ns16550: MMIO r/o ranges are maintained at page granularity

Passing byte granular values will not have the intended effect. Address
the immediate issue, but I don't think what we do is actually
sufficient: At least some devices allow access to their registers via
either I/O ports or MMIO. In such aliasing cases we'd need to protect
the MMIO range even when we use I/O port accesses to drive the port.

Note that this way we may write-protect MMIO ranges of unrelated devices
as well. To deal with this, faults resulting from this would need
handling, to emulate the accesses outside of the protected range. (An
alternative would be to relocate the BAR, but I'm afraid this might end
up even more challenging.)

Fixes: c9f8e0aee507 ("ns16550: Add support for UART present in Broadcom TruManage capable NetXtreme chips")
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>

diff --git a/xen/drivers/char/ns16550.c b/xen/drivers/char/ns16550.c
index e2c24082c368110cce5f93c43a81cdd096fbf7cf..30596d60d4ed3adc34d9d50f3ea481dfd3c62a33 100644 (file)
--- a/xen/drivers/char/ns16550.c
+++ b/xen/drivers/char/ns16550.c
@@ -421,8 +421,8 @@ static void __init ns16550_init_postirq(struct serial_port *port)
     if ( uart->bar || uart->ps_bdf_enable )
     {
         if ( uart->param && uart->param->mmio &&
-             rangeset_add_range(mmio_ro_ranges, uart->io_base,
-                                uart->io_base + uart->io_size - 1) )
+             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],