Re: [PATCH 3/5] drm/amdgpu: Paper over the drm_driver mangling for virt

[Luben Tuikov <luben.tuikov@amd.com>]

On 2020-10-30 08:04, Daniel Vetter wrote:
> On Fri, Oct 30, 2020 at 11:41 AM Liu, Monk <Monk.Liu@amd.com> wrote:
>>
>> [AMD Official Use Only - Internal Distribution Only]
>>
>> What's the purpose of the patch sets
>>
>> e.g.: what bug can those 5 patches fix or what feature provided
>>
>> for this particular one (3/5) I didn't see how it helpful, could you give a background  ?
> 
> It's good to make function tables const, so that they can be write
> protected. More resilience against exploits and all that. This patch
> here is needed to be able to make drm_device->driver const so that all
> other drivers can make their drm_driver structure const. Would be good
> to fully fix up amdgpu like in the comment, but I'm not going that in
> this series here.
> -Daniel

Hi Daniel,

I feel that that's a good change.

But if you can clarify this for me... Is this leading
towards a single instance of a struct drm_driver per
low-level driver, i.e. amdgpu?

And as such, being able to be defined as const?

So that we have many GPU devices driven by one
low-level driver (amdgpu_drv), represented by one
const drm_driver (and thus const)?

Which would imply that if varied devices can be handled
by a single low-level driver, whose struct drm_driver
settings cannot be shared among subset of devices (say
very old and new), then the low-level driver
would have to create more than one "const" struct drm_driver?

Regards,
Luben

> 
>>
>> thanks
>> _____________________________________
>> Monk Liu|GPU Virtualization Team |AMD
>>
>>
>> -----Original Message-----
>> From: Daniel Vetter <daniel.vetter@ffwll.ch>
>> Sent: Friday, October 30, 2020 6:11 PM
>> To: DRI Development <dri-devel@lists.freedesktop.org>
>> Cc: Intel Graphics Development <intel-gfx@lists.freedesktop.org>; Daniel Vetter <daniel.vetter@ffwll.ch>; Deucher, Alexander <Alexander.Deucher@amd.com>; Koenig, Christian <Christian.Koenig@amd.com>; Quan, Evan <Evan.Quan@amd.com>; Kuehling, Felix <Felix.Kuehling@amd.com>; Zhang, Hawking <Hawking.Zhang@amd.com>; Grodzovsky, Andrey <Andrey.Grodzovsky@amd.com>; Tuikov, Luben <Luben.Tuikov@amd.com>; Thomas Zimmermann <tzimmermann@suse.de>; Liu, Monk <Monk.Liu@amd.com>; Yintian Tao <yttao@amd.com>; Li, Dennis <Dennis.Li@amd.com>; Liu, Shaoyun <Shaoyun.Liu@amd.com>; Zhang, Bokun <Bokun.Zhang@amd.com>; Yang, Stanley <Stanley.Yang@amd.com>; Sheng, Wenhui <Wenhui.Sheng@amd.com>; Gong, Curry <Curry.Gong@amd.com>; Daniel Vetter <daniel.vetter@intel.com>
>> Subject: [PATCH 3/5] drm/amdgpu: Paper over the drm_driver mangling for virt
>>
>> Prep work to make drm_device->driver const.
>>
>> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
>> Cc: Alex Deucher <alexander.deucher@amd.com>
>> Cc: "Christian König" <christian.koenig@amd.com>
>> Cc: Evan Quan <evan.quan@amd.com>
>> Cc: Felix Kuehling <Felix.Kuehling@amd.com>
>> Cc: Hawking Zhang <Hawking.Zhang@amd.com>
>> Cc: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
>> Cc: Luben Tuikov <luben.tuikov@amd.com>
>> Cc: Thomas Zimmermann <tzimmermann@suse.de>
>> Cc: Monk Liu <Monk.Liu@amd.com>
>> Cc: Yintian Tao <yttao@amd.com>
>> Cc: Dennis Li <Dennis.Li@amd.com>
>> Cc: shaoyunl <shaoyun.liu@amd.com>
>> Cc: Bokun Zhang <Bokun.Zhang@amd.com>
>> Cc: "Stanley.Yang" <Stanley.Yang@amd.com>
>> Cc: Wenhui Sheng <Wenhui.Sheng@amd.com>
>> Cc: chen gong <curry.gong@amd.com>
>> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
>> ---
>>  drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c  |  8 ++++----  drivers/gpu/drm/amd/amdgpu/amdgpu_virt.c | 12 +++++++++++-
>>  2 files changed, 15 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>> index 024c3b70b1aa..3d337f13ae4e 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>> @@ -1093,7 +1093,7 @@ static const struct pci_device_id pciidlist[] = {
>>
>>  MODULE_DEVICE_TABLE(pci, pciidlist);
>>
>> -static struct drm_driver kms_driver;
>> +struct drm_driver amdgpu_kms_driver;
>>
>>  static int amdgpu_pci_probe(struct pci_dev *pdev,
>>      const struct pci_device_id *ent) @@ -1164,7 +1164,7 @@ static int amdgpu_pci_probe(struct pci_dev *pdev,
>>  if (ret)
>>  return ret;
>>
>> -adev = devm_drm_dev_alloc(&pdev->dev, &kms_driver, typeof(*adev), ddev);
>> +adev = devm_drm_dev_alloc(&pdev->dev, &amdgpu_kms_driver,
>> +typeof(*adev), ddev);
>>  if (IS_ERR(adev))
>>  return PTR_ERR(adev);
>>
>> @@ -1508,7 +1508,7 @@ int amdgpu_file_to_fpriv(struct file *filp, struct amdgpu_fpriv **fpriv)
>>  return 0;
>>  }
>>
>> -static struct drm_driver kms_driver = {
>> +struct drm_driver amdgpu_kms_driver = {
>>  .driver_features =
>>      DRIVER_ATOMIC |
>>      DRIVER_GEM |
>> @@ -1571,7 +1571,7 @@ static int __init amdgpu_init(void)
>>  goto error_fence;
>>
>>  DRM_INFO("amdgpu kernel modesetting enabled.\n");
>> -kms_driver.num_ioctls = amdgpu_max_kms_ioctl;
>> +amdgpu_kms_driver.num_ioctls = amdgpu_max_kms_ioctl;
>>  amdgpu_register_atpx_handler();
>>
>>  /* Ignore KFD init failures. Normal when CONFIG_HSA_AMD is not set. */ diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_virt.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_virt.c
>> index d0aea5e39531..dde4c449c284 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_virt.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_virt.c
>> @@ -45,13 +45,23 @@ bool amdgpu_virt_mmio_blocked(struct amdgpu_device *adev)
>>  return RREG32_NO_KIQ(0xc040) == 0xffffffff;  }
>>
>> +extern struct drm_driver amdgpu_kms_driver;
>> +
>>  void amdgpu_virt_init_setting(struct amdgpu_device *adev)  {
>>  /* enable virtual display */
>>  if (adev->mode_info.num_crtc == 0)
>>  adev->mode_info.num_crtc = 1;
>>  adev->enable_virtual_display = true;
>> -adev_to_drm(adev)->driver->driver_features &= ~DRIVER_ATOMIC;
>> +
>> +/*
>> + * FIXME: Either make virt support atomic or make sure you have two
>> + * drm_driver structs, these kind of tricks are only ok when there's
>> + * guaranteed only a single device per system. This should also be done
>> + * before struct drm_device is initialized.
>> + */
>> +amdgpu_kms_driver.driver_features &= ~DRIVER_ATOMIC;
>> +
>>  adev->cg_flags = 0;
>>  adev->pg_flags = 0;
>>  }
>> --
>> 2.28.0
>>
> 
> 

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