Messages in this thread | | | Date | Mon, 20 Jul 2020 16:59:43 -0300 | From | Jason Gunthorpe <> | Subject | Re: [PATCH v2 2/5] mm/migrate: add a direction parameter to migrate_vma |
| |
On Mon, Jul 20, 2020 at 12:54:53PM -0700, Ralph Campbell wrote: > > > diff --git a/include/linux/migrate.h b/include/linux/migrate.h > > > index 3e546cbf03dd..620f2235d7d4 100644 > > > +++ b/include/linux/migrate.h > > > @@ -180,6 +180,11 @@ static inline unsigned long migrate_pfn(unsigned long pfn) > > > return (pfn << MIGRATE_PFN_SHIFT) | MIGRATE_PFN_VALID; > > > } > > > +enum migrate_vma_direction { > > > + MIGRATE_VMA_FROM_SYSTEM, > > > + MIGRATE_VMA_FROM_DEVICE_PRIVATE, > > > +}; > > > > I would have guessed this is more natural as _FROM_DEVICE_ and > > TO_DEVICE_ ? > > The caller controls where the destination memory is allocated so it isn't > necessarily device private memory, it could be from system to system. > The use case for system to system memory migration is for hardware > like ARM SMMU or PCIe ATS where a single set of page tables is shared by > the device and a CPU process over a coherent system memory bus. > Also many integrated GPUs in SOCs fall into this category too.
Maybe just TO/FROM_DEIVCE then? Even though the memory is not DEVICE_PRIVATE it is still device owned pages right?
> So to me, it makes more sense to specify the direction based on the > source location.
It feels strange because the driver doesn't always know or control the source?
Jason
| |