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    SubjectRe: [PATCH v2 3/8] vringh: replace kmap_atomic() with kmap_local_page()
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    On giovedì 2 marzo 2023 12:34:16 CET Stefano Garzarella wrote:
    > kmap_atomic() is deprecated in favor of kmap_local_page().
    >
    > 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(), 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()).

    It seems that my commit message is quite clear and complete and therefore has
    already been reused by others who have somehow given me credit.

    I would really appreciate it being mentioned here that you are reusing a
    "boiler plate" commit message of my own making and Cc me :-)

    Thanks,

    Fabio

    > Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
    > ---
    >
    > 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




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