diff mbox series

[39/46] hugetlb: x86: enable high-granularity mapping

Message ID 20230105101844.1893104-40-jthoughton@google.com
State New
Headers
Series Based on latest mm-unstable (85b44c25cd1e). |

Commit Message

James Houghton Jan. 5, 2023, 10:18 a.m. UTC 
  Now that HGM is fully supported for GENERAL_HUGETLB, x86 can enable it.
The x86 KVM MMU already properly handles HugeTLB HGM pages (it does a
page table walk to determine which size to use in the second-stage page
table instead of, for example, checking vma_mmu_pagesize, like arm64
does).

We could also enable HugeTLB HGM for arm (32-bit) at this point, as it
also uses GENERAL_HUGETLB and I don't see anything else that is needed
for it. However, I haven't tested on arm at all, so I won't enable it.

Signed-off-by: James Houghton <jthoughton@google.com>
---
 arch/x86/Kconfig | 1 +
 1 file changed, 1 insertion(+)

Comments

James Houghton Jan. 12, 2023, 8:07 p.m. UTC | #1 
On Thu, Jan 5, 2023 at 5:19 AM James Houghton <jthoughton@google.com> wrote:
>
> Now that HGM is fully supported for GENERAL_HUGETLB, x86 can enable it.
> The x86 KVM MMU already properly handles HugeTLB HGM pages (it does a
> page table walk to determine which size to use in the second-stage page
> table instead of, for example, checking vma_mmu_pagesize, like arm64
> does).
>
> We could also enable HugeTLB HGM for arm (32-bit) at this point, as it
> also uses GENERAL_HUGETLB and I don't see anything else that is needed
> for it. However, I haven't tested on arm at all, so I won't enable it.

Given that we are using a high bit for VM_HUGETLB_HGM, we can only
support 64-bit architectures. Userfaultfd minor faults is limited to
64-bit architectures for the same reason: VM_UFFD_MINOR uses a bit.

>
> Signed-off-by: James Houghton <jthoughton@google.com>
> ---
>  arch/x86/Kconfig | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 3604074a878b..3d08cd45549c 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -126,6 +126,7 @@ config X86
>         select ARCH_WANT_GENERAL_HUGETLB
>         select ARCH_WANT_HUGE_PMD_SHARE
>         select ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP  if X86_64
> +       select ARCH_WANT_HUGETLB_HIGH_GRANULARITY_MAPPING

This needs `if X86_64` at the end. Will be corrected for v2.

>         select ARCH_WANT_LD_ORPHAN_WARN
>         select ARCH_WANTS_THP_SWAP              if X86_64
>         select ARCH_HAS_PARANOID_L1D_FLUSH
> --
> 2.39.0.314.g84b9a713c41-goog
>
diff mbox series

Patch

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 3604074a878b..3d08cd45549c 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -126,6 +126,7 @@  config X86
 	select ARCH_WANT_GENERAL_HUGETLB
 	select ARCH_WANT_HUGE_PMD_SHARE
 	select ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP	if X86_64
+	select ARCH_WANT_HUGETLB_HIGH_GRANULARITY_MAPPING
 	select ARCH_WANT_LD_ORPHAN_WARN
 	select ARCH_WANTS_THP_SWAP		if X86_64
 	select ARCH_HAS_PARANOID_L1D_FLUSH