Re: [REGRESSION] Re: [patch V3 09/33] genirq/msi: Add range checking to msi_insert_desc()

["Russell King (Oracle)" <linux@armlinux.org.uk>]

On Mon, Feb 20, 2023 at 06:29:33PM +0000, Marc Zyngier wrote:
> On Mon, 20 Feb 2023 17:11:23 +0000,
> "Russell King (Oracle)" <linux@armlinux.org.uk> wrote:
> > 
> > On Fri, Nov 25, 2022 at 12:25:59AM +0100, Thomas Gleixner wrote:
> > > Per device domains provide the real domain size to the core code. This
> > > allows range checking on insertion of MSI descriptors and also paves the
> > > way for dynamic index allocations which are required e.g. for IMS. This
> > > avoids external mechanisms like bitmaps on the device side and just
> > > utilizes the core internal MSI descriptor storxe for it.
> > > 
> > > Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> > 
> > Hi Thomas,
> > 
> > This patch appears to cause a regression on Macchiatobin, delaying the
> > boot by about ten seconds due to all the warnings the kernel now
> > produces.
> > 
> > > @@ -136,11 +149,16 @@ static bool msi_desc_match(struct msi_de
> > >  
> > >  static bool msi_ctrl_valid(struct device *dev, struct msi_ctrl *ctrl)
> > >  {
> > > +	unsigned int hwsize;
> > > +
> > >  	if (WARN_ON_ONCE(ctrl->domid >= MSI_MAX_DEVICE_IRQDOMAINS ||
> > > -			 !dev->msi.data->__domains[ctrl->domid].domain ||
> > > -			 ctrl->first > ctrl->last ||
> > > -			 ctrl->first > MSI_MAX_INDEX ||
> > > -			 ctrl->last > MSI_MAX_INDEX))
> > > +			 !dev->msi.data->__domains[ctrl->domid].domain))
> > > +		return false;
> > > +
> > > +	hwsize = msi_domain_get_hwsize(dev, ctrl->domid);
> > 
> > This calls msi_get_device_domain() without taking dev->msi.data->mutex,
> > resulting in the lockdep_assert_held() firing for what seems to be every
> > MSI created by the Armada 8040 ICU driver, which suggests something isn't
> > taking the lock as you expect. Please can you take a look and propose a
> > patch to fix this regression.
> 
> Since you already worked it out, I only had to translate your words
> into the patch below, which solves it for me.

Thanks for making incorrect assumptions. I hadn't "worked it out",
I merely reported it and stated the bleeding obvious.

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