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Re: [PATCH 1/2] ns16550: reject IRQ above nr_irqs



Hi,

On 10/03/2022 16:12, Roger Pau Monné wrote:
On Thu, Mar 10, 2022 at 05:08:07PM +0100, Jan Beulich wrote:
On 10.03.2022 16:47, Roger Pau Monné wrote:
On Thu, Mar 10, 2022 at 04:23:00PM +0100, Jan Beulich wrote:
On 10.03.2022 15:34, Marek Marczykowski-Górecki wrote:
--- a/xen/drivers/char/ns16550.c
+++ b/xen/drivers/char/ns16550.c
@@ -1221,6 +1221,9 @@ pci_uart_config(struct ns16550 *uart, bool_t skip_amt, 
unsigned int idx)
                              pci_conf_read8(PCI_SBDF(0, b, d, f),
                                             PCI_INTERRUPT_LINE) : 0;
+ if (uart->irq >= nr_irqs)
+                    uart->irq = 0;

Don't you mean nr_irqs_gsi here? Also (nit) please add the missing blanks
immediately inside the parentheses.

If we use nr_irqs_gsi we will need to make the check x86 only AFAICT.

Down the road (when Arm wants to select HAS_PCI) - yes. Not necessarily
right away. After all Arm wants to have an equivalent check here then,
not merely checking against nr_irqs instead. So putting a conditional
here right away would hide the need for putting in place an Arm-specific
alternative.

Oh, I always forget Arm doesn't have CONFIG_HAS_PCI enabled just yet.
The PCI code in ns16550.c is gated by CONFIG_HAS_PCI and CONFIG_X86. I am not sure we will ever see a support for PCI UART card in Xen on Arm.

However, if it evers happens then neither nr_irqs or nr_irqs_gsi would help here because from the interrupt controller PoV 0xff may be a valid (GICv2 supports up to 1024 interrupts).

Is there any reason we can't explicitely check 0xff?

Cheers,

--
Julien Grall



 


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