Re: [Qemu-devel] [PATCH] qtest: ask endianness of the target in qtest_init()

[Laurent Vivier]

On 06/10/2016 22:45, Peter Maydell wrote:
> On 6 October 2016 at 11:56, Laurent Vivier <address@hidden> wrote:
>> The target endianness is not deduced anymore from
>> the architecture name but asked directly to the guest,
>> using a new qtest command: "endianness". As it can't
>> change (this is the value of TARGET_WORDS_BIGENDIAN),
>> we store it to not have to ask every time we want to
>> know if we have to byte-swap a value.
>>
>> Signed-off-by: Laurent Vivier <address@hidden>
>> CC: Greg Kurz <address@hidden>
>> CC: David Gibson <address@hidden>
>> CC: Peter Maydell <address@hidden>
>> ---
>> Note: this patch can be seen as a v2 of
>> "qtest: evaluate endianness of the target in qtest_init()"
>> from the patch series "tests: enable virtio tests on SPAPR"
>> in which I have added the idea from Peter to ask the endianness
>> directly to the guest using a new qtest command.
>>
>>  qtest.c                   |   7 ++
>>  tests/libqos/virtio-pci.c |   2 +-
>>  tests/libqtest.c          | 224 
>> ++++++++++++++++++++--------------------------
>>  tests/libqtest.h          |  16 +++-
>>  tests/virtio-blk-test.c   |   2 +-
>>  5 files changed, 118 insertions(+), 133 deletions(-)
>>
>> diff --git a/qtest.c b/qtest.c
>> index 22482cc..b53b39c 100644
>> --- a/qtest.c
>> +++ b/qtest.c
>> @@ -537,6 +537,13 @@ static void qtest_process_command(CharDriverState *chr, 
>> gchar **words)
>>
>>          qtest_send_prefix(chr);
>>          qtest_send(chr, "OK\n");
>> +    } else if (strcmp(words[0], "endianness") == 0) {
>> +        qtest_send_prefix(chr);
>> +#if defined(TARGET_WORDS_BIGENDIAN)
>> +        qtest_sendf(chr, "OK big\n");
>> +#else
>> +        qtest_sendf(chr, "OK little\n");
>> +#endif
>>  #ifdef TARGET_PPC64
>>      } else if (strcmp(words[0], "rtas") == 0) {
>>          uint64_t res, args, ret;
>> diff --git a/tests/libqos/virtio-pci.c b/tests/libqos/virtio-pci.c
>> index 18b92b9..6e005c1 100644
>> --- a/tests/libqos/virtio-pci.c
>> +++ b/tests/libqos/virtio-pci.c
>> @@ -86,7 +86,7 @@ static uint64_t qvirtio_pci_config_readq(QVirtioDevice *d, 
>> uint64_t addr)
>>      int i;
>>      uint64_t u64 = 0;
>>
>> -    if (qtest_big_endian()) {
>> +    if (target_big_endian()) {
>>          for (i = 0; i < 8; ++i) {
>>              u64 |= (uint64_t)qpci_io_readb(dev->pdev,
>>                                  (void *)(uintptr_t)addr + i) << (7 - i) * 8;
> 
> Why rename the function? We're only changing its
> implementation.

Because in libqtest.c, qtest_XXXX() functions take always a QTestState
argument, and then in libqtest.h, we have an inline like "inline static
XXXX(...) { qtest_XXXX(global_qtest ...) }".

>> diff --git a/tests/libqtest.c b/tests/libqtest.c
>> index 6f6bdf1..27cf6b1 100644
>> --- a/tests/libqtest.c
>> +++ b/tests/libqtest.c
>> @@ -37,6 +37,7 @@ struct QTestState
>>      bool irq_level[MAX_IRQ];
>>      GString *rx;
>>      pid_t qemu_pid;  /* our child QEMU process */
>> +    bool big_endian;
>>  };
>>
>>  static GHookList abrt_hooks;
>> @@ -146,89 +147,6 @@ void qtest_add_abrt_handler(GHookFunc fn, const void 
>> *data)
>>      g_hook_prepend(&abrt_hooks, hook);
>>  }
>>
>> -QTestState *qtest_init(const char *extra_args)
>> -{
>> -    QTestState *s;
>> -    int sock, qmpsock, i;
>> -    gchar *socket_path;
>> -    gchar *qmp_socket_path;
>> -    gchar *command;
>> -    const char *qemu_binary;
>> -
>> -    qemu_binary = getenv("QTEST_QEMU_BINARY");
>> -    g_assert(qemu_binary != NULL);
> 
> This diff arrangement makes the patch a bit hard to read;
> what meant that the functions had to be moved around?

Yes, I know. I move this function after qtest_sendf() and qtest_rsp() to
not have to declare them before. There are no circular dependencies, so
we can.

> 
>> +    /* ask endianness of the target */
>> +
>> +    qtest_sendf(s, "endianness\n");
>> +    args = qtest_rsp(s, 1);
>> +    g_assert(strcmp(args[1], "big") == 0 || strcmp(args[1], "little") == 0);
>> +    s->big_endian = strcmp(args[1], "big") == 0;
>> +    g_strfreev(args);
> 
> This would be better in its own utility function, I think.

Yes, I agree, but my wondering was how to name it :P ,
qtest_big_endian() and target_big_endian() are already in use, and as it
is a 6 lines function, used once, I guessed we could inline it here.

Thanks,
Laurent