Re: [kvm-unit-tests PATCH v2 14/16] arm/run: Allow Migration tests

[Andrew Jones <drjones@redhat.com>]

On Fri, Jan 10, 2020 at 03:54:10PM +0100, 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>
> Reviewed-by: Thomas Huth <thuth@redhat.com>
> ---
>  arm/Makefile.common |  2 +-
>  arm/run             |  2 +-
>  lib/arm/io.c        | 13 +++++++++++++
>  3 files changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/arm/Makefile.common b/arm/Makefile.common
> index 7cc0f04..327f112 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..ed89e19 100644
> --- a/lib/arm/io.c
> +++ b/lib/arm/io.c
> @@ -87,6 +87,19 @@ void puts(const char *s)
>  	spin_unlock(&uart_lock);
>  }
>  
> +/*
> + * Minimalist implementation for migration completion detection.
> + * Needs to be improved for more advanced Rx cases

Please add that QEMU supports reading a maximum of 16 characters in
this minimal mode. We could even add a counter and then assert if
we try to read 16 or more.

> + */
> +int __getchar(void)
> +{
> +	int ret;
> +
> +	ret = readb(uart0_base);
> +	if (!ret)
> +		return -1;
> +	return ret;
> +}

What about taking the lock?

>  
>  /*
>   * Defining halt to take 'code' as an argument guarantees that it will
> -- 
> 2.20.1
> 

What do you think of the __getchar below?

Thanks,
drew


diff --git a/lib/arm/io.c b/lib/arm/io.c
index 99fd31560084..77beb331d6b2 100644
--- a/lib/arm/io.c
+++ b/lib/arm/io.c
@@ -79,6 +79,31 @@ void io_init(void)
 	chr_testdev_init();
 }
 
+static int ____getchar(void)
+{
+	int c;
+
+	spin_lock(&uart_lock);
+	c = readb(uart0_base);
+	spin_unlock(&uart_lock);
+
+	return c ?: -1;
+}
+
+int __getchar(void)
+{
+	static int count;
+	int c;
+
+	if ((c = ____getchar()) != -1)
+		++count;
+
+	/* Without special UART initialization we can only read 16 characters. */
+	assert(count < 16);
+
+	return c;
+}
+
 void puts(const char *s)
 {
 	spin_lock(&uart_lock);