PVH Dom0 related UART failure

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

Hi all,

I have run into another PVH Dom0 issue. I am trying to enable a PVH Dom0
test with the brand new gitlab-ci runner offered by Qubes. It is an AMD
Zen3 system and we already have a few successful tests with it, see
automation/gitlab-ci/test.yaml.

We managed to narrow down the issue to a console problem. We are
currently using console=com1 com1=115200,8n1,pci,msi as Xen command line
options, it works with PV Dom0 and it is using a PCI UART card.

In the case of Dom0 PVH:
- it works without console=com1
- it works with console=com1 and with the patch appended below
- it doesn't work otherwise and crashes with this error:
https://matrix-client.matrix.org/_matrix/media/r0/download/invisiblethingslab.com/uzcmldIqHptFZuxqsJtviLZK

What is the right way to fix it?

Keep in mind that I don't have access to the system except via gitlab-ci
pipelines. Marek (CCed) might have more info on the system and the PCI
UART he is using in case it's needed.

Many thanks for any help you can provide.

Cheers,

Stefano


diff --git a/xen/drivers/char/ns16550.c b/xen/drivers/char/ns16550.c
index 212a9c49ae..57623bc091 100644
--- a/xen/drivers/char/ns16550.c
+++ b/xen/drivers/char/ns16550.c
@@ -429,17 +428,6 @@ static void __init cf_check ns16550_init_postirq(struct 
serial_port *port)
 #ifdef NS16550_PCI
     if ( uart->bar || uart->ps_bdf_enable )
     {
-        if ( uart->param && uart->param->mmio &&
-             rangeset_add_range(mmio_ro_ranges, PFN_DOWN(uart->io_base),
-                                PFN_UP(uart->io_base + uart->io_size) - 1) )
-            printk(XENLOG_INFO "Error while adding MMIO range of device to 
mmio_ro_ranges\n");
-
-        if ( pci_ro_device(0, uart->ps_bdf[0],
-                           PCI_DEVFN(uart->ps_bdf[1], uart->ps_bdf[2])) )
-            printk(XENLOG_INFO "Could not mark config space of %02x:%02x.%u 
read-only.\n",
-                   uart->ps_bdf[0], uart->ps_bdf[1],
-                   uart->ps_bdf[2]);
-
         if ( uart->msi )
         {
             struct msi_info msi = {