* [PATCH kernel v2] powerpc/powernv/ioda: Remove explicit max window size check
@ 2017-11-07 3:43 Alexey Kardashevskiy
2017-11-13 23:52 ` David Gibson
2017-11-14 11:12 ` [kernel, " Michael Ellerman
0 siblings, 2 replies; 3+ messages in thread
From: Alexey Kardashevskiy @ 2017-11-07 3:43 UTC (permalink / raw)
To: linuxppc-dev
Cc: Alexey Kardashevskiy, David Gibson, Russell Currey, Jonas Pfefferle1
DMA windows can only have a size of power of two on IODA2 hardware and
using memory_hotplug_max() to determine the upper limit won't work
correcly if it returns not power of two value.
This removes the check as the platform code does this check in
pnv_pci_ioda2_setup_default_config() anyway; the other client is VFIO
and that thing checks against locked_vm limit which prevents the userspace
from locking too much memory.
It is expected to impact DPDK on machines with non-power-of-two RAM size,
mostly. KVM guests are less likely to be affected as usually guests get
less than half of hosts RAM.
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
Changes:
v2:
* instead of relaxing the check, this simply removes it
---
arch/powerpc/platforms/powernv/pci-ioda.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
index 1de94fb..433cf84 100644
--- a/arch/powerpc/platforms/powernv/pci-ioda.c
+++ b/arch/powerpc/platforms/powernv/pci-ioda.c
@@ -2776,7 +2776,7 @@ static long pnv_pci_ioda2_table_alloc_pages(int nid, __u64 bus_offset,
if (!levels || (levels > POWERNV_IOMMU_MAX_LEVELS))
return -EINVAL;
- if ((window_size > memory_hotplug_max()) || !is_power_of_2(window_size))
+ if (!is_power_of_2(window_size))
return -EINVAL;
/* Adjust direct table size from window_size and levels */
--
2.11.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH kernel v2] powerpc/powernv/ioda: Remove explicit max window size check
2017-11-07 3:43 [PATCH kernel v2] powerpc/powernv/ioda: Remove explicit max window size check Alexey Kardashevskiy
@ 2017-11-13 23:52 ` David Gibson
2017-11-14 11:12 ` [kernel, " Michael Ellerman
1 sibling, 0 replies; 3+ messages in thread
From: David Gibson @ 2017-11-13 23:52 UTC (permalink / raw)
To: Alexey Kardashevskiy; +Cc: linuxppc-dev, Russell Currey, Jonas Pfefferle1
[-- Attachment #1: Type: text/plain, Size: 2037 bytes --]
On Tue, Nov 07, 2017 at 02:43:01PM +1100, Alexey Kardashevskiy wrote:
> DMA windows can only have a size of power of two on IODA2 hardware and
> using memory_hotplug_max() to determine the upper limit won't work
> correcly if it returns not power of two value.
>
> This removes the check as the platform code does this check in
> pnv_pci_ioda2_setup_default_config() anyway; the other client is VFIO
> and that thing checks against locked_vm limit which prevents the userspace
> from locking too much memory.
>
> It is expected to impact DPDK on machines with non-power-of-two RAM size,
> mostly. KVM guests are less likely to be affected as usually guests get
> less than half of hosts RAM.
>
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
This _can_ be called with essentially arbitrary window_size via the
VFIO code. However, that should be constrained by the locked memory
limit, which is checked before this gets called.
> ---
> Changes:
> v2:
> * instead of relaxing the check, this simply removes it
> ---
> arch/powerpc/platforms/powernv/pci-ioda.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
> index 1de94fb..433cf84 100644
> --- a/arch/powerpc/platforms/powernv/pci-ioda.c
> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
> @@ -2776,7 +2776,7 @@ static long pnv_pci_ioda2_table_alloc_pages(int nid, __u64 bus_offset,
> if (!levels || (levels > POWERNV_IOMMU_MAX_LEVELS))
> return -EINVAL;
>
> - if ((window_size > memory_hotplug_max()) || !is_power_of_2(window_size))
> + if (!is_power_of_2(window_size))
> return -EINVAL;
>
> /* Adjust direct table size from window_size and levels */
--
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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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [kernel, v2] powerpc/powernv/ioda: Remove explicit max window size check
2017-11-07 3:43 [PATCH kernel v2] powerpc/powernv/ioda: Remove explicit max window size check Alexey Kardashevskiy
2017-11-13 23:52 ` David Gibson
@ 2017-11-14 11:12 ` Michael Ellerman
1 sibling, 0 replies; 3+ messages in thread
From: Michael Ellerman @ 2017-11-14 11:12 UTC (permalink / raw)
To: Alexey Kardashevskiy, linuxppc-dev
Cc: Alexey Kardashevskiy, Jonas Pfefferle1, David Gibson
On Tue, 2017-11-07 at 03:43:01 UTC, Alexey Kardashevskiy wrote:
> DMA windows can only have a size of power of two on IODA2 hardware and
> using memory_hotplug_max() to determine the upper limit won't work
> correcly if it returns not power of two value.
>
> This removes the check as the platform code does this check in
> pnv_pci_ioda2_setup_default_config() anyway; the other client is VFIO
> and that thing checks against locked_vm limit which prevents the userspace
> from locking too much memory.
>
> It is expected to impact DPDK on machines with non-power-of-two RAM size,
> mostly. KVM guests are less likely to be affected as usually guests get
> less than half of hosts RAM.
>
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Applied to powerpc next, thanks.
https://git.kernel.org/powerpc/c/9003a249815a15704f415954039d1c
cheers
^ permalink raw reply [flat|nested] 3+ messages in thread
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2017-11-13 23:52 ` David Gibson
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