linux-kernel - Re: [PATCH 4.19 64/89] efi: Make efi_rts_work accessible to efi page fault handler

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Date:   Thu, 19 Mar 2020 11:04:05 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Chris Wilson <chris@...is-wilson.co.uk>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Bhupesh Sharma <bhsharma@...hat.com>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Wen Yang <wenyang@...ux.alibaba.com>,
        Caspar Zhang <caspar@...ux.alibaba.com>
Subject: Re: [PATCH 4.19 64/89] efi: Make efi_rts_work accessible to efi page
 fault handler

On Thu, Mar 19, 2020 at 09:42:10AM +0000, Chris Wilson wrote:
> Quoting Greg Kroah-Hartman (2020-03-17 10:55:13)
> > From: Sai Praneeth <sai.praneeth.prakhya@...el.com>
> > 
> > commit 9dbbedaa6171247c4c7c40b83f05b200a117c2e0 upstream.
> > 
> > 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@...hat.com>
> > Suggested-by: Matt Fleming <matt@...eblueprint.co.uk>
> > Based-on-code-from: Ricardo Neri <ricardo.neri@...el.com>
> > Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>
> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> > Fixes: 3eb420e70d87 (“efi: Use a work queue to invoke EFI Runtime Services”)
> > Signed-off-by: Wen Yang <wenyang@...ux.alibaba.com>
> > Cc: Caspar Zhang <caspar@...ux.alibaba.com>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> 
> This requires the fix from
> 
> commit ef1491e791308317bb9851a0ad380c4a68b58d54
> Author: Waiman Long <longman@...hat.com>
> Date:   Wed Nov 14 09:55:40 2018 -0800
> 
>     efi: Fix debugobjects warning on 'efi_rts_work'
> 
>     The following commit:
> 
>       9dbbedaa6171 ("efi: Make efi_rts_work accessible to efi page fault handler")
> 
>     converted 'efi_rts_work' from an auto variable to a global variable.
>     However, when submitting the work, INIT_WORK_ONSTACK() was still used,
>     causing the following complaint from debugobjects:
> 
>       ODEBUG: object 00000000ed27b500 is NOT on stack 00000000c7d38760, but annotated.
> 
>     Change the macro to just INIT_WORK() to eliminate the warning.
> 
>     Signed-off-by: Waiman Long <longman@...hat.com>
>     Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
>     Acked-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>
>     Cc: Linus Torvalds <torvalds@...ux-foundation.org>
>     Cc: Peter Zijlstra <peterz@...radead.org>
>     Cc: Thomas Gleixner <tglx@...utronix.de>
>     Cc: linux-efi@...r.kernel.org
>     Fixes: 9dbbedaa6171 ("efi: Make efi_rts_work accessible to efi page fault handler")
>     Link: http://lkml.kernel.org/r/20181114175544.12860-2-ard.biesheuvel@linaro.org
>     Signed-off-by: Ingo Molnar <mingo@...nel.org>

Thanks for this, now queued up.

greg k-h
>