[Qemu-devel] [PATCH qemu] vfio, spapr: Fix levels calculation

[Qemu-devel] [PATCH qemu] vfio, spapr: Fix levels calculation

[Alexey Kardashevskiy]

The existing tries to round up the number of pages but @pages is always
calculated as the rounded up value minus one  which makes ctz64() always
return 0 and have create.levels always set 1.

This removes wrong "-1" and allows having more than 1 levels. This becomes
handy for >128GB guests with standard 64K pages as this requires blocks
with zone order 9 and the popular limit of CONFIG_FORCE_MAX_ZONEORDER=9
means that only blocks up to order 8 are allowed.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
 hw/vfio/spapr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/vfio/spapr.c b/hw/vfio/spapr.c
index 32fd6a9b54..259397c002 100644
--- a/hw/vfio/spapr.c
+++ b/hw/vfio/spapr.c
@@ -163,7 +163,7 @@ int vfio_spapr_create_window(VFIOContainer *container,
      */
     entries = create.window_size >> create.page_shift;
     pages = MAX((entries * sizeof(uint64_t)) / getpagesize(), 1);
-    pages = MAX(pow2ceil(pages) - 1, 1); /* Round up */
+    pages = MAX(pow2ceil(pages), 1); /* Round up */
     create.levels = ctz64(pages) / 6 + 1;
 
     ret = ioctl(container->fd, VFIO_IOMMU_SPAPR_TCE_CREATE, &create);
-- 
2.11.0

Re: [Qemu-devel] [PATCH qemu] vfio, spapr: Fix levels calculation

[David Gibson]

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On Tue, Sep 12, 2017 at 12:53:07PM +1000, Alexey Kardashevskiy wrote:
> The existing tries to round up the number of pages but @pages is always
> calculated as the rounded up value minus one  which makes ctz64() always
> return 0 and have create.levels always set 1.
> 
> This removes wrong "-1" and allows having more than 1 levels. This becomes
> handy for >128GB guests with standard 64K pages as this requires blocks
> with zone order 9 and the popular limit of CONFIG_FORCE_MAX_ZONEORDER=9
> means that only blocks up to order 8 are allowed.
> 
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>

Applied to ppc-for-2.11.

> ---
>  hw/vfio/spapr.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/hw/vfio/spapr.c b/hw/vfio/spapr.c
> index 32fd6a9b54..259397c002 100644
> --- a/hw/vfio/spapr.c
> +++ b/hw/vfio/spapr.c
> @@ -163,7 +163,7 @@ int vfio_spapr_create_window(VFIOContainer *container,
>       */
>      entries = create.window_size >> create.page_shift;
>      pages = MAX((entries * sizeof(uint64_t)) / getpagesize(), 1);
> -    pages = MAX(pow2ceil(pages) - 1, 1); /* Round up */
> +    pages = MAX(pow2ceil(pages), 1); /* Round up */
>      create.levels = ctz64(pages) / 6 + 1;
>  
>      ret = ioctl(container->fd, VFIO_IOMMU_SPAPR_TCE_CREATE, &create);

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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