Re: [RESEND PATCH V4 2/3] riscv: mm: Add soft-dirty page tracking support
From: Alexandre Ghiti
Date: Tue Nov 05 2024 - 08:15:16 EST
On 30/08/2024 04:31, Chunyan Zhang wrote:
Hi Jinjie,
On Fri, 30 Aug 2024 at 09:31, Jinjie Ruan <ruanjinjie@xxxxxxxxxx> wrote:
On 2024/8/30 9:11, Chunyan Zhang wrote:
The PTE bit(9) is reserved for software, now used by DEVMAP,
this patch reuse bit(9) for soft-dirty which is enabled only
if !CONFIG_ARCH_HAS_PTE_DEVMAP, in other words, soft-dirty
and devmap will be mutually exclusive on RISC-V.
To add swap PTE soft-dirty tracking, we borrow bit (4) which is
available for swap PTEs on RISC-V systems.
Signed-off-by: Chunyan Zhang <zhangchunyan@xxxxxxxxxxx>
---
arch/riscv/Kconfig | 27 ++++++++++-
arch/riscv/include/asm/pgtable-bits.h | 12 +++++
arch/riscv/include/asm/pgtable.h | 69 ++++++++++++++++++++++++++-
3 files changed, 106 insertions(+), 2 deletions(-)
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 0f3cd7c3a436..f1460fc01cd4 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -39,7 +39,6 @@ config RISCV
select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
select ARCH_HAS_PMEM_API
select ARCH_HAS_PREPARE_SYNC_CORE_CMD
- select ARCH_HAS_PTE_DEVMAP if 64BIT && MMU
select ARCH_HAS_PTE_SPECIAL
select ARCH_HAS_SET_DIRECT_MAP if MMU
select ARCH_HAS_SET_MEMORY if MMU
@@ -948,6 +947,32 @@ config RANDOMIZE_BASE
If unsure, say N.
+choice
+ prompt "PET RSW Bit(9) used for"
+ default RISCV_HAS_PTE_DEVMEP
+ depends on MMU && 64BIT
+ help
+ RISC-V PTE bit(9) is reserved for software, and used by more than
+ one kernel features which cannot be supported at the same time.
+ So we have to select one for it.
+
+config RISCV_HAS_PTE_DEVMEP
+ bool "DEVMAP mark"
+ select ARCH_HAS_PTE_DEVMAP
+ help
+ The PTE bit(9) is used for DEVMAP mark. ZONE_DEVICE pages need DEVMAP
+ PTEs support to function.
+
+ So if you want to use ZONE_DEVICE, select this.
+
+config RISCV_HAS_SOFT_DIRTY
+ bool "soft dirty"
+ select HAVE_ARCH_SOFT_DIRTY
+ help
+ The PTE bit(9) is used for soft-dirty tracking.
+
+endchoice
+
Hi, ARCH_HAS_PTE_DEVMAP will be removed in following patch, I guess
riscv will too:
https://lore.kernel.org/all/47c26640cd85f3db2e0a2796047199bb984d1b3f.1719386613.git-series.apopple@xxxxxxxxxx/
Thanks for sharing, I didn't notice this.
It looks like we should remove PTE_DEVMAP first and then add soft
dirty and uffd_wp.
I have not seen any progress in the removal of PTE_DEVMAP so I'd say we
should keep going with your patchset and we can still remove devmap later.
Thanks,
Alex
Thanks,
Chunyan
endmenu # "Kernel features"
menu "Boot options"
diff --git a/arch/riscv/include/asm/pgtable-bits.h b/arch/riscv/include/asm/pgtable-bits.h
index 5bcc73430829..c6d51fe9fc6f 100644
--- a/arch/riscv/include/asm/pgtable-bits.h
+++ b/arch/riscv/include/asm/pgtable-bits.h
@@ -26,6 +26,18 @@
#define _PAGE_DEVMAP 0
#endif /* CONFIG_ARCH_HAS_PTE_DEVMAP */
+#ifdef CONFIG_MEM_SOFT_DIRTY
+#define _PAGE_SOFT_DIRTY (1 << 9) /* RSW: 0x2 for software dirty tracking */
+/*
+ * BIT 4 is not involved into swap entry computation, so we
+ * can borrow it for swap page soft-dirty tracking.
+ */
+#define _PAGE_SWP_SOFT_DIRTY _PAGE_USER
+#else
+#define _PAGE_SOFT_DIRTY 0
+#define _PAGE_SWP_SOFT_DIRTY 0
+#endif /* CONFIG_MEM_SOFT_DIRTY */
+
#define _PAGE_TABLE _PAGE_PRESENT
/*
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 089f3c9f56a3..d41507919ef2 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -428,7 +428,7 @@ static inline pte_t pte_mkwrite_novma(pte_t pte)
static inline pte_t pte_mkdirty(pte_t pte)
{
- return __pte(pte_val(pte) | _PAGE_DIRTY);
+ return __pte(pte_val(pte) | _PAGE_DIRTY | _PAGE_SOFT_DIRTY);
}
static inline pte_t pte_mkclean(pte_t pte)
@@ -461,6 +461,38 @@ static inline pte_t pte_mkhuge(pte_t pte)
return pte;
}
+#ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY
+static inline int pte_soft_dirty(pte_t pte)
+{
+ return pte_val(pte) & _PAGE_SOFT_DIRTY;
+}
+
+static inline pte_t pte_mksoft_dirty(pte_t pte)
+{
+ return __pte(pte_val(pte) | _PAGE_SOFT_DIRTY);
+}
+
+static inline pte_t pte_clear_soft_dirty(pte_t pte)
+{
+ return __pte(pte_val(pte) & ~(_PAGE_SOFT_DIRTY));
+}
+
+static inline int pte_swp_soft_dirty(pte_t pte)
+{
+ return pte_val(pte) & _PAGE_SWP_SOFT_DIRTY;
+}
+
+static inline pte_t pte_swp_mksoft_dirty(pte_t pte)
+{
+ return __pte(pte_val(pte) | _PAGE_SWP_SOFT_DIRTY);
+}
+
+static inline pte_t pte_swp_clear_soft_dirty(pte_t pte)
+{
+ return __pte(pte_val(pte) & ~(_PAGE_SWP_SOFT_DIRTY));
+}
+#endif /* CONFIG_HAVE_ARCH_SOFT_DIRTY */
+
#ifdef CONFIG_RISCV_ISA_SVNAPOT
#define pte_leaf_size(pte) (pte_napot(pte) ? \
napot_cont_size(napot_cont_order(pte)) :\
@@ -751,6 +783,40 @@ static inline pmd_t pmd_mkdevmap(pmd_t pmd)
return pte_pmd(pte_mkdevmap(pmd_pte(pmd)));
}
+#ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY
+static inline int pmd_soft_dirty(pmd_t pmd)
+{
+ return pte_soft_dirty(pmd_pte(pmd));
+}
+
+static inline pmd_t pmd_mksoft_dirty(pmd_t pmd)
+{
+ return pte_pmd(pte_mksoft_dirty(pmd_pte(pmd)));
+}
+
+static inline pmd_t pmd_clear_soft_dirty(pmd_t pmd)
+{
+ return pte_pmd(pte_clear_soft_dirty(pmd_pte(pmd)));
+}
+
+#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
+static inline int pmd_swp_soft_dirty(pmd_t pmd)
+{
+ return pte_swp_soft_dirty(pmd_pte(pmd));
+}
+
+static inline pmd_t pmd_swp_mksoft_dirty(pmd_t pmd)
+{
+ return pte_pmd(pte_swp_mksoft_dirty(pmd_pte(pmd)));
+}
+
+static inline pmd_t pmd_swp_clear_soft_dirty(pmd_t pmd)
+{
+ return pte_pmd(pte_swp_clear_soft_dirty(pmd_pte(pmd)));
+}
+#endif /* CONFIG_ARCH_ENABLE_THP_MIGRATION */
+#endif /* CONFIG_HAVE_ARCH_SOFT_DIRTY */
+
static inline void set_pmd_at(struct mm_struct *mm, unsigned long addr,
pmd_t *pmdp, pmd_t pmd)
{
@@ -841,6 +907,7 @@ extern pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
* Format of swap PTE:
* bit 0: _PAGE_PRESENT (zero)
* bit 1 to 3: _PAGE_LEAF (zero)
+ * bit 4: _PAGE_SWP_SOFT_DIRTY
* bit 5: _PAGE_PROT_NONE (zero)
* bit 6: exclusive marker
* bits 7 to 11: swap type
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