Re: [PATCH v3 2/3] drm/amdkfd: force raven as "dgpu" path (v3)

[Huang Rui <ray.huang@amd.com>]

On Thu, Aug 20, 2020 at 08:31:25AM +0800, Huang Rui wrote:
> On Thu, Aug 20, 2020 at 08:18:57AM +0800, Kuehling, Felix wrote:
> > On 2020-08-19 7:56 p.m., Huang Rui wrote:
> > > On Wed, Aug 19, 2020 at 11:38:34PM +0800, Kuehling, Felix wrote:
> > >> Am 2020-08-19 um 7:06 a.m. schrieb Huang Rui:
> > >>> We still have a few iommu issues which need to address, so force raven
> > >>> as "dgpu" path for the moment.
> > >>>
> > >>> This is to add the fallback path to bypass IOMMU if IOMMU v2 is disabled
> > >>> or ACPI CRAT table not correct.
> > >>>
> > >>> v2: Use ignore_crat parameter to decide whether it will go with IOMMUv2.
> > >>> v3: Align with existed thunk, don't change the way of raven, only renoir
> > >>>      will use "dgpu" path by default.
> > >>>
> > >>> Signed-off-by: Huang Rui <ray.huang@amd.com>
> > >>> ---
> > >>>   drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c   |  5 +++-
> > >>>   drivers/gpu/drm/amd/amdkfd/kfd_crat.c     | 28 ++++++++++++++++++++++-
> > >>>   drivers/gpu/drm/amd/amdkfd/kfd_device.c   |  2 +-
> > >>>   drivers/gpu/drm/amd/amdkfd/kfd_priv.h     |  2 +-
> > >>>   drivers/gpu/drm/amd/amdkfd/kfd_topology.c |  1 +
> > >>>   5 files changed, 34 insertions(+), 4 deletions(-)
> > >>>
> > >>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> > >>> index a9a4319c24ae..189f9d7e190d 100644
> > >>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> > >>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> > >>> @@ -684,11 +684,14 @@ MODULE_PARM_DESC(debug_largebar,
> > >>>    * Ignore CRAT table during KFD initialization. By default, KFD uses the ACPI CRAT
> > >>>    * table to get information about AMD APUs. This option can serve as a workaround on
> > >>>    * systems with a broken CRAT table.
> > >>> + *
> > >>> + * Default is auto (according to asic type, iommu_v2, and crat table, to decide
> > >>> + * whehter use CRAT)
> > >>>    */
> > >>>   int ignore_crat;
> > >>>   module_param(ignore_crat, int, 0444);
> > >>>   MODULE_PARM_DESC(ignore_crat,
> > >>> -	"Ignore CRAT table during KFD initialization (0 = use CRAT (default), 1 = ignore CRAT)");
> > >>> +	"Ignore CRAT table during KFD initialization (0 = auto (default), 1 = ignore CRAT)");
> > >>>   
> > >>>   /**
> > >>>    * DOC: halt_if_hws_hang (int)
> > >>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_crat.c b/drivers/gpu/drm/amd/amdkfd/kfd_crat.c
> > >>> index 59557e3e206a..f8346d4402e2 100644
> > >>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_crat.c
> > >>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_crat.c
> > >>> @@ -22,6 +22,7 @@
> > >>>   
> > >>>   #include <linux/pci.h>
> > >>>   #include <linux/acpi.h>
> > >>> +#include <asm/processor.h>
> > >>>   #include "kfd_crat.h"
> > >>>   #include "kfd_priv.h"
> > >>>   #include "kfd_topology.h"
> > >>> @@ -740,6 +741,30 @@ static int kfd_fill_gpu_cache_info(struct kfd_dev *kdev,
> > >>>   	return 0;
> > >>>   }
> > >>>   
> > >>> +
> > >>> +#ifdef CONFIG_ACPI
> > >>> +static void kfd_setup_ignore_crat_option(void)
> > >>> +{
> > >>> +
> > >>> +	if (ignore_crat)
> > >>> +		return;
> > >>> +
> > >>> +#ifndef KFD_SUPPORT_IOMMU_V2
> > >>> +	ignore_crat = 1;
> > >>> +#else
> > >>> +	ignore_crat = 0;
> > >>> +#endif
> > >>> +
> > >>> +	/* Renoir use the fallback path to align with existed thunk */
> > >> Are you sure you need special code for Renoir here? For Renoir the
> > >> dev->device_info already treats it as a dGPU and always has.
> > > Renoir also is an APU, in other words, we might have got the correct CRAT
> > > table from SBIOS (the CRAT table in SBIOS for renoir is broken so far). If
> > > we had got CRAT table, the kfd would create an APU node. That's not
> > > expected.
> > 
> > kfd_assign_gpu will not assign a Renoir GPU as the APU from the CRAT 
> > table because gpu->device_info->needs_iommu_device is False for Renoir. 
> > So Renoir will always show up in the topology as its own discrete GPU node.
> > 
> > How does this work today? Renoir is already treated as a dGPU. But the 
> > CPU node info (/sys/class/kfd/kfd/topology/nodes/0/properties) from the 
> > CRAT table still shows GPU cores?
> > 
> 
> Yes, Renoir works well. In fact, I found the problem while I was enabling
> the dGPU path for raven before. Even I set needs_iommu_device as false in
> raven's device info. The kfd still creates the APU node. (in v1 patch)
> 
> Let me rollback to check it again.
> 

Hi Felix,

I double check it again. If Renoir's ACPI CRAT were good, we wouldn't
create virtual CRAT table for Renoir at this moement. Then the pure CPU
node is unable to be created. That conflicted with needs_iommu_device flag
(we hardcode needs_iommu_device as false for renoir). Then will break the
user mode driver. (please see below rocminfo)

rocminfo: /libhsakmt/src/topology.c:1079: topology_sysfs_get_node_props: Assertion `props->EngineId.ui32.Major' failed.

So we probably would better have a specific handling to make sure Renoir
with virtual CRAT.

Thanks,
Ray
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