On Mon, Nov 20, 2023 at 03:10:06PM +0000, Andrew Cooper wrote:
> The MP spec requires a minimum of 1k alignment. So too does Xen's use of a
> single fixmap page to map the IO-APIC.
>
> Reject out-of-spec values so we don't end up in a position where a bad
> firmware value causes Xen to use the wrong mapping.
>
> Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com>
> ---
> CC: Jan Beulich <jbeul...@suse.com>
> CC: Wei Liu <w...@xen.org>
> CC: Roger Pau Monné <roger....@citrix.com>
> ---
> xen/arch/x86/io_apic.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/xen/arch/x86/io_apic.c b/xen/arch/x86/io_apic.c
> index 0ef61fb2f167..db1ea6e2f2ca 100644
> --- a/xen/arch/x86/io_apic.c
> +++ b/xen/arch/x86/io_apic.c
> @@ -2589,10 +2589,11 @@ static void __init ioapic_init_mappings(void)
> union IO_APIC_reg_01 reg_01;
> paddr_t ioapic_phys = mp_ioapics[i].mpc_apicaddr;
>
> - if ( !ioapic_phys )
> + if ( !ioapic_phys || (ioapic_phys & (KB(1) - 1)) )
Might be clearer to use !IS_ALIGNED(), otherwise:
Reviewed-by: Roger Pau Monné <roger....@citrix.com>
> {
> printk(KERN_ERR
> - "WARNING: bogus zero IO-APIC address found in MPTABLE,
> disabling IO/APIC support!\n");
> + "WARNING: bogus IO-APIC address %08lx found in MPTABLE,
> disabling IO/APIC support!\n",
FWIW, I think the '!' at the end is not useful, and I would adjust
the last 'IO/APIC' to 'IO-APIC' if already modifying the line.
Thanks, Roger.
