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Re: [Qemu-devel] [PATCH v3 09/12] iov: add iov_get_ptr() to reference ve
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH v3 09/12] iov: add iov_get_ptr() to reference vector data |
Date: |
Thu, 22 Nov 2012 11:54:49 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:16.0) Gecko/20121016 Thunderbird/16.0.1 |
Il 22/11/2012 11:38, Michael S. Tsirkin ha scritto:
>> > The code is a little simpler, because we know the footer is 1 byte only.
>
> Yes but the APIs don't make sense in the generic case
> of >1 byte: users will have to code up two paths for when
> the buffer they want to access gets scattered across.
That would be premature optimization; with >1 byte you just use
iov_from/to_buf.
BTW, something like this function is also useful for the broken SCSI
outhdr ("the CDB starts after the common outhdr and is in a single
iovec"). But the API must be changed slightly, as in my answer to Stefan.
> If the point is to avoid scanning iov vector when data is towards the
> end of the iov, then this does sound reasonable. In that case IMHO we
> should just have accessors that work back from end of the iov. E.g.
>
> size_t iov_from_buf_end(const struct iovec *iov, unsigned int iov_cnt,
> size_t offset, const void *buf, size_t bytes)
That's also a possibility.
Paolo
- [Qemu-devel] [PATCH v3 05/12] dataplane: add event loop, (continued)
- [Qemu-devel] [PATCH v3 05/12] dataplane: add event loop, Stefan Hajnoczi, 2012/11/21
- [Qemu-devel] [PATCH v3 06/12] dataplane: add Linux AIO request queue, Stefan Hajnoczi, 2012/11/21
- [Qemu-devel] [PATCH v3 07/12] iov: add iov_discard() to remove data, Stefan Hajnoczi, 2012/11/21
- [Qemu-devel] [PATCH v3 02/12] configure: add CONFIG_VIRTIO_BLK_DATA_PLANE, Stefan Hajnoczi, 2012/11/21
- [Qemu-devel] [PATCH v3 10/12] test-iov: add iov_get_ptr() test case, Stefan Hajnoczi, 2012/11/21
- [Qemu-devel] [PATCH v3 09/12] iov: add iov_get_ptr() to reference vector data, Stefan Hajnoczi, 2012/11/21
- Re: [Qemu-devel] [PATCH v3 09/12] iov: add iov_get_ptr() to reference vector data, Stefan Hajnoczi, 2012/11/22
- Re: [Qemu-devel] [PATCH v3 09/12] iov: add iov_get_ptr() to reference vector data, Paolo Bonzini, 2012/11/22
- Re: [Qemu-devel] [PATCH v3 09/12] iov: add iov_get_ptr() to reference vector data, Michael S. Tsirkin, 2012/11/22
- Re: [Qemu-devel] [PATCH v3 09/12] iov: add iov_get_ptr() to reference vector data, Stefan Hajnoczi, 2012/11/22
[Qemu-devel] [PATCH v3 12/12] virtio-blk: add x-data-plane=on|off performance feature, Stefan Hajnoczi, 2012/11/21
[Qemu-devel] [PATCH v3 11/12] dataplane: add virtio-blk data plane code, Stefan Hajnoczi, 2012/11/21
[Qemu-devel] [PATCH v3 08/12] test-iov: add iov_discard() testcase, Stefan Hajnoczi, 2012/11/21
[Qemu-devel] [PATCH v3 03/12] dataplane: add host memory mapping code, Stefan Hajnoczi, 2012/11/21