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

[Thomas Huth <thuth@redhat.com>]

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 <eric.auger@redhat.com>
> 
> ---
> 
> 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.

> +{
> +	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.

> +}
> +
> +/*
> + * 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?

> + */
> +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.

 Thomas