Re: [Intel-gfx] [PATCH v3 3/3] x86/quirks: Fix stolen detection with integrated + discrete GPU

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Mon, Jan 10, 2022 at 11:32:11AM -0600, Bjorn Helgaas wrote:
> On Mon, Jan 10, 2022 at 12:11:36PM -0500, Rodrigo Vivi wrote:
> > On Fri, Jan 07, 2022 at 08:57:32PM -0600, Bjorn Helgaas wrote:
> > > On Fri, Jan 07, 2022 at 01:05:16PM -0800, Lucas De Marchi wrote:
> > > > early_pci_scan_bus() does a depth-first traversal, possibly calling
> > > > the quirk functions for each device based on vendor, device and class
> > > > from early_qrk table. intel_graphics_quirks() however uses PCI_ANY_ID
> > > > and does additional filtering in the quirk.
> > > > 
> > > > If there is an Intel integrated + discrete GPU the quirk may be called
> > > > first for the discrete GPU based on the PCI topology. Then we will fail
> > > > to reserve the system stolen memory for the integrated GPU, because we
> > > > will already have marked the quirk as "applied".
> > > > 
> > > > This was reproduced in a setup with Alderlake-P (integrated) + DG2
> > > > (discrete), with the following PCI topology:
> > > > 
> > > > 	- 00:01.0 Bridge
> > > > 	  `- 03:00.0 DG2
> > > > 	- 00:02.0 Integrated GPU
> > > > 
> > > > Move the setting of quirk_applied in intel_graphics_quirks() so it's
> > > > mark as applied only when we find the integrated GPU based on the
> > > > intel_early_ids table.
> > > > 
> > > > Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
> > > 
> > > I don't know the details of stolen memory, but the implementation of
> > > this quirk looks good to me.  Very nice that it's now very clear
> > > exactly what the change is.
> > 
> > 
> > Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> > 
> > Bjorn, ack to merge through drm-intel?
> 
> This is a bit of a shared area between the x86 folks and me, but
> certainly no objection from me.

Lucas brought a good point about patch 1 touching more stuff than i915 one,
so to minimize conflicts maybe the x86 tree would be better...
also works for us if you prefer.

> 
> Acked-by: Bjorn Helgaas <bhelgaas@google.com>
> 
> > > > ---
> > > > 
> > > > v3: now that we do the refactor before the fix, we can do a single line
> > > > change to fix intel_graphics_quirks(). Also, we don't change
> > > > intel_graphics_stolen() anymore as we did in v2: we don't have to check
> > > > other devices anymore if there was a previous match causing
> > > > intel_graphics_stolen() to be called (there can only be one integrated
> > > > GPU reserving the stolen memory).
> > > > 
> > > >  arch/x86/kernel/early-quirks.c | 4 ++--
> > > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > > > 
> > > > diff --git a/arch/x86/kernel/early-quirks.c b/arch/x86/kernel/early-quirks.c
> > > > index df34963e23bf..932f9087c324 100644
> > > > --- a/arch/x86/kernel/early-quirks.c
> > > > +++ b/arch/x86/kernel/early-quirks.c
> > > > @@ -609,8 +609,6 @@ static void __init intel_graphics_quirks(int num, int slot, int func)
> > > >  	if (quirk_applied)
> > > >  		return;
> > > >  
> > > > -	quirk_applied = true;
> > > > -
> > > >  	device = read_pci_config_16(num, slot, func, PCI_DEVICE_ID);
> > > >  
> > > >  	for (i = 0; i < ARRAY_SIZE(intel_early_ids); i++) {
> > > > @@ -623,6 +621,8 @@ static void __init intel_graphics_quirks(int num, int slot, int func)
> > > >  
> > > >  		intel_graphics_stolen(num, slot, func, early_ops);
> > > >  
> > > > +		quirk_applied = true;
> > > > +
> > > >  		return;
> > > >  	}
> > > >  }
> > > > -- 
> > > > 2.34.1
> > > >