On Thu, Mar 2, 2023 at 7:34 PM Stefano Garzarella <sgarzare@xxxxxxxxxx> wrote: > > kmap_atomic() is deprecated in favor of kmap_local_page(). It's better to mention the commit or code that introduces this. > > With kmap_local_page() the mappings are per thread, CPU local, can take > page-faults, and can be called from any context (including interrupts). > Furthermore, the tasks can be preempted and, when they are scheduled to > run again, the kernel virtual addresses are restored and still valid. > > kmap_atomic() is implemented like a kmap_local_page() which also disables > page-faults and preemption (the latter only for !PREEMPT_RT kernels, > otherwise it only disables migration). > > The code within the mappings/un-mappings in getu16_iotlb() and > putu16_iotlb() don't depend on the above-mentioned side effects of > kmap_atomic(), Note we used to use spinlock to protect simulators (at least until patch 7, so we probably need to re-order the patches at least) so I think this is only valid when: The vringh IOTLB helpers are not used in atomic context (e.g spinlock, interrupts). If yes, should we document this? (Or should we introduce a boolean to say whether an IOTLB variant can be used in an atomic context)? Thanks > so that mere replacements of the old API with the new one > is all that is required (i.e., there is no need to explicitly add calls > to pagefault_disable() and/or preempt_disable()). > > Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx> > --- > > Notes: > v2: > - added this patch since checkpatch.pl complained about deprecation > of kmap_atomic() touched by next patch > > drivers/vhost/vringh.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c > index a1e27da54481..0ba3ef809e48 100644 > --- a/drivers/vhost/vringh.c > +++ b/drivers/vhost/vringh.c > @@ -1220,10 +1220,10 @@ static inline int getu16_iotlb(const struct vringh *vrh, > if (ret < 0) > return ret; > > - kaddr = kmap_atomic(iov.bv_page); > + kaddr = kmap_local_page(iov.bv_page); > from = kaddr + iov.bv_offset; > *val = vringh16_to_cpu(vrh, READ_ONCE(*(__virtio16 *)from)); > - kunmap_atomic(kaddr); > + kunmap_local(kaddr); > > return 0; > } > @@ -1241,10 +1241,10 @@ static inline int putu16_iotlb(const struct vringh *vrh, > if (ret < 0) > return ret; > > - kaddr = kmap_atomic(iov.bv_page); > + kaddr = kmap_local_page(iov.bv_page); > to = kaddr + iov.bv_offset; > WRITE_ONCE(*(__virtio16 *)to, cpu_to_vringh16(vrh, val)); > - kunmap_atomic(kaddr); > + kunmap_local(kaddr); > > return 0; > } > -- > 2.39.2 >
