On 06.09.14 04:49, Alexey Kardashevskiy wrote:
> At the moment VFIO's BARs are NATIVE_ENDIAN. The idea is that since
> it does not parse BARs content and just provides transport, it should
> not do byte swaps, the guest does it anyway. That worked fine while
> the host was big-endian and it does not work when the host is little-endian.
> This happens because ./configure defines static macro TARGET_WORDS_BIGENDIAN
> for ppc64 and since there is no ppc64le - endianness of host and guest does
> not match and stl_p&co swaps bytes as shown below.
>
> The proposed patch at the end of this mail fixes the issue for VFIO in
> any combination of host-guest, BE-LE (need to double check with BE host).
> However since I fail to grasp the idea of having statically defined
> TARGET_WORDS_BIGENDIAN, I assume I am missing something big here.
>
> What would the correct fix be here? Thanks!
>
>
>
> Breakpoint 9, vfio_bar_read (opaque=0x10de2e98, addr=0x6f4, size=0x4) at
> /home/alexey/p/qemu/hw/misc/vfio.c:1140
> 1140 {
> Missing separate debuginfos, use: zypper install
> glibc-debuginfo-2.19-15.1.ppc64le
> libgcc_s1-debuginfo-4.8.3+r212056-4.17.ppc64le
> libglib-2_0-0-debuginfo-2.38.2-5.8.ppc64le libgthread-2_0-0-debu
> ginfo-2.38.2-5.8.ppc64le libpcre1-debuginfo-8.33-3.253.ppc64le
> libpixman-1-0-debuginfo-0.32.6-1.1.ppc64le
> libstdc++6-debuginfo-4.8.3+r212056-4.17.ppc64le
> libz1-debuginfo-1.2.8-4.65.ppc64le
> (gdb) bt
> #0 vfio_bar_read (opaque=0x10de2e98, addr=0x6f4, size=0x4) at
> /home/alexey/p/qemu/hw/misc/vfio.c:1140
> #1 0x00000000100a4bd4 in memory_region_read_accessor (mr=0x10de2ea8,
> addr=0x6f4, value=0x3fffb77de320, size=0x4, shift=0x0, mask=0xffffffff) at
> /home/alexey/p/qemu/memory.c:410
> #2 0x00000000100a5000 in access_with_adjusted_size (addr=0x6f4,
> value=0x3fffb77de320, size=0x4, access_size_min=0x1, access_size_max=0x4,
> access=0x100a4b38 <memory_region_read_accessor>, mr=0x1
> 0de2ea8) at /home/alexey/p/qemu/memory.c:475
> #3 0x00000000100a84ac in memory_region_dispatch_read1 (mr=0x10de2ea8,
> addr=0x6f4, size=0x4) at /home/alexey/p/qemu/memory.c:1097
> #4 0x00000000100a85d8 in memory_region_dispatch_read (mr=0x10de2ea8,
> addr=0x6f4, pval=0x3fffb77de458, size=0x4) at
> /home/alexey/p/qemu/memory.c:1119
> #5 0x00000000100ace24 in io_mem_read (mr=0x10de2ea8, addr=0x6f4,
> pval=0x3fffb77de458, size=0x4) at /home/alexey/p/qemu/memory.c:1967
> #6 0x0000000010013bf8 in address_space_rw (as=0x1081d410
> <address_space_memory>, addr=0x1a0b00006f4, buf=0x3fffb7f80028 "", len=0x4,
> is_write=0x0) at /home/alexey/p/qemu/exec.c:2076
> #7 0x0000000010013fa4 in cpu_physical_memory_rw (addr=0x1a0b00006f4,
> buf=0x3fffb7f80028 "", len=0x4, is_write=0x0) at
> /home/alexey/p/qemu/exec.c:2121
> #8 0x00000000100a015c in kvm_cpu_exec (cpu=0x3fffb77e0010) at
> /home/alexey/p/qemu/kvm-all.c:1770
> #9 0x000000001007ab18 in qemu_kvm_cpu_thread_fn (arg=0x3fffb77e0010) at
> /home/alexey/p/qemu/cpus.c:940
> #10 0x00003fffb7828a64 in start_thread () from /lib64/libpthread.so.0
> #11 0x00003fffb7993b00 in clone () from /lib64/libc.so.6
> (gdb) n
> 1141 VFIOBAR *bar = opaque;
> (gdb)
> 1148 uint64_t data = 0;
> (gdb)
> 1150 if (pread(bar->fd, &buf, size, bar->fd_offset + addr) != size) {
> (gdb)
> 1156 switch (size) {
> (gdb)
> 1164 data = buf.dword;
> (gdb)
> 1165 break;
> (gdb)
> 1171 if (addr == 0x6f4) {
> (gdb)
> 1172 printf("%s %u size=%d val=%lx\n", __func__, __LINE__, size,
> data);
> (gdb)
> vfio_bar_read 1172 size=4 val=4
> 1187 vfio_eoi(container_of(bar, VFIODevice, bars[bar->nr]));
> (gdb)
> 1189 return data;
> (gdb)
> 1190 }
> (gdb)
> memory_region_read_accessor (mr=0x10de2ea8, addr=0x6f4, value=0x3fffb77de320,
> size=0x4, shift=0x0, mask=0xffffffff) at /home/alexey/p/qemu/memory.c:411
> 411 trace_memory_region_ops_read(mr, addr, tmp, size);
> (gdb)
> 412 *value |= (tmp & mask) << shift;
> (gdb)
> 413 }
> (gdb)
> access_with_adjusted_size (addr=0x6f4, value=0x3fffb77de320, size=0x4,
> access_size_min=0x1, access_size_max=0x4, access=0x100a4b38
> <memory_region_read_accessor>, mr=0x10de2ea8) at /home/alexey/p
> /qemu/memory.c:474
> 474 for (i = 0; i < size; i += access_size) {
> (gdb)
> 483 }
> (gdb)
> memory_region_dispatch_read1 (mr=0x10de2ea8, addr=0x6f4, size=0x4) at
> /home/alexey/p/qemu/memory.c:1106
> 1106 return data;
> (gdb)
> 1107 }
> (gdb)
> memory_region_dispatch_read (mr=0x10de2ea8, addr=0x6f4, pval=0x3fffb77de458,
> size=0x4) at /home/alexey/p/qemu/memory.c:1120
> 1120 adjust_endianness(mr, pval, size);
> (gdb) s
> adjust_endianness (mr=0x10de2ea8, data=0x3fffb77de458, size=0x4) at
> /home/alexey/p/qemu/memory.c:364
> 364 {
> (gdb) n
> 365 if (memory_region_wrong_endianness(mr)) {
> (gdb)
> 382 }
> (gdb)
> memory_region_dispatch_read (mr=0x10de2ea8, addr=0x6f4, pval=0x3fffb77de458,
> size=0x4) at /home/alexey/p/qemu/memory.c:1121
> 1121 return false;
> (gdb)
> 1122 }
> (gdb)
> io_mem_read (mr=0x10de2ea8, addr=0x6f4, pval=0x3fffb77de458, size=0x4) at
> /home/alexey/p/qemu/memory.c:1968
> 1968 }
> (gdb)
> address_space_rw (as=0x1081d410 <address_space_memory>, addr=0x1a0b00006f4,
> buf=0x3fffb7f80028 "", len=0x4, is_write=0x0) at
> /home/alexey/p/qemu/exec.c:2077
> 2077 stl_p(buf, val);
How do you end up in stl_p on an mmio read? That sounds odd.
Alex
