Re: [Qemu-devel] [PATCH 1/2] qemu kvm: Set up gsi bitmap correctly

[Jan Kiszka]

On 2012-03-27 23:00, Jason Baron wrote:
> The current 'kvm_init_irq_routing()' doesn't set up the gsi bitmap
> correctly, and as a consequence pins max_gsi to 32 when it really
> should be 1024. I ran into this limitation while testing pci
> passthrough, where I consistently would get -ENOSPACE return from
> kvm_get_irq_route_gsi() in assigned_dev_update_msix_mmio().
> 
> Signed-off-by: Jason Baron <address@hidden>
> ---
>  kvm-all.c  |    4 ++--
>  qemu-kvm.c |    2 +-
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/kvm-all.c b/kvm-all.c
> index ab88c7c..7d602af 100644
> --- a/kvm-all.c
> +++ b/kvm-all.c
> @@ -873,9 +873,9 @@ static void kvm_init_irq_routing(KVMState *s)
>          unsigned int gsi_bits, i;
>  
>          /* Round up so we can search ints using ffs */
> -        gsi_bits = (gsi_count + 31) / 32;
> +        gsi_bits = ALIGN(gsi_count, 32);

Oops.

>          s->used_gsi_bitmap = g_malloc0(gsi_bits / 8);
> -        s->max_gsi = gsi_bits;
> +        s->max_gsi = gsi_count;
>  
>          /* Mark any over-allocated bits as already in use */
>          for (i = gsi_count; i < gsi_bits; i++) {

When redefining its semantic anyway, ket's take the chance and rename
gsi_max to gsi_count. gsi_max actually sounds to me like gsi_count - 1.

This change should then be a uq/master patch. The other bits for
qemu-kvm can build on top.

> diff --git a/qemu-kvm.c b/qemu-kvm.c
> index 2047ebb..b17cae0 100644
> --- a/qemu-kvm.c
> +++ b/qemu-kvm.c
> @@ -249,7 +249,7 @@ int kvm_get_irq_route_gsi(void)
>      uint32_t *buf = s->used_gsi_bitmap;
>  
>      /* Return the lowest unused GSI in the bitmap */
> -    for (i = 0; i < s->max_gsi / 32; i++) {
> +    for (i = 0; i < (ALIGN(s->max_gsi, 32) / 32); i++) {
>          bit = ffs(~buf[i]);
>          if (!bit) {
>              continue;

Would be nicer to hold the loop limit in local variable.

Jan

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