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a718978ed5
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John Snow a718978ed5 ide: add limit to .prepare_buf() 
prepare_buf should not always grab as many descriptors
as it can, sometimes it should self-limit.

For example, an NCQ transfer of 1 sector with a PRDT that
describes 4GiB of data should not copy 4GiB of data, it
should just transfer that first 512 bytes.

PIO is not affected, because the dma_buf_rw dma helpers
already have a byte limit built-in to them, but DMA/NCQ
will exhaust the entire list regardless of requested size.

AHCI 1.3 specifies in section 6.1.6 Command List Underflow that
NCQ is not required to detect underflow conditions. Non-NCQ
pathways signal underflow by writing to the PRDBC field, which
will already occur by writing the actual transferred byte count
to the PRDBC, signaling the underflow.

Our NCQ pathways aren't required to detect underflow, but since our DMA
backend uses the size of the PRDT to determine the size of the transer,
if our PRDT is bigger than the transaction (the underflow condition) it
doesn't cost us anything to detect it and truncate the PRDT.

This is a recoverable error and is not signaled to the guest, in either
NCQ or normal DMA cases.

For BMDMA, the existing pathways should see no guest-visible difference,
but any bytes described in the overage will no longer be transferred
before indicating to the guest that there was an underflow.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 1435767578-32743-2-git-send-email-jsnow@redhat.com
2015-07-04 02:06:04 -04:00
audio qerror: Move #include out of qerror.h 2015-06-22 18:20:40 +02:00
backends Include qapi/qmp/qerror.h exactly where needed 2015-06-22 18:20:41 +02:00
block block: remove redundant check before g_slist_find() 2015-07-02 10:06:23 +01:00
bsd-user target-i386: use memory API to implement SMRAM 2015-06-05 17:36:39 +02:00
default-configs virtio-gpu: pci support bits and virtio-vga. 2015-06-16 10:35:43 +01:00
disas target-mips: add MTHC0 and MFHC0 instructions 2015-06-12 09:05:31 +01:00
docs update pci-bridge-seat section in docs/multiseat.txt 2015-07-03 12:21:11 +02:00
dtc@65cc4d2748 dtc: Update dtc / libfdt submodule to version 1.4.0 2015-06-03 23:56:49 +02:00
fpu target-s390x: define default NaN values 2015-06-05 01:37:58 +02:00
fsdev virtfs-proxy-helper: fail gracefully if socket path is too long 2015-06-16 20:32:29 +05:30
gdb-xml gdb-xml: Include XML for s390 vector registers 2015-05-27 17:52:03 +02:00
hw ide: add limit to .prepare_buf() 2015-07-04 02:06:04 -04:00
include virtio-input: add input routing support 2015-07-03 12:21:11 +02:00
libcacard libcacard: pkgconfig: tidy dependent libs 2015-06-23 19:57:28 +03:00
libdecnumber remove libdecnumber/dpd/decimal128Local.h 2015-06-23 19:57:27 +03:00
linux-headers virtio, pci fixes, enhancements 2015-06-19 11:30:57 +01:00
linux-user linux-user: ioctl() command type is int 2015-06-16 09:37:17 +03:00
migration Include monitor/monitor.h exactly where needed 2015-06-22 18:20:41 +02:00
net net: simplify net_client_init1() 2015-06-24 16:33:42 +01:00
pc-bios s390-ccw.img: update 2015-06-30 09:34:58 +02:00
pixman@87eea99e44
po
qapi qmp: Add optional bool "unmap" to drive-mirror 2015-07-02 10:06:23 +01:00
qga qerror: Clean up QERR_ macros to expand into a single string 2015-06-22 18:20:40 +02:00
qobject Include qapi/qmp/qerror.h exactly where needed 2015-06-22 18:20:41 +02:00
qom qerror: Clean up QERR_ macros to expand into a single string 2015-06-22 18:20:40 +02:00
roms Update OpenBIOS images 2015-06-17 20:02:15 +01:00
scripts Include qapi/qmp/qerror.h exactly where needed 2015-06-22 18:20:41 +02:00
slirp qerror: Move #include out of qerror.h 2015-06-22 18:20:40 +02:00
stubs Include qapi/qmp/qerror.h exactly where needed 2015-06-22 18:20:41 +02:00
target-alpha disas: Remove uses of CPU env 2015-06-22 17:40:01 +02:00
target-arm target-arm: A64: Print ELR when taking exceptions 2015-06-26 14:22:36 +01:00
target-cris disas: Remove uses of CPU env 2015-06-22 17:40:01 +02:00
target-i386 Include qapi/qmp/qerror.h exactly where needed 2015-06-22 18:20:41 +02:00
target-lm32 disas: Remove uses of CPU env 2015-06-22 17:40:01 +02:00
target-m68k m68k: remove useless parameter op_size from gen_lea_indexed() 2015-06-29 17:11:57 +02:00
target-microblaze disas: Remove uses of CPU env 2015-06-22 17:40:01 +02:00
target-mips target-mips: add mips32r6-generic CPU definition 2015-06-26 09:22:26 +01:00
target-moxie target-moxie: Fix warnings from Sparse (one-bit signed bitfield) 2015-03-19 11:11:55 +03:00
target-openrisc disas: Remove uses of CPU env 2015-06-22 17:40:01 +02:00
target-ppc disas: Remove uses of CPU env 2015-06-22 17:40:01 +02:00
target-s390x s390x/gdb: synchronize cpu state after modifying acrs 2015-07-02 15:35:33 +02:00
target-sh4 disas: Remove uses of CPU env 2015-06-22 17:40:01 +02:00
target-sparc disas: Remove uses of CPU env 2015-06-22 17:40:01 +02:00
target-tricore target-tricore: fix depositing bits from PCXI into ICR 2015-06-29 14:02:58 +02:00
target-unicore32 disas: Remove uses of CPU env 2015-06-22 17:40:01 +02:00
target-xtensa disas: Remove uses of CPU env 2015-06-22 17:40:01 +02:00
tcg tcg/optimize: rename tcg_constant_folding 2015-06-09 07:00:56 -07:00
tests qtest/ahci: ncq migration test 2015-07-04 02:06:04 -04:00
trace Remove superfluous '\n' around error_report() 2015-03-10 08:15:33 +03:00
ui Include monitor/monitor.h exactly where needed 2015-06-22 18:20:41 +02:00
util timer: Use a single definition of NSEC_PER_SEC for the whole codebase 2015-07-02 09:20:18 +01:00
.exrc
.gitignore gitignore: Ignore more .pod files. 2015-04-04 09:45:59 +03:00
.gitmodules
.mailmap
.travis.yml
accel.c
aio-posix.c AioContext: acquire/release AioContext during aio_poll 2015-04-28 15:36:08 +02:00
aio-win32.c AioContext: acquire/release AioContext during aio_poll 2015-04-28 15:36:08 +02:00
arch_init.c migration: reduce include files 2015-06-12 06:42:34 +02:00
async.c Revert "iothread: release iothread around aio_poll" 2015-06-12 13:58:33 +01:00
balloon.c Include monitor/monitor.h exactly where needed 2015-06-22 18:20:41 +02:00
block.c block: Remove bdrv_reset_dirty 2015-07-02 10:06:23 +01:00
blockdev-nbd.c Include monitor/monitor.h exactly where needed 2015-06-22 18:20:41 +02:00
blockdev.c qmp: Add optional bool "unmap" to drive-mirror 2015-07-02 10:06:23 +01:00
blockjob.c Include qapi/qmp/qerror.h exactly where needed 2015-06-22 18:20:41 +02:00
bootdevice.c misc: fix typos in copyright declaration 2015-03-26 14:21:43 +01:00
bt-host.c
bt-vhci.c
Changelog
CODING_STYLE
configure block/iscsi: restore compatiblity with libiscsi 1.9.0 2015-07-02 10:06:23 +01:00
COPYING
COPYING.LIB
coroutine-gthread.c
coroutine-sigaltstack.c
coroutine-ucontext.c
coroutine-win32.c
cpu-exec.c
cpus.c qerror: Move #include out of qerror.h 2015-06-22 18:20:40 +02:00
cputlb.c memory: replace cpu_physical_memory_reset_dirty() with test-and-clear 2015-06-05 17:10:00 +02:00
device_tree.c device-tree: Make a common-obj 2015-06-03 14:21:24 +03:00
device-hotplug.c pci-hotplug-old: Has been dead for five major releases, bury 2015-03-01 12:37:54 +01:00
disas.c disas: Remove uses of CPU env 2015-06-22 17:40:01 +02:00
dma-helpers.c range: remove useless inclusions 2015-04-30 16:05:48 +03:00
dump.c Include qapi/qmp/qerror.h exactly where needed 2015-06-22 18:20:41 +02:00
exec.c exec: clamp accesses against the MemoryRegionSection 2015-06-19 12:27:14 +02:00
gdbstub.c semihosting: create SemihostingConfig structure and semihost.h 2015-06-19 14:17:45 +01:00
HACKING
hmp-commands.hx qmp/hmp: add rocker device support 2015-06-12 13:42:17 +01:00
hmp.c qmp: Add optional bool "unmap" to drive-mirror 2015-07-02 10:06:23 +01:00
hmp.h qmp/hmp: add rocker device support 2015-06-12 13:42:17 +01:00
iohandler.c iohandler: Change return type of qemu_set_fd_handler to "void" 2015-06-12 13:26:21 +01:00
ioport.c - miscellaneous cleanups for TCG (Emilio) and NBD (Bogdan) 2015-04-30 12:04:11 +01:00
iothread.c qom: Add helper function for getting user objects root 2015-06-19 18:40:00 +02:00
kvm-all.c kvm: remove special handling of DIRTY_MEMORY_MIGRATION in the dirty log mask 2015-06-05 17:09:59 +02:00
kvm-stub.c
LICENSE
main-loop.c Change qemu_set_fd_handler2(..., NULL, ...) to qemu_set_fd_handler 2015-06-12 13:26:21 +01:00
MAINTAINERS virtio, pci fixes, enhancements 2015-06-26 15:57:43 +01:00
Makefile Makefile: Add "make ctags" 2015-06-23 20:23:39 +03:00
Makefile.objs device-tree: Make a common-obj 2015-06-03 14:21:24 +03:00
Makefile.target migration: move savevm.c inside migration/ 2015-06-12 06:42:30 +02:00
memory_mapping.c
memory.c memory: use mr->ram_addr in "is this RAM?" assertions 2015-06-05 17:10:00 +02:00
module-common.c
monitor.c Include qapi/qmp/qerror.h exactly where needed 2015-06-22 18:20:41 +02:00
nbd.c qemu-nbd: only send a limited number of errno codes on the wire 2015-05-08 14:45:11 +02:00
numa.c Include qapi/qmp/qerror.h exactly where needed 2015-06-22 18:20:41 +02:00
os-posix.c rcu: do not create thread in pthread_atfork callback 2015-04-01 10:06:38 +02:00
os-win32.c
page_cache.c
qapi-schema.json s390x/kvm/watchdog 2015-06-15 13:24:51 +01:00
qdev-monitor.c Include qapi/qmp/qerror.h exactly where needed 2015-06-22 18:20:41 +02:00
qdict-test-data.txt
qemu-bridge-helper.c
qemu-char.c qerror: Move #include out of qerror.h 2015-06-22 18:20:40 +02:00
qemu-coroutine-io.c coroutine-io: Return -errno in case of error 2015-03-18 12:07:21 +01:00
qemu-coroutine-lock.c coroutine: remove unnecessary parentheses in qemu_co_queue_empty 2015-04-30 16:05:49 +03:00
qemu-coroutine-sleep.c
qemu-coroutine.c coroutine: Clean up qemu_coroutine_enter() 2015-03-09 11:11:59 +01:00
qemu-doc.texi raw-posix: Deprecate host floppy passthrough 2015-03-19 11:43:02 +01:00
qemu-img-cmds.hx
qemu-img.c Include qapi/qmp/qerror.h exactly where needed 2015-06-22 18:20:41 +02:00
qemu-img.texi
qemu-io-cmds.c qerror: Move #include out of qerror.h 2015-06-22 18:20:40 +02:00
qemu-io.c qerror: Move #include out of qerror.h 2015-06-22 18:20:40 +02:00
qemu-log.c
qemu-nbd.c qerror: Move #include out of qerror.h 2015-06-22 18:20:40 +02:00
qemu-nbd.texi
qemu-options-wrapper.h
qemu-options.h
qemu-options.hx block/iscsi: restore compatiblity with libiscsi 1.9.0 2015-07-02 10:06:23 +01:00
qemu-seccomp.c
qemu-tech.texi
qemu-timer.c qemu-timer: Call clock reset notifiers on forward jumps 2015-06-19 12:27:14 +02:00
qemu.nsi
qemu.sasl
qjson.c QJSON: Use OBJECT_CHECK 2015-05-11 08:59:07 -04:00
qmp-commands.hx qmp: Add optional bool "unmap" to drive-mirror 2015-07-02 10:06:23 +01:00
qmp.c Include monitor/monitor.h exactly where needed 2015-06-22 18:20:41 +02:00
qtest.c qtest: pre-buffer hex nibs 2015-05-22 15:58:22 -04:00
README
rules.mak rules.mak: Force CFLAGS for all objects in DSO 2015-05-08 14:45:11 +02:00
softmmu_template.h softmmu: Add probe_write() 2015-06-11 10:13:28 +01:00
spice-qemu-char.c spice: fix spice_chr_add_watch() pre-condition 2015-05-29 09:56:01 +02:00
tcg-runtime.c
tci.c tcg: Mask TCGMemOp appropriately for indexing 2015-06-09 06:35:29 -07:00
thread-pool.c thread-pool: clean up thread_pool_completion_bh() 2015-04-28 15:36:09 +02:00
thunk.c linux-user: Allocate thunk size dynamically 2015-06-15 11:36:58 +03:00
tpm.c Include monitor/monitor.h exactly where needed 2015-06-22 18:20:41 +02:00
trace-events ossaudio: use trace events instead of debug config flag 2015-06-15 12:42:48 +02:00
translate-all.c translate-all: fix watchpoints if retranslation not possible 2015-06-17 12:40:52 +02:00
translate-all.h translate-all: remove unnecessary argument to tb_invalidate_phys_range 2015-06-05 17:09:59 +02:00
user-exec.c exec: move functions to translate-all.h 2015-06-05 17:09:59 +02:00
VERSION Open 2.4 development tree 2015-04-25 22:05:07 +01:00
version.rc
vl.c qerror: Move #include out of qerror.h 2015-06-22 18:20:40 +02:00
xen-common-stub.c
xen-common.c
xen-hvm-stub.c xen: Remove xen_cmos_set_s3_resume() 2015-03-10 08:15:33 +03:00
xen-hvm.c xen-220615, more SOB lines 2015-06-23 17:46:20 +01:00
xen-mapcache.c

README 

Read the documentation in qemu-doc.html or on http://wiki.qemu-project.org

- QEMU team