| Message ID | 20240918061702.614837-1-tiwei.btw@antgroup.com |
|---|---|
| State | New |
| Headers | show |
| Series | um: Remove 3-level page table support on i386 | expand |
On Wed, 2024-09-18 at 14:17 +0800, Tiwei Bie wrote: > The highmem support has been removed by commit a98a6d864d3b ("um: > Remove broken highmem support"). The 2-level page table is sufficient > on UML/i386 now. Remove the 3-level page table support on UML/i386 > which is still marked as experimental. > No real objection, but with the 4-level page table work on 64-bit pending as well (which likely conflicts), I wonder if we should just remove 3-level *entirely*? johannes
On Thu, 2024-09-19 at 08:54 +0200, Johannes Berg wrote: > On Wed, 2024-09-18 at 14:17 +0800, Tiwei Bie wrote: > > The highmem support has been removed by commit a98a6d864d3b ("um: > > Remove broken highmem support"). The 2-level page table is > > sufficient > > on UML/i386 now. Remove the 3-level page table support on UML/i386 > > which is still marked as experimental. > > > > No real objection, but with the 4-level page table work on 64-bit > pending as well (which likely conflicts), I wonder if we should just > remove 3-level *entirely*? Fine with me. There is only the tiny advantage of saving a few pages of memory for each process. I just erred on the side of keeping it in case anyone is cares to the option … I'll resubmit the patchset without 3-level support then, possibly on top of this patch. On the assumption that no one actually cares about 3-level page tables on x86_64. Benjamin
On 2024/9/19 15:22, Benjamin Berg wrote: > On Thu, 2024-09-19 at 08:54 +0200, Johannes Berg wrote: >> On Wed, 2024-09-18 at 14:17 +0800, Tiwei Bie wrote: >>> The highmem support has been removed by commit a98a6d864d3b ("um: >>> Remove broken highmem support"). The 2-level page table is >>> sufficient >>> on UML/i386 now. Remove the 3-level page table support on UML/i386 >>> which is still marked as experimental. >>> >> >> No real objection, but with the 4-level page table work on 64-bit >> pending as well (which likely conflicts), I wonder if we should just >> remove 3-level *entirely*? Fine with me in either way. Keeping only one page table implementation on UML/x86_64 may require smaller maintenance effort. > > Fine with me. There is only the tiny advantage of saving a few pages of > memory for each process. I just erred on the side of keeping it in case > anyone is cares to the option … > > I'll resubmit the patchset without 3-level support then, possibly on > top of this patch. Thanks! :) Regards, Tiwei > On the assumption that no one actually cares about > 3-level page tables on x86_64. > > Benjamin
diff --git a/arch/um/configs/i386_defconfig b/arch/um/configs/i386_defconfig index e543cbac8792..0cc717d80be6 100644 --- a/arch/um/configs/i386_defconfig +++ b/arch/um/configs/i386_defconfig @@ -1,4 +1,3 @@ -CONFIG_3_LEVEL_PGTABLES=y # CONFIG_COMPACTION is not set CONFIG_BINFMT_MISC=m CONFIG_HOSTFS=y diff --git a/arch/um/include/asm/page.h b/arch/um/include/asm/page.h index 9ef9a8aedfa6..8d2ac5e86cf5 100644 --- a/arch/um/include/asm/page.h +++ b/arch/um/include/asm/page.h @@ -32,28 +32,6 @@ struct page; #define clear_user_page(page, vaddr, pg) clear_page(page) #define copy_user_page(to, from, vaddr, pg) copy_page(to, from) -#if defined(CONFIG_3_LEVEL_PGTABLES) && !defined(CONFIG_64BIT) - -typedef struct { unsigned long pte; } pte_t; -typedef struct { unsigned long pmd; } pmd_t; -typedef struct { unsigned long pgd; } pgd_t; -#define pte_val(p) ((p).pte) - -#define pte_get_bits(p, bits) ((p).pte & (bits)) -#define pte_set_bits(p, bits) ((p).pte |= (bits)) -#define pte_clear_bits(p, bits) ((p).pte &= ~(bits)) -#define pte_copy(to, from) ({ (to).pte = (from).pte; }) -#define pte_is_zero(p) (!((p).pte & ~_PAGE_NEWPAGE)) -#define pte_set_val(p, phys, prot) \ - ({ (p).pte = (phys) | pgprot_val(prot); }) - -#define pmd_val(x) ((x).pmd) -#define __pmd(x) ((pmd_t) { (x) } ) - -typedef unsigned long long phys_t; - -#else - typedef struct { unsigned long pte; } pte_t; typedef struct { unsigned long pgd; } pgd_t; @@ -75,8 +53,6 @@ typedef struct { unsigned long pmd; } pmd_t; typedef unsigned long phys_t; -#endif - typedef struct { unsigned long pgprot; } pgprot_t; typedef struct page *pgtable_t; diff --git a/arch/um/include/asm/pgtable-3level.h b/arch/um/include/asm/pgtable-3level.h index 8a5032ec231f..3504a92dc485 100644 --- a/arch/um/include/asm/pgtable-3level.h +++ b/arch/um/include/asm/pgtable-3level.h @@ -11,11 +11,7 @@ /* PGDIR_SHIFT determines what a third-level page table entry can map */ -#ifdef CONFIG_64BIT #define PGDIR_SHIFT 30 -#else -#define PGDIR_SHIFT 31 -#endif #define PGDIR_SIZE (1UL << PGDIR_SHIFT) #define PGDIR_MASK (~(PGDIR_SIZE-1)) @@ -32,13 +28,8 @@ */ #define PTRS_PER_PTE 512 -#ifdef CONFIG_64BIT #define PTRS_PER_PMD 512 #define PTRS_PER_PGD 512 -#else -#define PTRS_PER_PMD 1024 -#define PTRS_PER_PGD 1024 -#endif #define USER_PTRS_PER_PGD ((TASK_SIZE + (PGDIR_SIZE - 1)) / PGDIR_SIZE) diff --git a/arch/x86/um/Kconfig b/arch/x86/um/Kconfig index 186f13268401..7d16baba8f5f 100644 --- a/arch/x86/um/Kconfig +++ b/arch/x86/um/Kconfig @@ -29,15 +29,7 @@ config X86_64 select MODULES_USE_ELF_RELA config 3_LEVEL_PGTABLES - bool "Three-level pagetables" if !64BIT - default 64BIT - help - Three-level pagetables will let UML have more than 4G of physical - memory. All the memory that can't be mapped directly will be treated - as high memory. - - However, this it experimental on 32-bit architectures, so if unsure say - N (on x86-64 it's automatically enabled, instead, as it's safe there). + def_bool 64BIT config ARCH_HAS_SC_SIGNALS def_bool !64BIT
The highmem support has been removed by commit a98a6d864d3b ("um: Remove broken highmem support"). The 2-level page table is sufficient on UML/i386 now. Remove the 3-level page table support on UML/i386 which is still marked as experimental. Suggested-by: Benjamin Berg <benjamin@sipsolutions.net> Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com> --- arch/um/configs/i386_defconfig | 1 - arch/um/include/asm/page.h | 24 ------------------------ arch/um/include/asm/pgtable-3level.h | 9 --------- arch/x86/um/Kconfig | 10 +--------- 4 files changed, 1 insertion(+), 43 deletions(-)