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

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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.


---
 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



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