linux-kernel - Re: [RFC PATCH 12/21] vfio/pci: Skip clearing bus master on live update restored device

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Message-ID: <20251020223957.GA610352.vipinsh@google.com>
Date: Mon, 20 Oct 2025 15:39:57 -0700
From: Vipin Sharma <vipinsh@...gle.com>
To: David Matlack <dmatlack@...gle.com>
Cc: bhelgaas@...gle.com, alex.williamson@...hat.com,
	pasha.tatashin@...een.com, jgg@...pe.ca, graf@...zon.com,
	pratyush@...nel.org, gregkh@...uxfoundation.org, chrisl@...nel.org,
	rppt@...nel.org, skhawaja@...gle.com, parav@...dia.com,
	saeedm@...dia.com, kevin.tian@...el.com, jrhilke@...gle.com,
	david@...hat.com, jgowans@...zon.com, dwmw2@...radead.org,
	epetron@...zon.de, junaids@...gle.com, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, kvm@...r.kernel.org,
	linux-kselftest@...r.kernel.org
Subject: Re: [RFC PATCH 12/21] vfio/pci: Skip clearing bus master on live
 update restored device

On 2025-10-20 21:29:47, David Matlack wrote:
> On 2025-10-17 05:07 PM, Vipin Sharma wrote:
> 
> > @@ -167,6 +173,9 @@ static int vfio_pci_liveupdate_retrieve(struct liveupdate_file_handler *handler,
> >  	 */
> >  	filep->f_mapping = device->inode->i_mapping;
> >  	*file = filep;
> > +	vdev = container_of(device, struct vfio_pci_core_device, vdev);
> > +	guard(mutex)(&device->dev_set->lock);
> > +	vdev->liveupdate_restore = ser;
> 
> FYI, this causes a build failure for me:
> 
> drivers/vfio/pci/vfio_pci_liveupdate.c:381:3: error: cannot jump from this goto statement to its label
>   381 |                 goto err_get_registration;
>       |                 ^
> drivers/vfio/pci/vfio_pci_liveupdate.c:394:2: note: jump bypasses initialization of variable with __attribute__((cleanup))
>   394 |         guard(mutex)(&device->dev_set->lock);
>       |         ^
> 
> It seems you cannot jump past a guard(). Replacing the guard with
> lock/unlock fixes it, and so does putting the guard into its own inner
> statement.

I didn't get this error in my builds. I used:

  make -j$(nproc) bzImage

After your email, I tried with clang, using:

  LLVM=1 make -j$(nproc) bzImage

This one indeed fails with the error you mentioned. Thanks for catching
it. I wonder why gcc not complaining about it? May be I need to pass
some options to enable this build error on gcc.