ef5bc96268
The following sequence happens: - the SeaBIOS virtio-blk driver does not support the WCE feature, which causes QEMU to disable writeback caching - the Linux virtio-blk driver resets the device, finds WCE is available but writeback caching is disabled; tells block layer to not send cache flush commands - the Linux virtio-blk driver sets the DRIVER_OK bit, which causes writeback caching to be re-enabled, but the Linux virtio-blk driver does not know of this side effect and cache flushes remain disabled The bug is at the third step. If the guest does know about CONFIG_WCE, QEMU should ignore the WCE feature's state. The guest will control the cache mode solely using configuration space. This change makes Linux do flushes correctly, but Linux will keep SeaBIOS's writethrough mode. Hence, whenever the guest is reset, the cache mode of the disk should be reset to whatever was specified in the "-drive" option. With this change, the Linux virtio-blk driver finds that writeback caching is enabled, and tells the block layer to send cache flush commands appropriately. Reported-by: Rusty Russell <rusty@au1.ibm.com Cc: qemu-stable@nongnu.org Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
155 lines
4.4 KiB
C
155 lines
4.4 KiB
C
/*
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* Virtio Block Device
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*
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* Copyright IBM, Corp. 2007
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*
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* Authors:
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* Anthony Liguori <aliguori@us.ibm.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2. See
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* the COPYING file in the top-level directory.
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*
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*/
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#ifndef _QEMU_VIRTIO_BLK_H
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#define _QEMU_VIRTIO_BLK_H
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#include "hw/virtio/virtio.h"
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#include "hw/block/block.h"
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#define TYPE_VIRTIO_BLK "virtio-blk-device"
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#define VIRTIO_BLK(obj) \
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OBJECT_CHECK(VirtIOBlock, (obj), TYPE_VIRTIO_BLK)
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/* from Linux's linux/virtio_blk.h */
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/* The ID for virtio_block */
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#define VIRTIO_ID_BLOCK 2
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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 /* Indicates support of legacy geometry */
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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_IDENTIFY 8 ATA IDENTIFY supported, DEPRECATED */
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#define VIRTIO_BLK_F_WCE 9 /* write cache enabled */
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#define VIRTIO_BLK_F_TOPOLOGY 10 /* Topology information is available */
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#define VIRTIO_BLK_F_CONFIG_WCE 11 /* write cache configurable */
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#define VIRTIO_BLK_ID_BYTES 20 /* ID string length */
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struct virtio_blk_config
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{
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uint64_t capacity;
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uint32_t size_max;
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uint32_t seg_max;
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uint16_t cylinders;
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uint8_t heads;
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uint8_t sectors;
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uint32_t blk_size;
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uint8_t physical_block_exp;
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uint8_t alignment_offset;
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uint16_t min_io_size;
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uint32_t opt_io_size;
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uint8_t wce;
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} QEMU_PACKED;
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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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/* Flush the volatile write cache */
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#define VIRTIO_BLK_T_FLUSH 4
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/* return the device ID string */
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#define VIRTIO_BLK_T_GET_ID 8
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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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{
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/* VIRTIO_BLK_T* */
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uint32_t type;
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/* io priority. */
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uint32_t ioprio;
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/* Sector (ie. 512 byte offset) */
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uint64_t sector;
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};
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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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/* This is the last element of the write scatter-gather list */
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struct virtio_blk_inhdr
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{
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unsigned char status;
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};
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/* SCSI pass-through header */
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struct virtio_scsi_inhdr
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{
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uint32_t errors;
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uint32_t data_len;
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uint32_t sense_len;
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uint32_t residual;
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};
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struct VirtIOBlkConf
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{
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BlockConf conf;
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char *serial;
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uint32_t scsi;
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uint32_t config_wce;
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uint32_t data_plane;
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};
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struct VirtIOBlockDataPlane;
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typedef struct VirtIOBlock {
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VirtIODevice parent_obj;
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BlockDriverState *bs;
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VirtQueue *vq;
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void *rq;
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QEMUBH *bh;
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BlockConf *conf;
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VirtIOBlkConf blk;
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unsigned short sector_mask;
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bool original_wce;
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VMChangeStateEntry *change;
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#ifdef CONFIG_VIRTIO_BLK_DATA_PLANE
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Notifier migration_state_notifier;
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struct VirtIOBlockDataPlane *dataplane;
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#endif
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} VirtIOBlock;
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#define DEFINE_VIRTIO_BLK_FEATURES(_state, _field) \
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DEFINE_VIRTIO_COMMON_FEATURES(_state, _field)
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#ifdef __linux__
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#define DEFINE_VIRTIO_BLK_PROPERTIES(_state, _field) \
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DEFINE_BLOCK_PROPERTIES(_state, _field.conf), \
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DEFINE_BLOCK_CHS_PROPERTIES(_state, _field.conf), \
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DEFINE_PROP_STRING("serial", _state, _field.serial), \
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DEFINE_PROP_BIT("config-wce", _state, _field.config_wce, 0, true), \
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DEFINE_PROP_BIT("scsi", _state, _field.scsi, 0, true)
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#else
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#define DEFINE_VIRTIO_BLK_PROPERTIES(_state, _field) \
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DEFINE_BLOCK_PROPERTIES(_state, _field.conf), \
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DEFINE_BLOCK_CHS_PROPERTIES(_state, _field.conf), \
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DEFINE_PROP_STRING("serial", _state, _field.serial), \
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DEFINE_PROP_BIT("config-wce", _state, _field.config_wce, 0, true)
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#endif /* __linux__ */
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void virtio_blk_set_conf(DeviceState *dev, VirtIOBlkConf *blk);
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#endif
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