On Thu, Aug 01, 2024 at 03:44:54PM +0200, Christoph Hellwig wrote: > On Wed, Jul 31, 2024 at 06:24:24PM -0700, Nathan Chancellor wrote: > > Unfortunately, I am not sure either... I do not see anything obviously, > > so perhaps it could just be avoided with the __diag() infrastructure? > > > > diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c > > index 3dbc0b89d6fb..b58e7eb9c8f1 100644 > > --- a/kernel/dma/direct.c > > +++ b/kernel/dma/direct.c > > @@ -20,7 +20,12 @@ > > * it for entirely different regions. In that case the arch code needs to > > * override the variable below for dma-direct to work properly. > > */ > > +__diag_push(); > > +__diag_ignore(clang, 13, "-Wconstant-conversion", > > + "Clang incorrectly thinks the n == 64 case in DMA_BIT_MASK() can happen here," > > + "which would truncate with a 32-bit phys_addr_t"); > > phys_addr_t zone_dma_limit __ro_after_init = DMA_BIT_MASK(24); > > So.. The code above is clearly wrong, as DMA_BIT_MASK always returns a > u64, and phys_addr_t can be smaller than that. So at least in this case > the warning seems perfectly valid and the code has issues because it is > mixing different concepts. Sure, that seems like a reasonable way to look at things even if the warning itself is a false positive. > Where do you see warnings like this upstream? I don't see this upstream, this is from patch 2 of this series: https://lore.kernel.org/053fa4806a2c63efcde80caca473a8b670a2701c.1722249878.git.baruch@xxxxxxxxxx/ Cheers, Nathan
