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Subject: Re: [External] [PATCH v3 4/5] virtio-crypto: adjust dst_len at ops
 callback
From:   =?utf-8?B?5L2V56OK?= <helei.sig11@bytedance.com>
In-Reply-To: <4edf9c3d37f1435a8a6701a7429a3aba@huawei.com>
Date:   Fri, 22 Apr 2022 14:58:33 +0800
Cc:     =?utf-8?B?5L2V56OK?= <helei.sig11@bytedance.com>,
        zhenwei pi <pizhenwei@bytedance.com>,
        "mst@redhat.com" <mst@redhat.com>,
        "jasowang@redhat.com" <jasowang@redhat.com>,
        "herbert@gondor.apana.org.au" <herbert@gondor.apana.org.au>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "virtualization@lists.linux-foundation.org" 
        <virtualization@lists.linux-foundation.org>,
        "linux-crypto@vger.kernel.org" <linux-crypto@vger.kernel.org>,
        "davem@davemloft.net" <davem@davemloft.net>
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Message-Id: <7B16C43E-1C25-44B6-A4F0-B546935ECA27@bytedance.com>
References: <20220421104016.453458-1-pizhenwei@bytedance.com>
 <20220421104016.453458-5-pizhenwei@bytedance.com>
 <4edf9c3d37f1435a8a6701a7429a3aba@huawei.com>
To:     "Gonglei (Arei)" <arei.gonglei@huawei.com>
Precedence: bulk


> On Apr 21, 2022, at 9:46 PM, Gonglei (Arei) <arei.gonglei@huawei.com> =
wrote:
>=20
>=20
>=20
>> -----Original Message-----
>> From: zhenwei pi [mailto:pizhenwei@bytedance.com]
>> Sent: Thursday, April 21, 2022 6:40 PM
>> To: Gonglei (Arei) <arei.gonglei@huawei.com>; mst@redhat.com
>> Cc: jasowang@redhat.com; herbert@gondor.apana.org.au;
>> linux-kernel@vger.kernel.org; =
virtualization@lists.linux-foundation.org;
>> linux-crypto@vger.kernel.org; helei.sig11@bytedance.com;
>> davem@davemloft.net; zhenwei pi <pizhenwei@bytedance.com>
>> Subject: [PATCH v3 4/5] virtio-crypto: adjust dst_len at ops callback
>>=20
>> From: lei he <helei.sig11@bytedance.com>
>>=20
>> For some akcipher operations(eg, decryption of pkcs1pad(rsa)), the =
length of
>> returned result maybe less than akcipher_req->dst_len, we need to =
recalculate
>> the actual dst_len through the virt-queue protocol.
>>=20
> OK ...
>=20
>> Cc: Michael S. Tsirkin <mst@redhat.com>
>> Cc: Jason Wang <jasowang@redhat.com>
>> Cc: Gonglei <arei.gonglei@huawei.com>
>> Signed-off-by: lei he <helei.sig11@bytedance.com>
>> Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
>> ---
>> drivers/crypto/virtio/virtio_crypto_akcipher_algs.c | 5 ++++-
>> 1 file changed, 4 insertions(+), 1 deletion(-)
>>=20
>> diff --git a/drivers/crypto/virtio/virtio_crypto_akcipher_algs.c
>> b/drivers/crypto/virtio/virtio_crypto_akcipher_algs.c
>> index 9561bc2df62b..82db86e088c2 100644
>> --- a/drivers/crypto/virtio/virtio_crypto_akcipher_algs.c
>> +++ b/drivers/crypto/virtio/virtio_crypto_akcipher_algs.c
>> @@ -90,9 +90,12 @@ static void
>> virtio_crypto_dataq_akcipher_callback(struct virtio_crypto_request *
>> 	}
>>=20
>> 	akcipher_req =3D vc_akcipher_req->akcipher_req;
>> -	if (vc_akcipher_req->opcode !=3D VIRTIO_CRYPTO_AKCIPHER_VERIFY)
>> +	if (vc_akcipher_req->opcode !=3D VIRTIO_CRYPTO_AKCIPHER_VERIFY) =
{
>> +		/* actuall length maybe less than dst buffer */
>> +		akcipher_req->dst_len =3D len - sizeof(vc_req->status);
>=20
> ...but why minus sizeof(vc_req->status)?

The len here indicates the total length of data written by the device. =
for encrypt/decrypt/sign,
the virt crypto device writes two parts of data: dst_data and =
status(virtio_crypto_inhdr).=20
To obtain dst_len, the size of status needs to be subtracted.

>=20
>=20
> Regards,
> -Gonglei