[lkml]   [2019]   [Dec]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [RFC PATCH v1] devres: align strictly only for devm_kmalloc()
On Fri, Dec 20, 2019 at 03:01:03PM +0000, Robin Murphy wrote:
> On 2019-12-20 2:06 pm, Peter Zijlstra wrote:

> > data = kmalloc(size + sizeof(struct devres), GFP_KERNEL);
> At this point, you'd still need to special-case devm_kmalloc() to ensure
> size is rounded up to the next ARCH_KMALLOC_MINALIGN granule, or you'd go
> back to the original problem of the struct devres fields potentially sharing
> a cache line with the data buffer. That needs to be avoided, because if the
> devres list is modified while the buffer is mapped for noncoherent DMA
> (which could legitimately happen as they are nominally distinct allocations
> with different owners) there's liable to be data corruption one way or the
> other.

Wait up, why are you allowing non-coherent DMA at less than page size
granularity? Is that really sane? Is this really supported behaviour for
devm ?

 \ /
  Last update: 2019-12-20 18:14    [W:0.096 / U:0.552 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site