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charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Sat, Dec 14, 2024 at 07:05:15PM +0100, Marek Marczykowski-Górecki wrote: > On Thu, Dec 05, 2024 at 08:41:30PM -0800, Denis Mukhin via B4 Relay wrote: > > The patch series introduces initial in-hypervisor emulator for > > NS8250/NS16x50-compatible UARTs under CONFIG_HAS_VUART_NS8250. > > > > In parallel domain creation scenario (hyperlaunch), NS8520 emulator helps > > early guest OS bringup debugging, because it eliminates dependency on the > > external emulator being operational by the time domains are created. Also, > > there's no early console facility similar to vpl011 to support x86 guest OS > > bring up. > > > > The NS8250 emulator is disabled by default. > > On a high level, why the mechanism used by earlyprintk=xen (IIUC i/o > port 0xe9) isn't enough? > Hyperlaunch can't start full (Xen-unaware) HVM domains anyway, so > a requirement to use a Xen-specific interface for the console shouldn't be > an issue, no? I assume the point is to provide a minimal set of non-Xen specific interfaces so that a guest *could* work if made to use only those interfaces. The 0xE9 hack is quite common for emergency printing, but it doesn't allow for input, which the ns8250 does. Thanks, Roger.