This is a part of a class of related problems for qemu linux-user, in that any non-atomic store is not validated before initiating a partial write.
For instance, qemu-x86_64, built for arm32, would show this same partial store problem for any 64-bit write crossing a page boundary because we are forced by the limits of the host to split the store into two 32-bit pieces. While we could probably fix this specific case fairly easily, because it is implemented with an external helper in the first place, we would need some new infrastructure to handle the more general problem. Exactly what form that should take would need some thought and discussion. -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1785734 Title: movdqu partial write at page boundary Status in QEMU: New Bug description: In TCG mode, when a 16-byte write instruction (such as movdqu) is executed at a page boundary and causes a page fault, a partial write is executed in the first page. See the attached code for an example. Tested on the qemu-3.0.0-rc1 release. % gcc -m32 qemu-bug2.c && ./a.out && echo && qemu-i386 ./a.out [snip] page fault: addr=0x70001000 err=0x7 *(0x70000ff8+ 0) = aa *(0x70000ff8+ 1) = aa *(0x70000ff8+ 2) = aa *(0x70000ff8+ 3) = aa *(0x70000ff8+ 4) = aa *(0x70000ff8+ 5) = aa *(0x70000ff8+ 6) = aa *(0x70000ff8+ 7) = aa *(0x70000ff8+ 8) = 55 *(0x70000ff8+ 9) = 55 *(0x70000ff8+10) = 55 *(0x70000ff8+11) = 55 *(0x70000ff8+12) = 55 *(0x70000ff8+13) = 55 *(0x70000ff8+14) = 55 *(0x70000ff8+15) = 55 [snip] page fault: addr=0x70001000 err=0x6 *(0x70000ff8+ 0) = 77 *(0x70000ff8+ 1) = 66 *(0x70000ff8+ 2) = 55 *(0x70000ff8+ 3) = 44 *(0x70000ff8+ 4) = 33 *(0x70000ff8+ 5) = 22 *(0x70000ff8+ 6) = 11 *(0x70000ff8+ 7) = 0 *(0x70000ff8+ 8) = 55 *(0x70000ff8+ 9) = 55 *(0x70000ff8+10) = 55 *(0x70000ff8+11) = 55 *(0x70000ff8+12) = 55 *(0x70000ff8+13) = 55 *(0x70000ff8+14) = 55 *(0x70000ff8+15) = 55 To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1785734/+subscriptions
