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Date:   Tue, 12 Feb 2019 23:46:00 +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: <20190212234600.GL6398@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>
 <20190207173808.GE6398@sarge.linuxathome.me>
 <20190212172500.GB6398@sarge.linuxathome.me>
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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@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?

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