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Date:   Thu, 7 Feb 2019 17:38:08 +0000
From:   Hedi Berriche <hedi.berriche@hpe.com>
To:     Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Bhupesh Sharma <bhsharma@redhat.com>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>,
        linux-efi <linux-efi@vger.kernel.org>,
        the arch/x86 maintainers <x86@kernel.org>,
        Russ Anderson <rja@hpe.com>, Mike Travis <mike.travis@hpe.com>,
        Dimitri Sivanich <sivanich@hpe.com>,
        Steve Wahl <steve.wahl@hpe.com>,
        stable <stable@vger.kernel.org>
Subject: Re: [Patch v2 1/4] efi/x86: turn EFI runtime semaphore into a global
 lock
Message-ID: <20190207173808.GE6398@sarge.linuxathome.me>
Mail-Followup-To: Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Bhupesh Sharma <bhsharma@redhat.com>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>,
        linux-efi <linux-efi@vger.kernel.org>,
        the arch/x86 maintainers <x86@kernel.org>,
        Russ Anderson <rja@hpe.com>, Mike Travis <mike.travis@hpe.com>,
        Dimitri Sivanich <sivanich@hpe.com>,
        Steve Wahl <steve.wahl@hpe.com>, stable <stable@vger.kernel.org>
References: <20190207042234.25109-1-hedi.berriche@hpe.com>
 <20190207042234.25109-2-hedi.berriche@hpe.com>
 <CAKv+Gu_7yb2tf86G1f-kA3g5TVb4imQFTeL9S5qwGhJHVsmgQw@mail.gmail.com>
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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@hpe.com> 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@hpe.com>
>> Cc: Mike Travis <mike.travis@hpe.com>
>> Cc: Dimitri Sivanich <sivanich@hpe.com>
>> Cc: Steve Wahl <steve.wahl@hpe.com>
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Hedi Berriche <hedi.berriche@hpe.com>
>
>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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