Re: [Qemu-devel] [PATCH 15/15] qtest: add rtc-test test-case

[Paolo Bonzini]

On 01/10/2012 08:10 PM, Anthony Liguori wrote:
> +    sec = cmos_read(0x00);
> +    min = cmos_read(0x02);
> +    hour = cmos_read(0x04);
> +    mday = cmos_read(0x07);
> +    mon = cmos_read(0x08);
> +    year = cmos_read(0x09);

Please use identifiers for register numbers.

> +    /*
> +     * This check assumes a few things.  First, we cannot guarantee that we get
> +     * a consistent reading from the wall clock because we may hit an edge of
> +     * the clock while reading.  To work around this, we read four clock 
> readings
> +     * such that at least two of them should match.  We need to assume that one
> +     * reading is corrupt so we need four readings to ensure that we have at
> +     * least two consecutive identical readings
> +     *
> +     * It's also possible that we'll cross an edge reading the host clock so
> +     * simply check to make sure that the clock reading is within the period of
> +     * when we expect it to be.
> +     */

This seems broken to me.  The right thing to do would be to run the test 
with vm_clock for the rtc_clock, add a way for the qtest machine to bump 
the vm_clock to the next event, and busy loop running that method using 
UIP like you would do on hardware.

Paolo