Hi Sagi, I wander what's the performance overhead with this DIF support? And is there a roadmap for support SRP/ISER and target side for DIF?
Regards, Jack On 10/31/2013 01:24 PM, Sagi Grimberg wrote: > This patchset Introduces Verbs level support for signature handover > feature. Siganture is intended to implement end-to-end data integrity > on a transactional basis in a completely offloaded manner. > > There are several end-to-end data integrity methods used today in various > applications and/or upper layer protocols such as T10-DIF defined by SCSI > specifications (SBC), CRC32, XOR8 and more. This patchset adds verbs > support only for T10-DIF. The proposed framework allows adding more > signature methods in the future. > > In T10-DIF, when a series of 512-byte data blocks are transferred, each > block is followed by an 8-byte guard. The guard consists of CRC that > protects the integrity of the data in the block, and some other tags > that protects against mis-directed IOs. > > Data can be protected when transferred over the wire, but can also be > protected in the memory of the sender/receiver. This allows true end- > to-end protection against bits flipping either over the wire, through > gateways, in memory, over PCI, etc. > > While T10-DIF clearly defines that over the wire protection guards are > interleaved into the data stream (each 512-Byte block followed by 8-byte > guard), when in memory, the protection guards may reside in a buffer > separated from the data. Depending on the application, it is usually > easier to handle the data when it is contiguous. In this case the data > buffer will be of size 512xN and the protection buffer will be of size > 8xN (where N is the number of blocks in the transaction). > > There are 3 kinds of signature handover operation: > 1. Take unprotected data (from wire or memory) and ADD protection > guards. > 2. Take protetected data (from wire or memory), validate the data > integrity against the protection guards and STRIP the protection > guards. > 3. Take protected data (from wire or memory), validate the data > integrity against the protection guards and PASS the data with > the guards as-is. > > This translates to defining to the HCA how/if data protection exists > in memory domain, and how/if data protection exists is wire domain. > > The way that data integrity is performed is by using a new kind of > memory region: signature-enabled MR, and a new kind of work request: > REG_SIG_MR. The REG_SIG_MR WR operates on the signature-enabled MR, > and defines all the needed information for the signature handover > (data buffer, protection buffer if needed and signature attributes). > The result is an MR that can be used for data transfer as usual, > that will also add/validate/strip/pass protection guards. > > When the data transfer is successfully completed, it does not mean > that there are no integrity errors. The user must afterwards check > the signature status of the handover operation using a new light-weight > verb. > > This feature shall be used in storage upper layer protocols iSER/SRP > implementing end-to-end data integrity T10-DIF. Following this patchset, > we will soon submit krping patches which will demonstrate the usage of > these signature verbs. > -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
