[igt-dev] [PATCH i-g-t 2/2] lib/intel_batchbuffer: Limit intel-bb to 48-bit va

[Zbigniew Kempczyński]

On Mon, May 15, 2023 at 09:18:59PM +0200, Kamil Konieczny wrote:
> Hi Zbigniew,
> 
> On 2023-05-11 at 21:36:17 +0200, Zbigniew Kempczyński wrote:
> > On PVC Xe returns 57-bit va bit size. Unfortunately MI_* commands are
> > limited to 48-bit, so we should provide offsets which are within this
> > range and won't produce page faults like:
> > 
> > <4> [781.114047] xe 0000:8c:00.0: [drm]
> > 	ASID: 1196
> > 	VFID: 0
> > 	PDATA: 0x00a3
> > 	Faulted Address: 0x0000ffffffff0000
> > 	FaultType: 0
> > 	AccessType: 0
> > 	FaultLevel: 4
> > 	EngineClass: 3
> > 	EngineInstance: 0
> > <4> [781.144174] xe 0000:8c:00.0: [drm] Fault response: Unsuccessful -22
> > 
> > Lets alter intel-bb with default (SIMPLE allocator, HIGH_TO_LOW strategy)
> > to omit 48-57 bit addressing by setting end of va range to 48-bit max.
> > 
> > Signed-off-by: Zbigniew Kempczyński <zbigniew.kempczynski at intel.com>
> > ---
> >  lib/intel_batchbuffer.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> > 
> > diff --git a/lib/intel_batchbuffer.c b/lib/intel_batchbuffer.c
> > index 14ed8057e8..58ba28498a 100644
> > --- a/lib/intel_batchbuffer.c
> > +++ b/lib/intel_batchbuffer.c
> > @@ -937,7 +937,10 @@ __intel_bb_create(int fd, uint32_t ctx, const intel_ctx_cfg_t *cfg,
> >  		ibb->alignment = xe_get_default_alignment(fd);
> >  		size = ALIGN(size, ibb->alignment);
> >  		ibb->handle = xe_bo_create_flags(fd, 0, size, vram_if_possible(fd, 0));
> > -		ibb->gtt_size = 1ull << xe_va_bits(fd);
> > +
> > +		/* Limit to 48-bit due to MI_* address limitation */
> 
> Looks like igt_debug_once would be usefull here.

I wanted to avoid conditional constructs here (only for altered
va ranges makes sense adding debugging). Code is clear here imo,
we truncate to 48bit (max) regardless platform.

I'll pick r-b without changing the code if you don't mind.

--
Zbigniew

> 
> Reviewed-by: Kamil Konieczny <kamil.konieczny at linux.intel.com>
> 
> --
> Kamil
> 
> > +		ibb->gtt_size = 1ull << min_t(uint32_t, xe_va_bits(fd), 48);
> > +		end = ibb->gtt_size;
> >  
> >  		if (!ctx)
> >  			ctx = xe_vm_create(fd, DRM_XE_VM_CREATE_ASYNC_BIND_OPS, 0);
> > -- 
> > 2.34.1
> >