On 6/28/23 6:39 AM, Ritesh Harjani (IBM) wrote:

"Aneesh Kumar K.V" [off-list ref] writes:

quoted

Arm disabled hugetlb vmemmap optimization [1] because hugetlb vmemmap
optimization includes an update of both the permissions (writeable to
read-only) and the output address (pfn) of the vmemmap ptes. That is not
supported without unmapping of pte(marking it invalid) by some
architectures.

With DAX vmemmap optimization we don't require such pte updates and
architectures can enable DAX vmemmap optimization while having hugetlb
vmemmap optimization disabled. Hence split DAX optimization support into a
different config.

loongarch and riscv don't have devdax support. So the DAX config is not
enabled for them. With this change, arm64 should be able to select DAX
optimization

[1] commit 060a2c92d1b6 ("arm64: mm: hugetlb: Disable HUGETLB_PAGE_OPTIMIZE_VMEMMAP")

Signed-off-by: Aneesh Kumar K.V <redacted>
---
 arch/loongarch/Kconfig | 2 +-
 arch/riscv/Kconfig     | 2 +-
 arch/x86/Kconfig       | 3 ++-
 fs/Kconfig             | 2 +-
 include/linux/mm.h     | 2 +-
 mm/Kconfig             | 5 ++++-
 6 files changed, 10 insertions(+), 6 deletions(-)

what about s390?

git grep "ARCH_WANT_OPTIMIZE_VMEMMAP" .
arch/s390/Kconfig:      select ARCH_WANT_OPTIMIZE_VMEMMAP

Thanks for catching that. Updated

-aneesh