Re: [PATCH v2 0/4] apic: Fix migration breakage of >255 vcpus

[John Snow]

On 10/23/19 4:17 AM, Kevin Wolf wrote:
> The important difference here is legacy IDE (which works) vs. AHCI
> (which doesn't work). If you add a -device ahci to the -M pc case, it
> starts failing, too.
> 
> Not sure why AHCI fails, but I'll just CC John who is the lucky
> maintainer of this device. :-)

Hm... It looks like SeaBIOS is identifying the drive correctly and
perfectly well, but we're failing at boot_disk(u8 bootdrv, int
checksig), about here:

call16_int(0x13, &br);

if (br.flags & F_CF) {
    printf("Boot failed: could not read the boot disk\n\n");
    return;
}

Looking at AHCI tracing (From the QEMU side), it looks like we set up
the drive correctly, and then never touch the port ever again -- I don't
see an attempted read on QEMU's end.

I'll need to look through SeaBIOS source for hints, I'm not sure right
yet. If anyone is more familiar with the SeaBIOS boot code, maybe they
can give a pointer faster than I'll figure it out myself.

--js