Message ID | 20171107034301.35120-1-aik@ozlabs.ru (mailing list archive) |
---|---|
State | Accepted |
Commit | 9003a249815a15704f415954039d1c7ea27da9ad |
Headers | show |
Series | [kernel,v2] powerpc/powernv/ioda: Remove explicit max window size check | expand |
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 */
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
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 */
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(-)