linux-kernel - Re: [PATCH v2 3/8] vringh: replace kmap_atomic() with kmap_local

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Message-ID: <20230316091752.vskzw5trzz772s3n@sgarzare-redhat>
Date:   Thu, 16 Mar 2023 10:17:52 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     "Fabio M. De Francesco" <fmdefrancesco@...il.com>
Cc:     virtualization@...ts.linux-foundation.org,
        Andrey Zhadchenko <andrey.zhadchenko@...tuozzo.com>,
        eperezma@...hat.com, netdev@...r.kernel.org, stefanha@...hat.com,
        linux-kernel@...r.kernel.org, Jason Wang <jasowang@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>, kvm@...r.kernel.org
Subject: Re: [PATCH v2 3/8] vringh: replace kmap_atomic() with
 kmap_local_page()

On Thu, Mar 16, 2023 at 10:13:39AM +0100, Fabio M. De Francesco wrote:
>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 :-)

Yes of course, sorry for not doing this previously!

Thanks,
Stefano