linux-kernel - [RFC PATCH v2 40/47] hugetlb: x86: enable high-granularity mapping

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Message-ID: <20221021163703.3218176-41-jthoughton@google.com>
Date:   Fri, 21 Oct 2022 16:36:56 +0000
From:   James Houghton <jthoughton@...gle.com>
To:     Mike Kravetz <mike.kravetz@...cle.com>,
        Muchun Song <songmuchun@...edance.com>,
        Peter Xu <peterx@...hat.com>
Cc:     David Hildenbrand <david@...hat.com>,
        David Rientjes <rientjes@...gle.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Mina Almasry <almasrymina@...gle.com>,
        "Zach O'Keefe" <zokeefe@...gle.com>,
        Manish Mishra <manish.mishra@...anix.com>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Yang Shi <shy828301@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        James Houghton <jthoughton@...gle.com>
Subject: [RFC PATCH v2 40/47] hugetlb: x86: enable high-granularity mapping

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@...gle.com>
---
 arch/x86/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 6d1879ef933a..6d7103266e61 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -124,6 +124,7 @@ 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
-- 
2.38.0.135.g90850a2211-goog