linux-kernel - RE: [PATCH v8 1/1] crypto: add virtio-crypto driver

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Message-ID: <33183CC9F5247A488A2544077AF19020DA18F954@DGGEMA505-MBX.china.huawei.com>
Date:   Fri, 13 Jan 2017 01:56:03 +0000
From:   "Gonglei (Arei)" <arei.gonglei@...wei.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>,
        Christian Borntraeger <borntraeger@...ibm.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "qemu-devel@...gnu.org" <qemu-devel@...gnu.org>,
        "virtio-dev@...ts.oasis-open.org" <virtio-dev@...ts.oasis-open.org>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "herbert@...dor.apana.org.au" <herbert@...dor.apana.org.au>,
        "Huangweidong (C)" <weidong.huang@...wei.com>,
        Claudio Fontana <Claudio.Fontana@...wei.com>,
        Luonengjun <luonengjun@...wei.com>,
        "Hanweidong (Randy)" <hanweidong@...wei.com>,
        "Xuquan (Quan Xu)" <xuquan8@...wei.com>,
        "Wanzongshun (Vincent)" <wanzongshun@...wei.com>,
        "stefanha@...hat.com" <stefanha@...hat.com>,
        "Zhoujian (jay, Euler)" <jianjay.zhou@...wei.com>,
        longpeng <longpeng2@...wei.com>,
        "arei.gonglei@...mail.com" <arei.gonglei@...mail.com>,
        "Wubin (H)" <wu.wubin@...wei.com>
Subject: RE: [PATCH v8 1/1] crypto: add virtio-crypto driver

> 
> On Thu, Jan 12, 2017 at 03:10:25PM +0100, Christian Borntraeger wrote:
> > On 01/10/2017 01:56 PM, Christian Borntraeger wrote:
> > > 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.
> >
> >
> > any opinion on this?
> 
> Going forward, we might add an emulated aesni device and that might
> become slower than virtio. OTOH if or when this happens, we can solve it
> by adding a priority or a feature flag to virtio to raise its priority.
> 
> So I think I agree with Christian here, let's lower the priority.
> Gonglei, could you send a patch like this?
> 
OK, will do.

Thanks,
-Gonglei