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    Subject[PATCH V6 1/2] efi: Make efi_rts_work accessible to efi page fault handler
    Date
    From: Sai Praneeth <sai.praneeth.prakhya@intel.com>

    After the kernel has booted, if any accesses by firmware causes a page
    fault, the efi page fault handler would freeze efi_rts_wq and schedules
    a new process. To do this, the efi page fault handler needs
    efi_rts_work. Hence, make it accessible.

    There will be no race conditions in accessing this structure, because,
    all the calls to efi runtime services are already serialized.

    Tested-by: Bhupesh Sharma <bhsharma@redhat.com>
    Suggested-by: Matt Fleming <matt@codeblueprint.co.uk>
    Based-on-code-from: Ricardo Neri <ricardo.neri@intel.com>
    Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
    Cc: Al Stone <astone@redhat.com>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Ingo Molnar <mingo@kernel.org>
    Cc: Andy Lutomirski <luto@kernel.org>
    Cc: Bhupesh Sharma <bhsharma@redhat.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
    ---
    drivers/firmware/efi/runtime-wrappers.c | 53 ++++++---------------------------
    include/linux/efi.h | 36 ++++++++++++++++++++++
    2 files changed, 45 insertions(+), 44 deletions(-)

    diff --git a/drivers/firmware/efi/runtime-wrappers.c b/drivers/firmware/efi/runtime-wrappers.c
    index aa66cbf23512..b18b2d864c2c 100644
    --- a/drivers/firmware/efi/runtime-wrappers.c
    +++ b/drivers/firmware/efi/runtime-wrappers.c
    @@ -45,39 +45,7 @@
    #define __efi_call_virt(f, args...) \
    __efi_call_virt_pointer(efi.systab->runtime, f, args)

    -/* efi_runtime_service() function identifiers */
    -enum efi_rts_ids {
    - GET_TIME,
    - SET_TIME,
    - GET_WAKEUP_TIME,
    - SET_WAKEUP_TIME,
    - GET_VARIABLE,
    - GET_NEXT_VARIABLE,
    - SET_VARIABLE,
    - QUERY_VARIABLE_INFO,
    - GET_NEXT_HIGH_MONO_COUNT,
    - UPDATE_CAPSULE,
    - QUERY_CAPSULE_CAPS,
    -};
    -
    -/*
    - * efi_runtime_work: Details of EFI Runtime Service work
    - * @arg<1-5>: EFI Runtime Service function arguments
    - * @status: Status of executing EFI Runtime Service
    - * @efi_rts_id: EFI Runtime Service function identifier
    - * @efi_rts_comp: Struct used for handling completions
    - */
    -struct efi_runtime_work {
    - void *arg1;
    - void *arg2;
    - void *arg3;
    - void *arg4;
    - void *arg5;
    - efi_status_t status;
    - struct work_struct work;
    - enum efi_rts_ids efi_rts_id;
    - struct completion efi_rts_comp;
    -};
    +struct efi_runtime_work efi_rts_work;

    /*
    * efi_queue_work: Queue efi_runtime_service() and wait until it's done
    @@ -91,7 +59,6 @@ struct efi_runtime_work {
    */
    #define efi_queue_work(_rts, _arg1, _arg2, _arg3, _arg4, _arg5) \
    ({ \
    - struct efi_runtime_work efi_rts_work; \
    efi_rts_work.status = EFI_ABORTED; \
    \
    init_completion(&efi_rts_work.efi_rts_comp); \
    @@ -184,18 +151,16 @@ static DEFINE_SEMAPHORE(efi_runtime_lock);
    */
    static void efi_call_rts(struct work_struct *work)
    {
    - struct efi_runtime_work *efi_rts_work;
    void *arg1, *arg2, *arg3, *arg4, *arg5;
    efi_status_t status = EFI_NOT_FOUND;

    - efi_rts_work = container_of(work, struct efi_runtime_work, work);
    - arg1 = efi_rts_work->arg1;
    - arg2 = efi_rts_work->arg2;
    - arg3 = efi_rts_work->arg3;
    - arg4 = efi_rts_work->arg4;
    - arg5 = efi_rts_work->arg5;
    + arg1 = efi_rts_work.arg1;
    + arg2 = efi_rts_work.arg2;
    + arg3 = efi_rts_work.arg3;
    + arg4 = efi_rts_work.arg4;
    + arg5 = efi_rts_work.arg5;

    - switch (efi_rts_work->efi_rts_id) {
    + switch (efi_rts_work.efi_rts_id) {
    case GET_TIME:
    status = efi_call_virt(get_time, (efi_time_t *)arg1,
    (efi_time_cap_t *)arg2);
    @@ -253,8 +218,8 @@ static void efi_call_rts(struct work_struct *work)
    */
    pr_err("Requested executing invalid EFI Runtime Service.\n");
    }
    - efi_rts_work->status = status;
    - complete(&efi_rts_work->efi_rts_comp);
    + efi_rts_work.status = status;
    + complete(&efi_rts_work.efi_rts_comp);
    }

    static efi_status_t virt_efi_get_time(efi_time_t *tm, efi_time_cap_t *tc)
    diff --git a/include/linux/efi.h b/include/linux/efi.h
    index 401e4b254e30..855992b15269 100644
    --- a/include/linux/efi.h
    +++ b/include/linux/efi.h
    @@ -1659,7 +1659,43 @@ struct linux_efi_tpm_eventlog {

    extern int efi_tpm_eventlog_init(void);

    +/* efi_runtime_service() function identifiers */
    +enum efi_rts_ids {
    + GET_TIME,
    + SET_TIME,
    + GET_WAKEUP_TIME,
    + SET_WAKEUP_TIME,
    + GET_VARIABLE,
    + GET_NEXT_VARIABLE,
    + SET_VARIABLE,
    + QUERY_VARIABLE_INFO,
    + GET_NEXT_HIGH_MONO_COUNT,
    + UPDATE_CAPSULE,
    + QUERY_CAPSULE_CAPS,
    +};
    +
    +/*
    + * efi_runtime_work: Details of EFI Runtime Service work
    + * @arg<1-5>: EFI Runtime Service function arguments
    + * @status: Status of executing EFI Runtime Service
    + * @efi_rts_id: EFI Runtime Service function identifier
    + * @efi_rts_comp: Struct used for handling completions
    + */
    +struct efi_runtime_work {
    + void *arg1;
    + void *arg2;
    + void *arg3;
    + void *arg4;
    + void *arg5;
    + efi_status_t status;
    + struct work_struct work;
    + enum efi_rts_ids efi_rts_id;
    + struct completion efi_rts_comp;
    +};
    +
    /* Workqueue to queue EFI Runtime Services */
    extern struct workqueue_struct *efi_rts_wq;

    +extern struct efi_runtime_work efi_rts_work;
    +
    #endif /* _LINUX_EFI_H */
    --
    2.7.4
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