Re: [PATCH 05/12] mm: enable MMU_GATHER_RCU_TABLE_FREE for arc, microblaze, xtensa

On Mon, Sep 07, 2026 at 02:07:37PM -0700, Suren Baghdasaryan wrote:

On Tue, Sep 1, 2026 at 4:06 AM Lorenzo Stoakes (ARM) [off-list ref] wrote:

quoted

Each of these architectures directly free page tables without routing these
changes through tlb_remove_ptdesc().

The use of tlb_remove_ptdesc() is required for
CONFIG_MMU_GATHER_RCU_TABLE_FREE to correctly free page tables under RCU,
so simply update these architectures to use these functions.

Since none of the architectures share page tables or do anything unusual,
nothing complicated is required here.

Therefore this is simply a mechanical change - convert __pud_free_tlb(),
__pmd_free_tlb() and __pte_free_tlb() to use tlb_remove_ptdesc() as
required.

At the point this is in place, all mmu_gather page table freeing is
performed under RCU, and thus MMU_GATHER_RCU_TABLE_FREE is selected for
each architecture.

This forms part of an overall effort to switch every architecture to this
mode.

Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
---
 arch/arc/Kconfig                      | 1 +
 arch/arc/include/asm/pgalloc.h        | 6 +++---
 arch/microblaze/Kconfig               | 1 +
 arch/microblaze/include/asm/pgalloc.h | 2 +-
 arch/xtensa/Kconfig                   | 1 +
 arch/xtensa/include/asm/tlb.h         | 2 +-
 6 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index 2ed7186c81c5..7a7542b61823 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig

@@ -47,6 +47,7 @@ config ARC
        select HAVE_SYSCALL_TRACEPOINTS
        select IRQ_DOMAIN
        select LOCK_MM_AND_FIND_VMA
+       select MMU_GATHER_RCU_TABLE_FREE
        select MODULES_USE_ELF_RELA
        select OF
        select OF_EARLY_FLATTREE

diff --git a/arch/arc/include/asm/pgalloc.h b/arch/arc/include/asm/pgalloc.h
index dfae070fe8d5..9b6c37f92e97 100644
--- a/arch/arc/include/asm/pgalloc.h
+++ b/arch/arc/include/asm/pgalloc.h

@@ -72,7 +72,7 @@ static inline void p4d_populate(struct mm_struct *mm, p4d_t *p4dp, pud_t *pudp)
        set_p4d(p4dp, __p4d((unsigned long)pudp));
 }

-#define __pud_free_tlb(tlb, pmd, addr)  pud_free((tlb)->mm, pmd)
+#define __pud_free_tlb(tlb, pmd, addr)  tlb_remove_ptdesc((tlb), virt_to_ptdesc(pmd))

 #endif

@@ -83,10 +83,10 @@ static inline void pud_populate(struct mm_struct *mm, pud_t *pudp, pmd_t *pmdp)
        set_pud(pudp, __pud((unsigned long)pmdp));
 }

-#define __pmd_free_tlb(tlb, pmd, addr)  pmd_free((tlb)->mm, pmd)
+#define __pmd_free_tlb(tlb, pmd, addr)  tlb_remove_ptdesc((tlb), virt_to_ptdesc(pmd))

 #endif

-#define __pte_free_tlb(tlb, pte, addr)  pte_free((tlb)->mm, pte)
+#define __pte_free_tlb(tlb, pte, addr)  tlb_remove_ptdesc((tlb), page_ptdesc(pte))

 #endif /* _ASM_ARC_PGALLOC_H */

diff --git a/arch/microblaze/Kconfig b/arch/microblaze/Kconfig
index 484ebb3baedf..af7e821e96c1 100644
--- a/arch/microblaze/Kconfig
+++ b/arch/microblaze/Kconfig

@@ -41,6 +41,7 @@ config MICROBLAZE
        select PCI_SYSCALL if PCI
        select CPU_NO_EFFICIENT_FFS
        select MMU_GATHER_NO_RANGE
+       select MMU_GATHER_RCU_TABLE_FREE
        select SPARSE_IRQ
        select ZONE_DMA
        select TRACE_IRQFLAGS_SUPPORT

diff --git a/arch/microblaze/include/asm/pgalloc.h b/arch/microblaze/include/asm/pgalloc.h
index 084a8a0dc239..ffee6a009219 100644
--- a/arch/microblaze/include/asm/pgalloc.h
+++ b/arch/microblaze/include/asm/pgalloc.h

@@ -25,7 +25,7 @@ extern void __bad_pte(pmd_t *pmd);

 extern pte_t *pte_alloc_one_kernel(struct mm_struct *mm);

-#define __pte_free_tlb(tlb, pte, addr) pte_free((tlb)->mm, (pte))
+#define __pte_free_tlb(tlb, pte, addr) tlb_remove_ptdesc((tlb), page_ptdesc(pte))

 #define pmd_populate(mm, pmd, pte) \
                        (pmd_val(*(pmd)) = (unsigned long)page_address(pte))

diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig
index f2f9cd9cde50..33c4caee30e2 100644
--- a/arch/xtensa/Kconfig
+++ b/arch/xtensa/Kconfig

@@ -55,6 +55,7 @@ config XTENSA
        select HAVE_VIRT_CPU_ACCOUNTING_GEN
        select IRQ_DOMAIN
        select LOCK_MM_AND_FIND_VMA
+       select MMU_GATHER_RCU_TABLE_FREE if MMU

And MMU is required because NOMMU does not perform mmu_gather
operations, same as in the previous patch? If so, maybe make a note of
it in the changelog?

Right yup. Will update!

quoted

        select MODULES_USE_ELF_RELA
        select PERF_USE_VMALLOC
        select TRACE_IRQFLAGS_SUPPORT

diff --git a/arch/xtensa/include/asm/tlb.h b/arch/xtensa/include/asm/tlb.h
index 8c3ceb427018..6fb7b78154f6 100644
--- a/arch/xtensa/include/asm/tlb.h
+++ b/arch/xtensa/include/asm/tlb.h

@@ -16,7 +16,7 @@

 #include <asm-generic/tlb.h>

-#define __pte_free_tlb(tlb, pte, address)      pte_free((tlb)->mm, pte)
+#define __pte_free_tlb(tlb, pte, address)      tlb_remove_ptdesc((tlb), page_ptdesc(pte))

 void check_tlb_sanity(void);


--

2.55.0

--
Cheers, Lorenzo