Not the whole page, which may contain other registers too. The XHCI
specification describes DbC as designed to be controlled by a different
driver, but does not mandate placing registers on a separate page. In fact
on Tiger Lake and newer (at least), this page do contain other registers
that Linux tries to use. And with share=yes, a domU would use them too.
Without this patch, PV dom0 would fail to initialize the controller,
while HVM would be killed on EPT violation.
With `share=yes`, this patch gives domU more access to the emulator
(although a HVM with any emulated device already has plenty of it). This
configuration is already documented as unsafe with untrusted guests and
not security supported.
Signed-off-by: Marek Marczykowski-Górecki <marma...@invisiblethingslab.com>
---
Changes in v4:
- restore mmio_ro_ranges in the fallback case
- set XHCI_SHARE_NONE in the fallback case
Changes in v3:
- indentation fix
- remove stale comment
- fallback to pci_ro_device() if subpage_mmio_ro_add() fails
- extend commit message
Changes in v2:
- adjust for simplified subpage_mmio_ro_add() API
---
xen/drivers/char/xhci-dbc.c | 36 ++++++++++++++++++++++--------------
1 file changed, 22 insertions(+), 14 deletions(-)
diff --git a/xen/drivers/char/xhci-dbc.c b/xen/drivers/char/xhci-dbc.c
index 8e2037f1a5f7..c45e4b6825cc 100644
--- a/xen/drivers/char/xhci-dbc.c
+++ b/xen/drivers/char/xhci-dbc.c
@@ -1216,20 +1216,28 @@ static void __init cf_check
dbc_uart_init_postirq(struct serial_port *port)
break;
}
#ifdef CONFIG_X86
- /*
- * This marks the whole page as R/O, which may include other registers
- * unrelated to DbC. Xen needs only DbC area protected, but it seems
- * Linux's XHCI driver (as of 5.18) works without writting to the whole
- * page, so keep it simple.
- */
- if ( rangeset_add_range(mmio_ro_ranges,
- PFN_DOWN((uart->dbc.bar_val & PCI_BASE_ADDRESS_MEM_MASK) +
- uart->dbc.xhc_dbc_offset),
- PFN_UP((uart->dbc.bar_val & PCI_BASE_ADDRESS_MEM_MASK) +
- uart->dbc.xhc_dbc_offset +
- sizeof(*uart->dbc.dbc_reg)) - 1) )
- printk(XENLOG_INFO
- "Error while adding MMIO range of device to mmio_ro_ranges\n");
+ if ( subpage_mmio_ro_add(
+ (uart->dbc.bar_val & PCI_BASE_ADDRESS_MEM_MASK) +
+ uart->dbc.xhc_dbc_offset,
+ sizeof(*uart->dbc.dbc_reg)) )
+ {
+ printk(XENLOG_WARNING
+ "Error while marking MMIO range of XHCI console as R/O, "
+ "making the whole device R/O (share=no)\n");
+ uart->dbc.share = XHCI_SHARE_NONE;
+ if ( pci_ro_device(0, uart->dbc.sbdf.bus, uart->dbc.sbdf.devfn) )
+ printk(XENLOG_WARNING
+ "Failed to mark read-only %pp used for XHCI console\n",
+ &uart->dbc.sbdf);
+ if ( rangeset_add_range(mmio_ro_ranges,
+ PFN_DOWN((uart->dbc.bar_val & PCI_BASE_ADDRESS_MEM_MASK) +
+ uart->dbc.xhc_dbc_offset),
+ PFN_UP((uart->dbc.bar_val & PCI_BASE_ADDRESS_MEM_MASK) +
+ uart->dbc.xhc_dbc_offset +
+ sizeof(*uart->dbc.dbc_reg)) - 1) )
+ printk(XENLOG_INFO
+ "Error while adding MMIO range of device to
mmio_ro_ranges\n");
+ }
#endif
}
--
git-series 0.9.1
