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Re: [PATCH v8 1/1] crypto: add virtio-crypto driver

From Christian Borntraeger <borntraeger@de.ibm.com>
Newsgroups linux.kernel
Subject Re: [PATCH v8 1/1] crypto: add virtio-crypto driver
Date 2017-01-10 14:00 +0100
Message-ID <sY4bT-1qK-5@gated-at.bofh.it> (permalink)
References <sOtEB-8g3-1@gated-at.bofh.it> <sOtOi-8jg-13@gated-at.bofh.it> <sY3IS-1gX-7@gated-at.bofh.it> <sY3Sx-1k3-1@gated-at.bofh.it>
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On 01/10/2017 01:36 PM, Gonglei (Arei) wrote:
> Hi,
> 
>>
>> On 12/15/2016 03:03 AM, Gonglei wrote:
>> [...]
>>> +
>>> +static struct crypto_alg virtio_crypto_algs[] = { {
>>> +	.cra_name = "cbc(aes)",
>>> +	.cra_driver_name = "virtio_crypto_aes_cbc",
>>> +	.cra_priority = 501,
>>
>>
>> This is still higher than the hardware-accelerators (like intel aesni or the
>> s390 cpacf functions or the arm hw). aesni and s390/cpacf are supported by the
>> hardware virtualization and available to the guests. I do not see a way how
>> virtio
>> crypto can be faster than that (in the end it might be cpacf/aesni + overhead)
>> instead it will very likely be slower.
>> So we should use a number that is higher than software implementations but
>> lower than the hw ones.
>>
>> Just grepping around, the software ones seem be be around 100 and the
>> hardware
>> ones around 200-400. So why was 150 not enough?
>>
> I didn't find a documentation about how we use the priority, and I assumed
> people use virtio-crypto will configure hardware accelerators in the
> host. So I choosed the number which bigger than aesni's priority.

Yes, but the aesni driver will only bind if there is HW support in the guest.
And if aesni is available in the guest (or the s390 aes function from cpacf)
it will always be faster than the same in the host via virtio.So your priority
should be smaller.

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Thread

Re: [PATCH v8 1/1] crypto: add virtio-crypto driver Christian Borntraeger <borntraeger@de.ibm.com> - 2017-01-10 13:30 +0100
  RE: [PATCH v8 1/1] crypto: add virtio-crypto driver "Gonglei (Arei)" <arei.gonglei@huawei.com> - 2017-01-10 13:40 +0100
    Re: [PATCH v8 1/1] crypto: add virtio-crypto driver Christian Borntraeger <borntraeger@de.ibm.com> - 2017-01-10 14:00 +0100
      Re: [PATCH v8 1/1] crypto: add virtio-crypto driver Christian Borntraeger <borntraeger@de.ibm.com> - 2017-01-12 15:20 +0100
        Re: [PATCH v8 1/1] crypto: add virtio-crypto driver "Michael S. Tsirkin" <mst@redhat.com> - 2017-01-12 15:30 +0100
          RE: [PATCH v8 1/1] crypto: add virtio-crypto driver "Gonglei (Arei)" <arei.gonglei@huawei.com> - 2017-01-13 03:00 +0100

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