
              return EFI_UNSUPPORTED;

-       if (down_trylock(&efi_runtime_lock))
+       if (down_trylock(&efi_runtime_sem))
              return EFI_NOT_READY;

      status = efi_call_virt(query_variable_info, attr, storage_space,
                             remaining_space, max_variable_size);
-       up(&efi_runtime_lock);
+       up(&efi_runtime_sem);
      return status;
}

@@ -382,11 +382,11 @@ static efi_status_t virt_efi_get_next_high_mono_count(u32 *count)
{
      efi_status_t status;

-       if (down_interruptible(&efi_runtime_lock))
+       if (down_interruptible(&efi_runtime_sem))
              return EFI_ABORTED;
      status = efi_queue_work(GET_NEXT_HIGH_MONO_COUNT, count, NULL, NULL,
                              NULL, NULL);
-       up(&efi_runtime_lock);
+       up(&efi_runtime_sem);
      return status;
}

@@ -395,14 +395,14 @@ static void virt_efi_reset_system(int reset_type,
                                unsigned long data_size,
                                efi_char16_t *data)
{
-       if (down_interruptible(&efi_runtime_lock)) {
+       if (down_interruptible(&efi_runtime_sem)) {
              pr_warn("failed to invoke the reset_system() runtime service:\n"
                      "could not get exclusive access to the firmware\n");
              return;
      }
      efi_rts_work.efi_rts_id = RESET_SYSTEM;
      __efi_call_virt(reset_system, reset_type, status, data_size, data);
-       up(&efi_runtime_lock);
+       up(&efi_runtime_sem);
}

static efi_status_t virt_efi_update_capsule(efi_capsule_header_t **capsules,
@@ -414,11 +414,11 @@ static efi_status_t virt_efi_update_capsule(efi_capsule_header_t **capsules,
      if (efi.runtime_version < EFI_2_00_SYSTEM_TABLE_REVISION)
              return EFI_UNSUPPORTED;

-       if (down_interruptible(&efi_runtime_lock))
+       if (down_interruptible(&efi_runtime_sem))
              return EFI_ABORTED;
      status = efi_queue_work(UPDATE_CAPSULE, capsules, &count, &sg_list,
                              NULL, NULL);
-       up(&efi_runtime_lock);
+       up(&efi_runtime_sem);
      return status;
}

@@ -432,11 +432,11 @@ static efi_status_t virt_efi_query_capsule_caps(efi_capsule_header_t **capsules,
      if (efi.runtime_version < EFI_2_00_SYSTEM_TABLE_REVISION)
              return EFI_UNSUPPORTED;

-       if (down_interruptible(&efi_runtime_lock))
+       if (down_interruptible(&efi_runtime_sem))
              return EFI_ABORTED;
      status = efi_queue_work(QUERY_CAPSULE_CAPS, capsules, &count,
                              max_size, reset_type, NULL);
-       up(&efi_runtime_lock);
+       up(&efi_runtime_sem);
      return status;
}

diff --git a/include/linux/efi.h b/include/linux/efi.h
index 45ff763fba76..930cd20842b8 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1745,6 +1745,9 @@ extern struct efi_runtime_work efi_rts_work;
/* Workqueue to queue EFI Runtime Services */
extern struct workqueue_struct *efi_rts_wq;

+/* EFI runtime semaphore */
+extern struct semaphore efi_runtime_sem;
+
struct linux_efi_memreserve {
      int             size;                   // allocated size of the array
      atomic_t        count;                  // number of entries used
--
2.20.1


--
Be careful of reading health books, you might die of a misprint.
	-- Mark Twain

--
Be careful of reading health books, you might die of a misprint.
	-- Mark Twain

--
Be careful of reading health books, you might die of a misprint.
	-- Mark Twain






