On 12/31/14 17:23, Paolo Bonzini wrote: > > > On 31/12/2014 16:17, Peter Maydell wrote: >> On 31 December 2014 at 14:07, Laszlo Ersek <ler...@redhat.com> wrote: >>>> Of course this also renders the issue mostly moot -- if none of us can >>>> test the code on a BE host, then that use case simply doesn't exist in >>>> practice. >> If you can give me a test image and a command line I can test >> it on one of the PPC64 boxes in the GCC compile farm. > > You can follow the qtest steps in the commit messages of > 6c87e3d5967a1d731b5f591a8f0ee6c319c14ca8: > > $ arm-softmmu/qemu-system-arm -M virt -machine accel=qtest \ > -qtest stdio -uuid 4600cb32-38ec-4b2f-8acb-81c6ea54f2d8 > writew 0x9020008 0x0200 > readl 0x9020000 > > The readl should return "OK 0x000000004600cb32".
The -uuid switch parses the UUID string with qemu_uuid_parse() into the qemu_uuid array, and the first four bytes are stored with "%02hhx%02hhx%02hhx%02hhx"; ie. byte-wise. The fw_cfg_init1() function adds these bytes as a string (== saves a reference to qemu_uuid), with fw_cfg_add_bytes(). Good. I looked at the "readl" command implementation in qtest_process_command(). I don't know what it intends to do. *If* it prints the number that the guest CPU sees immediately when it performs the wide read, then it should print 0x0000000032cb0046, on both big and little endian hosts; assuming a little endian guest. Namely, the fw_cfg (sub)string in question is [0x46, 0x00, 0xcb, 0x32]. The device is big endian, and the register accessor function should return the 0x4600cb32 host value in qemu. The guest CPU should see the same byte array [0x46, 0x00, 0xcb, 0x32], whose direct interpretation in the little endian guest is 0x32cb0046. ... I think this is a good test case for what we *think* should happen :) I think the following will happen if Peter executes this test: - With the current code, QEMU will print different values when the host endianness changes. - With the patch under discussion, QEMU will print 0x0000000032cb0046 on both host endiannesses. Thanks Laszlo
