69740c8ba8
Allow reading various alignment values from the config page. This allows the guest to much better align I/O requests depending on the storage topology. Note that the formats for the config values appear a bit messed up, but we follow the formats used by ATA and SCSI so they are expected in the storage world. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
95 lines
2.8 KiB
C
95 lines
2.8 KiB
C
#ifndef _LINUX_VIRTIO_BLK_H
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#define _LINUX_VIRTIO_BLK_H
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/* This header is BSD licensed so anyone can use the definitions to implement
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* compatible drivers/servers. */
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#include <linux/types.h>
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#include <linux/virtio_ids.h>
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#include <linux/virtio_config.h>
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/* Feature bits */
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#define VIRTIO_BLK_F_BARRIER 0 /* Does host support barriers? */
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#define VIRTIO_BLK_F_SIZE_MAX 1 /* Indicates maximum segment size */
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#define VIRTIO_BLK_F_SEG_MAX 2 /* Indicates maximum # of segments */
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#define VIRTIO_BLK_F_GEOMETRY 4 /* Legacy geometry available */
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#define VIRTIO_BLK_F_RO 5 /* Disk is read-only */
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#define VIRTIO_BLK_F_BLK_SIZE 6 /* Block size of disk is available*/
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#define VIRTIO_BLK_F_SCSI 7 /* Supports scsi command passthru */
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#define VIRTIO_BLK_F_FLUSH 9 /* Cache flush command support */
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#define VIRTIO_BLK_F_TOPOLOGY 10 /* Topology information is available */
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struct virtio_blk_config {
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/* The capacity (in 512-byte sectors). */
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__u64 capacity;
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/* The maximum segment size (if VIRTIO_BLK_F_SIZE_MAX) */
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__u32 size_max;
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/* The maximum number of segments (if VIRTIO_BLK_F_SEG_MAX) */
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__u32 seg_max;
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/* geometry the device (if VIRTIO_BLK_F_GEOMETRY) */
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struct virtio_blk_geometry {
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__u16 cylinders;
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__u8 heads;
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__u8 sectors;
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} geometry;
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/* block size of device (if VIRTIO_BLK_F_BLK_SIZE) */
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__u32 blk_size;
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/* the next 4 entries are guarded by VIRTIO_BLK_F_TOPOLOGY */
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/* exponent for physical block per logical block. */
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__u8 physical_block_exp;
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/* alignment offset in logical blocks. */
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__u8 alignment_offset;
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/* minimum I/O size without performance penalty in logical blocks. */
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__u16 min_io_size;
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/* optimal sustained I/O size in logical blocks. */
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__u32 opt_io_size;
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} __attribute__((packed));
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/*
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* Command types
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*
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* Usage is a bit tricky as some bits are used as flags and some are not.
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*
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* Rules:
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* VIRTIO_BLK_T_OUT may be combined with VIRTIO_BLK_T_SCSI_CMD or
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* VIRTIO_BLK_T_BARRIER. VIRTIO_BLK_T_FLUSH is a command of its own
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* and may not be combined with any of the other flags.
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*/
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/* These two define direction. */
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#define VIRTIO_BLK_T_IN 0
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#define VIRTIO_BLK_T_OUT 1
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/* This bit says it's a scsi command, not an actual read or write. */
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#define VIRTIO_BLK_T_SCSI_CMD 2
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/* Cache flush command */
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#define VIRTIO_BLK_T_FLUSH 4
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/* Barrier before this op. */
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#define VIRTIO_BLK_T_BARRIER 0x80000000
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/* This is the first element of the read scatter-gather list. */
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struct virtio_blk_outhdr {
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/* VIRTIO_BLK_T* */
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__u32 type;
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/* io priority. */
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__u32 ioprio;
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/* Sector (ie. 512 byte offset) */
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__u64 sector;
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};
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struct virtio_scsi_inhdr {
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__u32 errors;
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__u32 data_len;
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__u32 sense_len;
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__u32 residual;
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};
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/* And this is the final byte of the write scatter-gather list. */
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#define VIRTIO_BLK_S_OK 0
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#define VIRTIO_BLK_S_IOERR 1
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#define VIRTIO_BLK_S_UNSUPP 2
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#endif /* _LINUX_VIRTIO_BLK_H */
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