diff options
| -rw-r--r-- | blockdev.c | 6 | ||||
| -rw-r--r-- | hmp-commands.hx | 5 | ||||
| -rw-r--r-- | qemu-config.c | 4 | ||||
| -rw-r--r-- | qemu-options.hx | 9 |
4 files changed, 21 insertions, 3 deletions
diff --git a/blockdev.c b/blockdev.c index 9068c5b1d0..af4e239b93 100644 --- a/blockdev.c +++ b/blockdev.c @@ -257,6 +257,7 @@ DriveInfo *drive_init(QemuOpts *opts, int default_to_scsi) DriveInfo *dinfo; BlockIOLimit io_limits; int snapshot = 0; + bool copy_on_read; int ret; translation = BIOS_ATA_TRANSLATION_AUTO; @@ -273,6 +274,7 @@ DriveInfo *drive_init(QemuOpts *opts, int default_to_scsi) snapshot = qemu_opt_get_bool(opts, "snapshot", 0); ro = qemu_opt_get_bool(opts, "readonly", 0); + copy_on_read = qemu_opt_get_bool(opts, "copy-on-read", false); file = qemu_opt_get(opts, "file"); serial = qemu_opt_get(opts, "serial"); @@ -546,6 +548,10 @@ DriveInfo *drive_init(QemuOpts *opts, int default_to_scsi) bdrv_flags |= (BDRV_O_SNAPSHOT|BDRV_O_CACHE_WB|BDRV_O_NO_FLUSH); } + if (copy_on_read) { + bdrv_flags |= BDRV_O_COPY_ON_READ; + } + if (media == MEDIA_CDROM) { /* CDROM is fine for any interface, don't check. */ ro = 1; diff --git a/hmp-commands.hx b/hmp-commands.hx index f8d855e3be..79a919526d 100644 --- a/hmp-commands.hx +++ b/hmp-commands.hx @@ -860,9 +860,10 @@ ETEXI .args_type = "pci_addr:s,opts:s", .params = "[[<domain>:]<bus>:]<slot>\n" "[file=file][,if=type][,bus=n]\n" - "[,unit=m][,media=d][index=i]\n" + "[,unit=m][,media=d][,index=i]\n" "[,cyls=c,heads=h,secs=s[,trans=t]]\n" - "[snapshot=on|off][,cache=on|off]", + "[,snapshot=on|off][,cache=on|off]\n" + "[,readonly=on|off][,copy-on-read=on|off]", .help = "add drive to PCI storage controller", .mhandler.cmd = drive_hot_add, }, diff --git a/qemu-config.c b/qemu-config.c index 1aa080fbcb..18f30204a1 100644 --- a/qemu-config.c +++ b/qemu-config.c @@ -109,6 +109,10 @@ static QemuOptsList qemu_drive_opts = { .name = "bps_wr", .type = QEMU_OPT_NUMBER, .help = "limit write bytes per second", + },{ + .name = "copy-on-read", + .type = QEMU_OPT_BOOL, + .help = "copy read data from backing file into image file", }, { /* end of list */ } }, diff --git a/qemu-options.hx b/qemu-options.hx index 25a7be7948..b3db10c0ad 100644 --- a/qemu-options.hx +++ b/qemu-options.hx @@ -135,7 +135,7 @@ DEF("drive", HAS_ARG, QEMU_OPTION_drive, " [,cyls=c,heads=h,secs=s[,trans=t]][,snapshot=on|off]\n" " [,cache=writethrough|writeback|none|directsync|unsafe][,format=f]\n" " [,serial=s][,addr=A][,id=name][,aio=threads|native]\n" - " [,readonly=on|off]\n" + " [,readonly=on|off][,copy-on-read=on|off]\n" " [[,bps=b]|[[,bps_rd=r][,bps_wr=w]]][[,iops=i]|[[,iops_rd=r][,iops_wr=w]]\n" " use 'file' as a drive image\n", QEMU_ARCH_ALL) STEXI @@ -187,6 +187,9 @@ host disk is full; report the error to the guest otherwise). The default setting is @option{werror=enospc} and @option{rerror=report}. @item readonly Open drive @option{file} as read-only. Guest write attempts will fail. +@item copy-on-read=@var{copy-on-read} +@var{copy-on-read} is "on" or "off" and enables whether to copy read backing +file sectors into the image file. @end table By default, writethrough caching is used for all block device. This means that @@ -218,6 +221,10 @@ like your host losing power, the disk storage getting disconnected accidently, etc. you're image will most probably be rendered unusable. When using the @option{-snapshot} option, unsafe caching is always used. +Copy-on-read avoids accessing the same backing file sectors repeatedly and is +useful when the backing file is over a slow network. By default copy-on-read +is off. + Instead of @option{-cdrom} you can use: @example qemu -drive file=file,index=2,media=cdrom |