svn commit: r332735 - head/sys/x86/x86

[Eric Joyner]

Is the limit going to be increased at some point? Is there a true limit
somewhere?

On Wed, Apr 18, 2018 at 11:45 AM, John Baldwin <jhb at freebsd.org> wrote:

> Author: jhb
> Date: Wed Apr 18 18:45:34 2018
> New Revision: 332735
> URL: https://svnweb.freebsd.org/changeset/base/332735
>
> Log:
>   Fix two off-by-one errors when allocating MSI and MSI-X interrupts.
>
>   x86 enforces an (arbitray) limit on the number of available MSI and
>   MSI-X interrupts to simplify code (in particular, interrupt_source[]
>   is statically sized).  This means that an attempt to allocate an MSI
>   vector needs to fail if it would go beyond the limit, but the checks
>   for exceeding the limit had an off-by-one error.  In the case of MSI-X
>   which allocates interrupts one at a time this meant that IRQ 768 kept
>   getting handed out multiple times for msix_alloc() instead of failing
>   because all MSI IRQs were in use.
>
>   Tested by:    lidl
>   MFC after:    1 week
>
> Modified:
>   head/sys/x86/x86/msi.c
>
> Modified: head/sys/x86/x86/msi.c
> ============================================================
> ==================
> --- head/sys/x86/x86/msi.c      Wed Apr 18 18:45:04 2018        (r332734)
> +++ head/sys/x86/x86/msi.c      Wed Apr 18 18:45:34 2018        (r332735)
> @@ -404,7 +404,7 @@ again:
>         /* Do we need to create some new sources? */
>         if (cnt < count) {
>                 /* If we would exceed the max, give up. */
> -               if (i + (count - cnt) > FIRST_MSI_INT + NUM_MSI_INTS) {
> +               if (i + (count - cnt) >= FIRST_MSI_INT + NUM_MSI_INTS) {
>                         mtx_unlock(&msi_lock);
>                         free(mirqs, M_MSI);
>                         return (ENXIO);
> @@ -645,7 +645,7 @@ again:
>         /* Do we need to create a new source? */
>         if (msi == NULL) {
>                 /* If we would exceed the max, give up. */
> -               if (i + 1 > FIRST_MSI_INT + NUM_MSI_INTS) {
> +               if (i + 1 >= FIRST_MSI_INT + NUM_MSI_INTS) {
>                         mtx_unlock(&msi_lock);
>                         return (ENXIO);
>                 }
>
>