On Fri, 17 Oct 2025, 18:16 Andrew Cooper, <[email protected]> wrote:
> Hi, > > I think we've got a bug with the serial console. I'm reliably loosing a > small part of the boot message. e.g.: > > (XEN) Latest ChangeSet: Fri Oct 17 17:24:59 2025 git:5e79cfcd2100 > (XEN) build-id: d1536ff6698b3e3ba307d551abf > Family 25 (0x19 Stepping 1 (raw 00a00f11) > (XEN) BSP microcode revision: 0x0a001137 > > whereas from xl dmesg after the system boots, we see things correctly: > > (XEN) Latest ChangeSet: Fri Oct 17 17:24:59 2025 git:5e79cfcd2100 > (XEN) build-id: d1536ff6698b3b8968e883fc39e3ba307d551abf > (XEN) CPU Vendor: AMD, Family 25 (0x19), Model 1 (0x1), Stepping 1 (raw > 00a00f11) > (XEN) BSP microcode revision: 0x0a001137 > > > The lost bit of text differs even when rebooting the same Xen binary, > but it's always around this area, very early on boot. > > I've been seeing this for a little while, but one of my common dev > machines is showing it fairly reliably at the moment. > > Checking a transcript of the terminal, we're missing characters, rather > than having additional control characters causing the corruption. > > I suppose I need to stare at console_init_preirq() some more, but if > anyone has ideas, I'm all ears. > > ~Andrew > Hi, I would guess the code for early boot is different and is not waiting correctly if the serial is able to accept new characters so the hardware buffer is overwritten. Frediano >
