thr3ads.net - Linux Virtualization - [PATCH 4/6] vhost_vdpa: support doorbell mapping via mmap [Jun 2020]

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Jason Wang

2020-Jun-03 04:18 UTC

[PATCH 4/6] vhost_vdpa: support doorbell mapping via mmap

On 2020/6/2 ??9:31, Michael S. Tsirkin wrote:> On Tue, Jun 02, 2020 at 02:49:38PM +0800, Jason Wang wrote:
>> On 2020/6/2 ??12:56, Michael S. Tsirkin wrote:
>>> On Tue, Jun 02, 2020 at 03:22:49AM +0800, kbuild test robot wrote:
>>>> Hi Jason,
>>>>
>>>> I love your patch! Yet something to improve:
>>>>
>>>> [auto build test ERROR on vhost/linux-next]
>>>> [also build test ERROR on linus/master v5.7 next-20200529]
>>>> [if your patch is applied to the wrong git tree, please drop us
a note to help
>>>> improve the system. BTW, we also suggest to use
'--base' option to specify the
>>>> base tree in git format-patch, please
seehttps://stackoverflow.com/a/37406982]
>>>>
>>>>
url:https://github.com/0day-ci/linux/commits/Jason-Wang/vDPA-doorbell-mapping/20200531-070834
>>>>
base:https://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git  linux-next
>>>> config: m68k-randconfig-r011-20200601 (attached as .config)
>>>> compiler: m68k-linux-gcc (GCC) 9.3.0
>>>> reproduce (this is a W=1 build):
>>>>          
wgethttps://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross  -O
~/bin/make.cross
>>>>           chmod +x ~/bin/make.cross
>>>>           # save the attached .config to linux build tree
>>>>           COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0
make.cross ARCH=m68k
>>>>
>>>> If you fix the issue, kindly add following tag as appropriate
>>>> Reported-by: kbuild test robot<lkp at intel.com>
>>>>
>>>> All errors (new ones prefixed by >>, old ones prefixed by
<<):
>>>>
>>>> drivers/vhost/vdpa.c: In function 'vhost_vdpa_fault':
>>>>>> drivers/vhost/vdpa.c:754:22: error: implicit
declaration of function 'pgprot_noncached'
[-Werror=implicit-function-declaration]
>>>> 754 |  vma->vm_page_prot =
pgprot_noncached(vma->vm_page_prot);
>>>> |                      ^~~~~~~~~~~~~~~~
>>>>>> drivers/vhost/vdpa.c:754:22: error: incompatible types
when assigning to type 'pgprot_t' {aka 'struct
<anonymous>'} from type 'int'
>>>> cc1: some warnings being treated as errors
>>>>
>>>> vim +/pgprot_noncached +754 drivers/vhost/vdpa.c
>>>>
>>>>      742	
>>>>      743	static vm_fault_t vhost_vdpa_fault(struct vm_fault
*vmf)
>>>>      744	{
>>>>      745		struct vhost_vdpa *v =
vmf->vma->vm_file->private_data;
>>>>      746		struct vdpa_device *vdpa = v->vdpa;
>>>>      747		const struct vdpa_config_ops *ops = vdpa->config;
>>>>      748		struct vdpa_notification_area notify;
>>>>      749		struct vm_area_struct *vma = vmf->vma;
>>>>      750		u16 index = vma->vm_pgoff;
>>>>      751	
>>>>      752		notify = ops->get_vq_notification(vdpa, index);
>>>>      753	
>>>>    > 754		vma->vm_page_prot =
pgprot_noncached(vma->vm_page_prot);
>>>>      755		if (remap_pfn_range(vma, vmf->address &
PAGE_MASK,
>>>>      756				    notify.addr >> PAGE_SHIFT, PAGE_SIZE,
>>>>      757				    vma->vm_page_prot))
>>>>      758			return VM_FAULT_SIGBUS;
>>>>      759	
>>>>      760		return VM_FAULT_NOPAGE;
>>>>      761	}
>>>>      762	
>>> Yes well, all this remapping clearly has no chance to work
>>> on systems without CONFIG_MMU.
>>
>> It looks to me mmap can work according to Documentation/nommu-mmap.txt.
But
>> I'm not sure it's worth to bother.
>>
>> Thanks
>
> Well
>
> int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
>                  unsigned long pfn, unsigned long size, pgprot_t prot)
> {
>          if (addr != (pfn << PAGE_SHIFT))
>                  return -EINVAL;
>
>          vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND |
VM_DONTDUMP;
>          return 0;
> }
> EXPORT_SYMBOL(remap_pfn_range);
>
>
> So things aren't going to work if you have a fixed PFN
> which is the case of the hardware device.

Looking at the implementation of some drivers e.g mtd_char. If I read 
the code correctly, we can do this by providing get_unmapped_area method 
and use physical address directly.

But start form CONFIG_MMU should be fine.? Do you prefer making 
vhost_vdpa depends on CONFIG_MMU or just fail mmap when CONFIG_MMU is 
not configured?

Thanks

>
>
>>>
>>>

Michael S. Tsirkin

2020-Jun-03 06:34 UTC

head link

[PATCH 4/6] vhost_vdpa: support doorbell mapping via mmap

On Wed, Jun 03, 2020 at 12:18:44PM +0800, Jason Wang
wrote:> 
> On 2020/6/2 ??9:31, Michael S. Tsirkin wrote:
> > On Tue, Jun 02, 2020 at 02:49:38PM +0800, Jason Wang wrote:
> > > On 2020/6/2 ??12:56, Michael S. Tsirkin wrote:
> > > > On Tue, Jun 02, 2020 at 03:22:49AM +0800, kbuild test robot
wrote:
> > > > > Hi Jason,
> > > > > 
> > > > > I love your patch! Yet something to improve:
> > > > > 
> > > > > [auto build test ERROR on vhost/linux-next]
> > > > > [also build test ERROR on linus/master v5.7
next-20200529]
> > > > > [if your patch is applied to the wrong git tree, please
drop us a note to help
> > > > > improve the system. BTW, we also suggest to use
'--base' option to specify the
> > > > > base tree in git format-patch, please
seehttps://stackoverflow.com/a/37406982]
> > > > > 
> > > > >
url:https://github.com/0day-ci/linux/commits/Jason-Wang/vDPA-doorbell-mapping/20200531-070834
> > > > >
base:https://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git  linux-next
> > > > > config: m68k-randconfig-r011-20200601 (attached as
.config)
> > > > > compiler: m68k-linux-gcc (GCC) 9.3.0
> > > > > reproduce (this is a W=1 build):
> > > > >          
wgethttps://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross  -O
~/bin/make.cross
> > > > >           chmod +x ~/bin/make.cross
> > > > >           # save the attached .config to linux build
tree
> > > > >           COMPILER_INSTALL_PATH=$HOME/0day
COMPILER=gcc-9.3.0 make.cross ARCH=m68k
> > > > > 
> > > > > If you fix the issue, kindly add following tag as
appropriate
> > > > > Reported-by: kbuild test robot<lkp at intel.com>
> > > > > 
> > > > > All errors (new ones prefixed by >>, old ones
prefixed by <<):
> > > > > 
> > > > > drivers/vhost/vdpa.c: In function
'vhost_vdpa_fault':
> > > > > > > drivers/vhost/vdpa.c:754:22: error: implicit
declaration of function 'pgprot_noncached'
[-Werror=implicit-function-declaration]
> > > > > 754 |  vma->vm_page_prot =
pgprot_noncached(vma->vm_page_prot);
> > > > > |                      ^~~~~~~~~~~~~~~~
> > > > > > > drivers/vhost/vdpa.c:754:22: error:
incompatible types when assigning to type 'pgprot_t' {aka 'struct
<anonymous>'} from type 'int'
> > > > > cc1: some warnings being treated as errors
> > > > > 
> > > > > vim +/pgprot_noncached +754 drivers/vhost/vdpa.c
> > > > > 
> > > > >      742	
> > > > >      743	static vm_fault_t vhost_vdpa_fault(struct
vm_fault *vmf)
> > > > >      744	{
> > > > >      745		struct vhost_vdpa *v =
vmf->vma->vm_file->private_data;
> > > > >      746		struct vdpa_device *vdpa = v->vdpa;
> > > > >      747		const struct vdpa_config_ops *ops =
vdpa->config;
> > > > >      748		struct vdpa_notification_area notify;
> > > > >      749		struct vm_area_struct *vma = vmf->vma;
> > > > >      750		u16 index = vma->vm_pgoff;
> > > > >      751	
> > > > >      752		notify = ops->get_vq_notification(vdpa,
index);
> > > > >      753	
> > > > >    > 754		vma->vm_page_prot =
pgprot_noncached(vma->vm_page_prot);
> > > > >      755		if (remap_pfn_range(vma, vmf->address
& PAGE_MASK,
> > > > >      756				    notify.addr >> PAGE_SHIFT,
PAGE_SIZE,
> > > > >      757				    vma->vm_page_prot))
> > > > >      758			return VM_FAULT_SIGBUS;
> > > > >      759	
> > > > >      760		return VM_FAULT_NOPAGE;
> > > > >      761	}
> > > > >      762	
> > > > Yes well, all this remapping clearly has no chance to work
> > > > on systems without CONFIG_MMU.
> > > 
> > > It looks to me mmap can work according to
Documentation/nommu-mmap.txt. But
> > > I'm not sure it's worth to bother.
> > > 
> > > Thanks
> > 
> > Well
> > 
> > int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
> >                  unsigned long pfn, unsigned long size, pgprot_t prot)
> > {
> >          if (addr != (pfn << PAGE_SHIFT))
> >                  return -EINVAL;
> > 
> >          vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND |
VM_DONTDUMP;
> >          return 0;
> > }
> > EXPORT_SYMBOL(remap_pfn_range);
> > 
> > 
> > So things aren't going to work if you have a fixed PFN
> > which is the case of the hardware device.
> 
> 
> Looking at the implementation of some drivers e.g mtd_char. If I read the
> code correctly, we can do this by providing get_unmapped_area method and
use
> physical address directly.
> 
> But start form CONFIG_MMU should be fine.? Do you prefer making vhost_vdpa
> depends on CONFIG_MMU or just fail mmap when CONFIG_MMU is not configured?
> 
> Thanks
I'd just not specify the mmap callback at all.
> 
> > 
> > 
> > > > 
> > > >

Jason Wang

2020-Jun-03 06:37 UTC

head link

[PATCH 4/6] vhost_vdpa: support doorbell mapping via mmap

On 2020/6/3 ??2:34, Michael S. Tsirkin wrote:> On Wed, Jun 03, 2020 at 12:18:44PM +0800, Jason Wang wrote:
>> On 2020/6/2 ??9:31, Michael S. Tsirkin wrote:
>>> On Tue, Jun 02, 2020 at 02:49:38PM +0800, Jason Wang wrote:
>>>> On 2020/6/2 ??12:56, Michael S. Tsirkin wrote:
>>>>> On Tue, Jun 02, 2020 at 03:22:49AM +0800, kbuild test robot
wrote:
>>>>>> Hi Jason,
>>>>>>
>>>>>> I love your patch! Yet something to improve:
>>>>>>
>>>>>> [auto build test ERROR on vhost/linux-next]
>>>>>> [also build test ERROR on linus/master v5.7
next-20200529]
>>>>>> [if your patch is applied to the wrong git tree, please
drop us a note to help
>>>>>> improve the system. BTW, we also suggest to use
'--base' option to specify the
>>>>>> base tree in git format-patch, please
seehttps://stackoverflow.com/a/37406982]
>>>>>>
>>>>>>
url:https://github.com/0day-ci/linux/commits/Jason-Wang/vDPA-doorbell-mapping/20200531-070834
>>>>>>
base:https://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git   linux-next
>>>>>> config: m68k-randconfig-r011-20200601 (attached as
.config)
>>>>>> compiler: m68k-linux-gcc (GCC) 9.3.0
>>>>>> reproduce (this is a W=1 build):
>>>>>>           
wgethttps://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross  -O
~/bin/make.cross
>>>>>>            chmod +x ~/bin/make.cross
>>>>>>            # save the attached .config to linux build
tree
>>>>>>            COMPILER_INSTALL_PATH=$HOME/0day
COMPILER=gcc-9.3.0 make.cross ARCH=m68k
>>>>>>
>>>>>> If you fix the issue, kindly add following tag as
appropriate
>>>>>> Reported-by: kbuild test robot<lkp at intel.com>
>>>>>>
>>>>>> All errors (new ones prefixed by >>, old ones
prefixed by <<):
>>>>>>
>>>>>> drivers/vhost/vdpa.c: In function
'vhost_vdpa_fault':
>>>>>>>> drivers/vhost/vdpa.c:754:22: error: implicit
declaration of function 'pgprot_noncached'
[-Werror=implicit-function-declaration]
>>>>>> 754 |  vma->vm_page_prot =
pgprot_noncached(vma->vm_page_prot);
>>>>>> |                      ^~~~~~~~~~~~~~~~
>>>>>>>> drivers/vhost/vdpa.c:754:22: error:
incompatible types when assigning to type 'pgprot_t' {aka 'struct
<anonymous>'} from type 'int'
>>>>>> cc1: some warnings being treated as errors
>>>>>>
>>>>>> vim +/pgprot_noncached +754 drivers/vhost/vdpa.c
>>>>>>
>>>>>>       742	
>>>>>>       743	static vm_fault_t vhost_vdpa_fault(struct
vm_fault *vmf)
>>>>>>       744	{
>>>>>>       745		struct vhost_vdpa *v =
vmf->vma->vm_file->private_data;
>>>>>>       746		struct vdpa_device *vdpa = v->vdpa;
>>>>>>       747		const struct vdpa_config_ops *ops =
vdpa->config;
>>>>>>       748		struct vdpa_notification_area notify;
>>>>>>       749		struct vm_area_struct *vma = vmf->vma;
>>>>>>       750		u16 index = vma->vm_pgoff;
>>>>>>       751	
>>>>>>       752		notify = ops->get_vq_notification(vdpa,
index);
>>>>>>       753	
>>>>>>     > 754		vma->vm_page_prot =
pgprot_noncached(vma->vm_page_prot);
>>>>>>       755		if (remap_pfn_range(vma, vmf->address
& PAGE_MASK,
>>>>>>       756				    notify.addr >> PAGE_SHIFT,
PAGE_SIZE,
>>>>>>       757				    vma->vm_page_prot))
>>>>>>       758			return VM_FAULT_SIGBUS;
>>>>>>       759	
>>>>>>       760		return VM_FAULT_NOPAGE;
>>>>>>       761	}
>>>>>>       762	
>>>>> Yes well, all this remapping clearly has no chance to work
>>>>> on systems without CONFIG_MMU.
>>>> It looks to me mmap can work according to
Documentation/nommu-mmap.txt. But
>>>> I'm not sure it's worth to bother.
>>>>
>>>> Thanks
>>> Well
>>>
>>> int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
>>>                   unsigned long pfn, unsigned long size, pgprot_t
prot)
>>> {
>>>           if (addr != (pfn << PAGE_SHIFT))
>>>                   return -EINVAL;
>>>
>>>           vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND |
VM_DONTDUMP;
>>>           return 0;
>>> }
>>> EXPORT_SYMBOL(remap_pfn_range);
>>>
>>>
>>> So things aren't going to work if you have a fixed PFN
>>> which is the case of the hardware device.
>> Looking at the implementation of some drivers e.g mtd_char. If I read
the
>> code correctly, we can do this by providing get_unmapped_area method
and use
>> physical address directly.
>>
>> But start form CONFIG_MMU should be fine.? Do you prefer making
vhost_vdpa
>> depends on CONFIG_MMU or just fail mmap when CONFIG_MMU is not
configured?
>>
>> Thanks
> I'd just not specify the mmap callback at all.

Ok, will do.

Thanks

>

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