[RFC PATCH 12/12] dma: Assert when device writes to indirect memory (such MMIO regions)

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

Assert DMA accesses are done on direct memory (in particular
to catch invalid accesses to MMIO regions).

Example with the reproducer from LP#1886362 (see previous commit):

  qemu-system-i386: include/sysemu/dma.h:111: int dma_memory_rw(AddressSpace *, dma_addr_t, void *, dma_addr_t, DMADirection, MemTxAttrs): Assertion `dir == DMA_DIRECTION_TO_DEVICE || attrs.direct_access' failed.
  (gdb) bt
  #0  0x00007ffff51d69e5 in raise () at /lib64/libc.so.6
  #1  0x00007ffff51bf895 in abort () at /lib64/libc.so.6
  #2  0x00007ffff51bf769 in _nl_load_domain.cold () at /lib64/libc.so.6
  #3  0x00007ffff51cee76 in annobin_assert.c_end () at /lib64/libc.so.6
  #4  0x0000555557b48a94 in dma_memory_rw (as=0x7fffddd3ca28, addr=4064, buf=0x7fffffff7780, len=16, dir=DMA_DIRECTION_FROM_DEVICE, attrs=...) at /home/phil/source/qemu/include/sysemu/dma.h:111
  #5  0x0000555557b487e0 in pci_dma_rw (dev=0x7fffddd3c800, addr=4064, buf=0x7fffffff7780, len=16, dir=DMA_DIRECTION_FROM_DEVICE) at /home/phil/source/qemu/include/hw/pci/pci.h:791
  #6  0x0000555557b47373 in pci_dma_write (dev=0x7fffddd3c800, addr=4064, buf=0x7fffffff7780, len=16) at /home/phil/source/qemu/include/hw/pci/pci.h:804
  #7  0x0000555557b340b4 in e1000e_write_packet_to_guest (core=0x7fffddd3f4e0, pkt=0x61100006c740, rxr=0x7fffffff7cf0, rss_info=0x7fffffff7d10) at hw/net/e1000e_core.c:1609
  #8  0x0000555557b30739 in e1000e_receive_iov (core=0x7fffddd3f4e0, iov=0x619000060e80, iovcnt=4) at hw/net/e1000e_core.c:1709
  #9  0x00005555576e2069 in e1000e_nc_receive_iov (nc=0x61400000a060, iov=0x619000060e80, iovcnt=4) at hw/net/e1000e.c:213
  #10 0x00005555572a3c34 in net_tx_pkt_sendv (pkt=0x631000028800, nc=0x61400000a060, iov=0x619000060e80, iov_cnt=4) at hw/net/net_tx_pkt.c:556
  #11 0x00005555572a23e2 in net_tx_pkt_send (pkt=0x631000028800, nc=0x61400000a060) at hw/net/net_tx_pkt.c:633
  #12 0x00005555572a4c67 in net_tx_pkt_send_loopback (pkt=0x631000028800, nc=0x61400000a060) at hw/net/net_tx_pkt.c:646
  #13 0x0000555557b70b05 in e1000e_tx_pkt_send (core=0x7fffddd3f4e0, tx=0x7fffddd5f748, queue_index=0) at hw/net/e1000e_core.c:664
  #14 0x0000555557b6eab8 in e1000e_process_tx_desc (core=0x7fffddd3f4e0, tx=0x7fffddd5f748, dp=0x7fffffff8680, queue_index=0) at hw/net/e1000e_core.c:743
  #15 0x0000555557b6d65d in e1000e_start_xmit (core=0x7fffddd3f4e0, txr=0x7fffffff88a0) at hw/net/e1000e_core.c:934
  #16 0x0000555557b5ea38 in e1000e_set_tctl (core=0x7fffddd3f4e0, index=256, val=255) at hw/net/e1000e_core.c:2431
  #17 0x0000555557b369ef in e1000e_core_write (core=0x7fffddd3f4e0, addr=1027, val=255, size=4) at hw/net/e1000e_core.c:3265
  #18 0x00005555576de3be in e1000e_mmio_write (opaque=0x7fffddd3c800, addr=1027, val=255, size=4) at hw/net/e1000e.c:109
  #19 0x0000555558e6b789 in memory_region_write_accessor (mr=0x7fffddd3f110, addr=1027, value=0x7fffffff8eb0, size=4, shift=0, mask=4294967295, attrs=...) at softmmu/memory.c:483
  #20 0x0000555558e6b05b in access_with_adjusted_size (addr=1027, value=0x7fffffff8eb0, size=1, access_size_min=4, access_size_max=4, access_fn= 0x555558e6b120 <memory_region_write_accessor>, mr=0x7fffddd3f110, attrs=...) at softmmu/memory.c:544
  #21 0x0000555558e69776 in memory_region_dispatch_write (mr=0x7fffddd3f110, addr=1027, data=255, op=MO_8, attrs=...) at softmmu/memory.c:1465
  #22 0x0000555558f60462 in flatview_write_continue (fv=0x60600003f9e0, addr=3775005699, attrs=..., ptr=0x6020000e3710, len=1, addr1=1027, l=1, mr=0x7fffddd3f110) at exec.c:3176
  #23 0x0000555558f4e38b in flatview_write (fv=0x60600003f9e0, addr=3775005699, attrs=..., buf=0x6020000e3710, len=1) at exec.c:3220
  #24 0x0000555558f4dd4f in address_space_write (as=0x60800000baa0, addr=3775005699, attrs=..., buf=0x6020000e3710, len=1) at exec.c:3315
  #25 0x000055555916b3e0 in qtest_process_command (chr=0x55555c03f300 <qtest_chr>, words=0x604000058150) at softmmu/qtest.c:567
  #26 0x000055555915f7f2 in qtest_process_inbuf (chr=0x55555c03f300 <qtest_chr>, inbuf=0x6190000200e0) at softmmu/qtest.c:710

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 include/sysemu/dma.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/sysemu/dma.h b/include/sysemu/dma.h
index 8a7dbf0b0f3..a4ba9438a56 100644
--- a/include/sysemu/dma.h
+++ b/include/sysemu/dma.h
@@ -108,6 +108,8 @@ static inline int dma_memory_rw(AddressSpace *as, dma_addr_t addr,
                                 void *buf, dma_addr_t len,
                                 DMADirection dir, MemTxAttrs attrs)
 {
+    assert(dir == DMA_DIRECTION_TO_DEVICE || attrs.direct_access);
+
     dma_barrier(as, dir);
 
     return dma_memory_rw_relaxed(as, addr, buf, len, dir, attrs);
-- 
2.26.2