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In-Reply-To: <20190212172500.GB6398@sarge.linuxathome.me>
From:   Ard Biesheuvel <ard.biesheuvel@linaro.org>
Date:   Tue, 12 Feb 2019 18:26:06 +0100
Message-ID: <CAKv+Gu8yHDc+yDkSoOP6Un6bYvoMoyc-7PBXkAoiEZbTL4Vk1Q@mail.gmail.com>
Subject: Re: [Patch v2 1/4] efi/x86: turn EFI runtime semaphore into a global lock
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>
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Sender: linux-kernel-owner@vger.kernel.org
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On Tue, 12 Feb 2019 at 18:25, Hedi Berriche <hedi.berriche@hpe.com> 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@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.
>
> 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?
>

Hello Hedi,

No it doesn't. I responded 5 days ago with a suggestion on how to
address this instead.

> 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