Michael,
On Sat, Feb 05, 2022 at 02:41:31PM +0000, Michael Kelley (LINUX) wrote:
> From: Vitaly Chikunov <vt@xxxxxxxxxxxx> Sent: Friday, February 4, 2022 8:06 PM
> >
> > On Fri, Feb 04, 2022 at 04:10:49PM +0000, Michael Kelley (LINUX) wrote:
> > > From: Vitaly Chikunov <vt@xxxxxxxxxxxx> Sent: Friday, February 4, 2022 5:05 AM
> > > >
> > > > Clang 12.0.1 cannot understand that value 64 is excluded from the shift
> > > > at compile time (for use in global context) resulting in build error:
> > > >
> > > > drivers/hv/vmbus_drv.c:2082:29: error: shift count >= width of type [-Werror,-
> > > > Wshift-count-overflow]
> > > > static u64 vmbus_dma_mask = DMA_BIT_MASK(64);
> > > > ^~~~~~~~~~~~~~~~
> > > > ./include/linux/dma-mapping.h:76:54: note: expanded from macro 'DMA_BIT_MASK'
> > > > #define DMA_BIT_MASK(n) (((n) == 64) ? ~0ULL : ((1ULL<<(n))-1))
> > > > ^ ~~~
> > > >
> > > > Avoid using DMA_BIT_MASK macro for that corner case.
> > > >
> > > > Cc: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>
> > > > Cc: Michael Kelley <mikelley@xxxxxxxxxxxxx>
> > > > Cc: Long Li <longli@xxxxxxxxxxxxx>
> > > > Cc: Wei Liu <wei.liu@xxxxxxxxxx>
> > > > Signed-off-by: Vitaly Chikunov <vt@xxxxxxxxxxxx>
> > > > ---
> > > > drivers/hv/vmbus_drv.c | 3 ++-
> > > > 1 file changed, 2 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> > > > index 17bf55fe3169..a1306ca15d3f 100644
> > > > --- a/drivers/hv/vmbus_drv.c
> > > > +++ b/drivers/hv/vmbus_drv.c
> > > > @@ -2079,7 +2079,8 @@ struct hv_device *vmbus_device_create(const guid_t *type,
> > > > return child_device_obj;
> > > > }
> > > >
> > > > -static u64 vmbus_dma_mask = DMA_BIT_MASK(64);
> > > > +/* Use ~0ULL instead of DMA_BIT_MASK(64) to work around a bug in Clang. */
> > > > +static u64 vmbus_dma_mask = ~0ULL;
> > > > /*
> > > > * vmbus_device_register - Register the child device
> > > > */
> > > > --
> > > > 2.33.0
> > >
> > > Instead of the hack approach, does the following code rearrangement solve
> > > the problem by eliminating the use of DMA_BIT_MASK(64) in a static initializer?
> > > I don't have Clang handy to try it.
> >
> > Yes this compiles well on Clang.
> >
> > Vitaly,
> >
>
> Do you want to submit a patch with my approach, or should I do it? I'm
> happy to do it, but I don't want to pre-empt what you have already
> started without your OK.
I'm OK if you send it!
Thanks,
>
> Michael
>
> > >
> > > This approach also more closely follows the pattern used in other device types.
> > >
> > > Michael
> > >
> > >
> > > diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> > > index 17bf55f..0d96634 100644
> > > --- a/drivers/hv/vmbus_drv.c
> > > +++ b/drivers/hv/vmbus_drv.c
> > > @@ -2079,7 +2079,6 @@ struct hv_device *vmbus_device_create(const guid_t
> > *type,
> > > return child_device_obj;
> > > }
> > >
> > > -static u64 vmbus_dma_mask = DMA_BIT_MASK(64);
> > > /*
> > > * vmbus_device_register - Register the child device
> > > */
> > > @@ -2120,8 +2119,9 @@ int vmbus_device_register(struct hv_device
> > *child_device_obj)
> > > }
> > > hv_debug_add_dev_dir(child_device_obj);
> > >
> > > - child_device_obj->device.dma_mask = &vmbus_dma_mask;
> > > child_device_obj->device.dma_parms = &child_device_obj->dma_parms;
> > > + child_device_obj->device.dma_mask = &child_device_obj->dma_mask;
> > > + dma_set_mask(&child_device_obj->device, DMA_BIT_MASK(64));
> > > return 0;
> > >
> > > err_kset_unregister:
> > > diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
> > > index f565a89..fe2e017 100644
> > > --- a/include/linux/hyperv.h
> > > +++ b/include/linux/hyperv.h
> > > @@ -1262,6 +1262,7 @@ struct hv_device {
> > > struct vmbus_channel *channel;
> > > struct kset *channels_kset;
> > > struct device_dma_parameters dma_parms;
> > > + u64 dma_mask;
> > >
> > > /* place holder to keep track of the dir for hv device in debugfs */
> > > struct dentry *debug_dir;
