[PATCH 0/2] Enable ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP & fixup race condition on PG_dcache_clean

[PATCH 0/2] Enable ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP & fixup race condition on PG_dcache_clean

[guoren]

From: Guo Ren <guoren@linux.alibaba.com>

The first patch fixup race condition on PG_dcache_clean which found in
arm64. Then enable ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP and tested
with simple hugetlbfs test case.

# cat /proc/sys/vm/hugetlb_optimize_vmemmap
1
# echo 8 > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages
# mount -t hugetlbfs none test/ -o pagesize=2048k
# ./myhugemap_test
# umount test/
# echo 0 > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages

No problem found.

Guo Ren (2):
  riscv: Fixup race condition on PG_dcache_clean in flush_icache_pte
  riscv: Enable ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP

 arch/riscv/Kconfig                  | 1 +
 arch/riscv/include/asm/cacheflush.h | 3 +++
 arch/riscv/mm/cacheflush.c          | 7 ++++++-
 3 files changed, 10 insertions(+), 1 deletion(-)

-- 
2.36.1


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[PATCH 1/2] riscv: Fixup race condition on PG_dcache_clean in flush_icache_pte

[guoren]

From: Guo Ren <guoren@linux.alibaba.com>

RISC-V follows the arm64 flush_icache_pte mechanism and also includes
its bug. The patch ensures that instructions are observable in a new
mapping. For more details, see 588a513d3425 ("arm64: Fix race condition
on PG_dcache_clean in __sync_icache_dcache()").

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Steven Price <steven.price@arm.com>
---
 arch/riscv/mm/cacheflush.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c
index 6cb7d96ad9c7..7c9f97fa3938 100644
--- a/arch/riscv/mm/cacheflush.c
+++ b/arch/riscv/mm/cacheflush.c
@@ -82,7 +82,9 @@ void flush_icache_pte(pte_t pte)
 {
 	struct page *page = pte_page(pte);
 
-	if (!test_and_set_bit(PG_dcache_clean, &page->flags))
+	if (!test_bit(PG_dcache_clean, &page->flags)) {
 		flush_icache_all();
+		set_bit(PG_dcache_clean, &page->flags);
+	}
 }
 #endif /* CONFIG_MMU */
-- 
2.36.1


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[PATCH 2/2] riscv: Enable ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP

[guoren]

From: Guo Ren <guoren@linux.alibaba.com>

This patch enable the feature of "free some vmemmap pages of HugeTLB
page" [1]. To make it work correct, we also need fixup PG_dcache_clean
setting for huge page [2].

[1] https://lore.kernel.org/linux-doc/20210510030027.56044-1-songmuchun@bytedance.com/
[2] https://lore.kernel.org/linux-mm/20220302084624.33340-1-songmuchun@bytedance.com/

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Huacai Chen <chenhuacai@loongson.cn>
Cc: Arnd Bergmann <arnd@arndb.de>
---
 arch/riscv/Kconfig                  | 1 +
 arch/riscv/include/asm/cacheflush.h | 3 +++
 arch/riscv/mm/cacheflush.c          | 3 +++
 3 files changed, 7 insertions(+)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 6b48a3ae9843..81ac25b0e005 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -45,6 +45,7 @@ config RISCV
 	select ARCH_WANT_FRAME_POINTERS
 	select ARCH_WANT_GENERAL_HUGETLB
 	select ARCH_WANT_HUGE_PMD_SHARE if 64BIT
+	select ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
 	select ARCH_WANTS_THP_SWAP if HAVE_ARCH_TRANSPARENT_HUGEPAGE
 	select BINFMT_FLAT_NO_DATA_START_OFFSET if !MMU
 	select BUILDTIME_TABLE_SORT if MMU
diff --git a/arch/riscv/include/asm/cacheflush.h b/arch/riscv/include/asm/cacheflush.h
index 8a5c246b0a21..96f7381aeeeb 100644
--- a/arch/riscv/include/asm/cacheflush.h
+++ b/arch/riscv/include/asm/cacheflush.h
@@ -17,6 +17,9 @@ static inline void local_flush_icache_all(void)
 
 static inline void flush_dcache_page(struct page *page)
 {
+	if (PageHuge(page))
+		page = compound_head(page);
+
 	if (test_bit(PG_dcache_clean, &page->flags))
 		clear_bit(PG_dcache_clean, &page->flags);
 }
diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c
index 7c9f97fa3938..ca35807cf185 100644
--- a/arch/riscv/mm/cacheflush.c
+++ b/arch/riscv/mm/cacheflush.c
@@ -82,6 +82,9 @@ void flush_icache_pte(pte_t pte)
 {
 	struct page *page = pte_page(pte);
 
+	if (PageHuge(page))
+		page = compound_head(page);
+
 	if (!test_bit(PG_dcache_clean, &page->flags)) {
 		flush_icache_all();
 		set_bit(PG_dcache_clean, &page->flags);
-- 
2.36.1


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Re: [PATCH 2/2] riscv: Enable ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP

[Muchun Song]

> On Oct 23, 2022, at 21:32, guoren@kernel.org wrote:
> 
> From: Guo Ren <guoren@linux.alibaba.com>
> 
> This patch enable the feature of "free some vmemmap pages of HugeTLB

We have a new name “HVO" to refer to this feature. So I’d like to rewrite
The changelog to something like “Enable HVO [1] for RISCV”.

> page" [1]. To make it work correct, we also need fixup PG_dcache_clean
> setting for huge page [2].
> 
> [1] https://lore.kernel.org/linux-doc/20210510030027.56044-1-songmuchun@bytedance.com/
> [2] https://lore.kernel.org/linux-mm/20220302084624.33340-1-songmuchun@bytedance.com/
> 
> Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> Signed-off-by: Guo Ren <guoren@kernel.org>
> Cc: Muchun Song <songmuchun@bytedance.com>
> Cc: Huacai Chen <chenhuacai@loongson.cn>
> Cc: Arnd Bergmann <arnd@arndb.de>

I’am really glad to see more and more arches for support HVO.

Acked-by: Muchun Song <songmuchun@bytedance.com>

Thanks.


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Re: [PATCH 2/2] riscv: Enable ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP

[Guo Ren]

On Mon, Oct 24, 2022 at 3:07 PM Muchun Song <muchun.song@linux.dev> wrote:
>
>
>
> > On Oct 23, 2022, at 21:32, guoren@kernel.org wrote:
> >
> > From: Guo Ren <guoren@linux.alibaba.com>
> >
> > This patch enable the feature of "free some vmemmap pages of HugeTLB
>
> We have a new name “HVO" to refer to this feature. So I’d like to rewrite
> The changelog to something like “Enable HVO [1] for RISCV”.
Okay.

>
> > page" [1]. To make it work correct, we also need fixup PG_dcache_clean
> > setting for huge page [2].
> >
> > [1] https://lore.kernel.org/linux-doc/20210510030027.56044-1-songmuchun@bytedance.com/
> > [2] https://lore.kernel.org/linux-mm/20220302084624.33340-1-songmuchun@bytedance.com/
> >
> > Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> > Signed-off-by: Guo Ren <guoren@kernel.org>
> > Cc: Muchun Song <songmuchun@bytedance.com>
> > Cc: Huacai Chen <chenhuacai@loongson.cn>
> > Cc: Arnd Bergmann <arnd@arndb.de>
>
> I’am really glad to see more and more arches for support HVO.
>
> Acked-by: Muchun Song <songmuchun@bytedance.com>
Thx

>
> Thanks.
>


-- 
Best Regards
 Guo Ren

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