Re: [kvm-unit-tests PATCH v3 12/14] arm/run: Allow Migration tests

[Auger Eric]

Hi Thomas,

On 1/29/20 9:07 AM, Thomas Huth wrote:
> On 28/01/2020 11.34, Eric Auger wrote:
>> Let's link getchar.o to use puts and getchar from the
>> tests.
>>
>> Then allow tests belonging to the migration group to
>> trigger the migration from the test code by putting
>> "migrate" into the uart. Then the code can wait for the
>> migration completion by using getchar().
>>
>> The __getchar implement is minimalist as it just reads the
>> data register. It is just meant to read the single character
>> emitted at the end of the migration by the runner script.
>>
>> It is not meant to read more data (FIFOs are not enabled).
>>
>> Signed-off-by: Eric Auger <address@hidden>
>>
>> ---
>>
>> v2 -> v3:
>> - take the lock
>> - assert if more than 16 chars
>> - removed Thomas' R-b
>> ---
>>  arm/Makefile.common |  2 +-
>>  arm/run             |  2 +-
>>  lib/arm/io.c        | 28 ++++++++++++++++++++++++++++
>>  3 files changed, 30 insertions(+), 2 deletions(-)
>>
>> diff --git a/arm/Makefile.common b/arm/Makefile.common
>> index b8988f2..a123e85 100644
>> --- a/arm/Makefile.common
>> +++ b/arm/Makefile.common
>> @@ -32,7 +32,7 @@ CFLAGS += -I $(SRCDIR)/lib -I $(SRCDIR)/lib/libfdt -I lib
>>  asm-offsets = lib/$(ARCH)/asm-offsets.h
>>  include $(SRCDIR)/scripts/asm-offsets.mak
>>  
>> -cflatobjs += lib/util.o
>> +cflatobjs += lib/util.o lib/getchar.o
>>  cflatobjs += lib/alloc_phys.o
>>  cflatobjs += lib/alloc_page.o
>>  cflatobjs += lib/vmalloc.o
>> diff --git a/arm/run b/arm/run
>> index 277db9b..a390ca5 100755
>> --- a/arm/run
>> +++ b/arm/run
>> @@ -61,6 +61,6 @@ fi
>>  M+=",accel=$ACCEL"
>>  command="$qemu -nodefaults $M -cpu $processor $chr_testdev $pci_testdev"
>>  command+=" -display none -serial stdio -kernel"
>> -command="$(timeout_cmd) $command"
>> +command="$(migration_cmd) $(timeout_cmd) $command"
>>  
>>  run_qemu $command "$@"
>> diff --git a/lib/arm/io.c b/lib/arm/io.c
>> index 99fd315..d8e7745 100644
>> --- a/lib/arm/io.c
>> +++ b/lib/arm/io.c
>> @@ -87,6 +87,34 @@ void puts(const char *s)
>>      spin_unlock(&uart_lock);
>>  }
>>  
>> +static int ____getchar(void)
> 
> Three underscores? ... that's quite a lot already. I'd maybe rather name
> the function "do_getchar" or something similar instead. Or simply merge
> the code into the __getchar function below - it's just three lines.
OK
> 
>> +{
>> +    int c;
>> +
>> +    spin_lock(&uart_lock);
>> +    c = readb(uart0_base);
>> +    spin_unlock(&uart_lock);
>> +
>> +    return c ? : -1;
> 
> Just a matter of taste, but I prefer the elvis operator without space in
> between.
OK
> 
>> +}
>> +
>> +/*
>> + * Minimalist implementation for migration completion detection.
>> + * Without FIFOs enabled on the QEMU UART device we just read
>> + * the data register: we cannot read more than 16 characters.
> 
> Where are the 16 bytes buffered if FIFOs are disabled?
I think this is in the PL011 data register (UARTDR), 4 words.
https://developer.arm.com/docs/ddi0183/latest/programmers-model/register-descriptions/data-register-uartdr

> 
>> + */
>> +int __getchar(void)
>> +{
>> +    int c = ____getchar();
>> +    static int count;
>> +
>> +    if (c != -1)
>> +            ++count;
>> +
>> +    assert(count < 16);
>> +
>> +    return c;
>> +}
> 
> The above comments were only nits ... feel free to ignore them if you
> don't want to respin the series just because of this.
No Problem. Thank you for your time.

Thanks

Eric
> 
>  Thomas
>