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[Qemu-devel] [PULL 1/3] vfio: Set MemoryRegionOps:max_access_size and mi
From: |
Alex Williamson |
Subject: |
[Qemu-devel] [PULL 1/3] vfio: Set MemoryRegionOps:max_access_size and min_access_size |
Date: |
Wed, 03 May 2017 15:38:57 -0600 |
User-agent: |
StGit/0.17.1-dirty |
From: Jose Ricardo Ziviani <address@hidden>
Sets valid.max_access_size and valid.min_access_size to ensure safe
8-byte accesses to vfio. Today, 8-byte accesses are broken into pairs
of 4-byte calls that goes unprotected:
qemu_mutex_lock locked mutex 0x10905ad8
vfio_region_write (0001:03:00.0:region1+0xc0, 0x2020c, 4)
qemu_mutex_unlock unlocked mutex 0x10905ad8
qemu_mutex_lock locked mutex 0x10905ad8
vfio_region_write (0001:03:00.0:region1+0xc4, 0xa0000, 4)
qemu_mutex_unlock unlocked mutex 0x10905ad8
which occasionally leads to:
qemu_mutex_lock locked mutex 0x10905ad8
vfio_region_write (0001:03:00.0:region1+0xc0, 0x2030c, 4)
qemu_mutex_unlock unlocked mutex 0x10905ad8
qemu_mutex_lock locked mutex 0x10905ad8
vfio_region_write (0001:03:00.0:region1+0xc0, 0x1000c, 4)
qemu_mutex_unlock unlocked mutex 0x10905ad8
qemu_mutex_lock locked mutex 0x10905ad8
vfio_region_write (0001:03:00.0:region1+0xc4, 0xb0000, 4)
qemu_mutex_unlock unlocked mutex 0x10905ad8
qemu_mutex_lock locked mutex 0x10905ad8
vfio_region_write (0001:03:00.0:region1+0xc4, 0xa0000, 4)
qemu_mutex_unlock unlocked mutex 0x10905ad8
causing strange errors in guest OS. With this patch, such accesses
are protected by the same lock guard:
qemu_mutex_lock locked mutex 0x10905ad8
vfio_region_write (0001:03:00.0:region1+0xc0, 0x2000c, 4)
vfio_region_write (0001:03:00.0:region1+0xc4, 0xb0000, 4)
qemu_mutex_unlock unlocked mutex 0x10905ad8
This happens because the 8-byte write should be broken into 4-byte
writes by memory.c:access_with_adjusted_size() in order to be under
the same lock. Today, it's done in exec.c:address_space_write_continue()
which was able to handle only 4 bytes due to a zero'ed
valid.max_access_size (see exec.c:memory_access_size()).
Signed-off-by: Jose Ricardo Ziviani <address@hidden>
Signed-off-by: Alex Williamson <address@hidden>
---
hw/vfio/common.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 6b33b9f55df1..6572c0744cb5 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -190,6 +190,10 @@ const MemoryRegionOps vfio_region_ops = {
.read = vfio_region_read,
.write = vfio_region_write,
.endianness = DEVICE_LITTLE_ENDIAN,
+ .valid = {
+ .min_access_size = 1,
+ .max_access_size = 8,
+ },
};
/*