| Message ID | 20201023091437.8225-3-miles.chen@mediatek.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm: support get_user_pages_fast | expand |
On Fri, Oct 23, 2020 at 05:14:35PM +0800, Miles Chen wrote: > From: Minchan Kim <minchan@kernel.org> > > To use bit 5 in page table as L_PTE_SPECIAL, we need a room for that. > It seems we don't need 4 bits for the memory type with ARMv6+. > If it's true, let's reorder bits to make bit 5 free. > > We will use the bit for L_PTE_SPECIAL in next patch. > > A note from Catalin in [1]: > " > > Anyway, on ARMv7 or ARMv6+LPAE, the non-shared device gets mapped to > > shared device in hardware. Looking through the arm32 code, it seems that > > MT_DEVICE_NONSHARED is used by arch/arm/mach-shmobile/setup-r8a7779.c > > and IIUC that's a v7 platform (R-Car H1, Cortex-A9). I think the above > > should be defined to L_PTE_MT_DEV_SHARED, unless I miss any place where > > DEV_NONSHARED is relevant on ARMv6 (adding Simon to confirm on shmbile). > " > > [1] https://lore.kernel.org/patchwork/patch/986574/ > > Cc: Russell King <linux@armlinux.org.uk> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will.deacon@arm.com> > Cc: Steve Capper <steve.capper@linaro.org> > Cc: Simon Horman <horms@verge.net.au> > Cc: Minchan Kim <minchan@kernel.org> > Cc: Suren Baghdasaryan <surenb@google.com> > Signed-off-by: Minchan Kim <minchan@kernel.org> > Signed-off-by: Miles Chen <miles.chen@mediatek.com> > --- > arch/arm/include/asm/pgtable-2level.h | 21 +++++++++++++++++---- > arch/arm/mm/proc-macros.S | 4 ++-- > 2 files changed, 19 insertions(+), 6 deletions(-) > > diff --git a/arch/arm/include/asm/pgtable-2level.h b/arch/arm/include/asm/pgtable-2level.h > index 27a8635abea0..cdcd55cca37d 100644 > --- a/arch/arm/include/asm/pgtable-2level.h > +++ b/arch/arm/include/asm/pgtable-2level.h > @@ -161,14 +161,27 @@ > #define L_PTE_MT_BUFFERABLE (_AT(pteval_t, 0x01) << 2) /* 0001 */ > #define L_PTE_MT_WRITETHROUGH (_AT(pteval_t, 0x02) << 2) /* 0010 */ > #define L_PTE_MT_WRITEBACK (_AT(pteval_t, 0x03) << 2) /* 0011 */ > +#define L_PTE_MT_DEV_SHARED (_AT(pteval_t, 0x04) << 2) /* 0100 */ > +#define L_PTE_MT_VECTORS (_AT(pteval_t, 0x05) << 2) /* 0101 */ > #define L_PTE_MT_MINICACHE (_AT(pteval_t, 0x06) << 2) /* 0110 (sa1100, xscale) */ > #define L_PTE_MT_WRITEALLOC (_AT(pteval_t, 0x07) << 2) /* 0111 */ > -#define L_PTE_MT_DEV_SHARED (_AT(pteval_t, 0x04) << 2) /* 0100 */ > -#define L_PTE_MT_DEV_NONSHARED (_AT(pteval_t, 0x0c) << 2) /* 1100 */ Sorry, no, this isn't going to work. The lower two bits of this (bits 2 and 3) are explicitly designed to fit the C and B bits used in older architectures. Changing L_PTE_MT_VECTORS from having value '11' to '01' changes the functionality on older CPUs.
On Fri, 2020-10-23 at 11:16 +0100, Russell King - ARM Linux admin wrote: > On Fri, Oct 23, 2020 at 05:14:35PM +0800, Miles Chen wrote: > > From: Minchan Kim <minchan@kernel.org> > > > > To use bit 5 in page table as L_PTE_SPECIAL, we need a room for that. > > It seems we don't need 4 bits for the memory type with ARMv6+. > > If it's true, let's reorder bits to make bit 5 free. > > > > We will use the bit for L_PTE_SPECIAL in next patch. > > > > A note from Catalin in [1]: > > " > > > Anyway, on ARMv7 or ARMv6+LPAE, the non-shared device gets mapped to > > > shared device in hardware. Looking through the arm32 code, it seems that > > > MT_DEVICE_NONSHARED is used by arch/arm/mach-shmobile/setup-r8a7779.c > > > and IIUC that's a v7 platform (R-Car H1, Cortex-A9). I think the above > > > should be defined to L_PTE_MT_DEV_SHARED, unless I miss any place where > > > DEV_NONSHARED is relevant on ARMv6 (adding Simon to confirm on shmbile). > > " > > > > [1] https://lore.kernel.org/patchwork/patch/986574/ > > > > Cc: Russell King <linux@armlinux.org.uk> > > Cc: Catalin Marinas <catalin.marinas@arm.com> > > Cc: Will Deacon <will.deacon@arm.com> > > Cc: Steve Capper <steve.capper@linaro.org> > > Cc: Simon Horman <horms@verge.net.au> > > Cc: Minchan Kim <minchan@kernel.org> > > Cc: Suren Baghdasaryan <surenb@google.com> > > Signed-off-by: Minchan Kim <minchan@kernel.org> > > Signed-off-by: Miles Chen <miles.chen@mediatek.com> > > --- > > arch/arm/include/asm/pgtable-2level.h | 21 +++++++++++++++++---- > > arch/arm/mm/proc-macros.S | 4 ++-- > > 2 files changed, 19 insertions(+), 6 deletions(-) > > > > diff --git a/arch/arm/include/asm/pgtable-2level.h b/arch/arm/include/asm/pgtable-2level.h > > index 27a8635abea0..cdcd55cca37d 100644 > > --- a/arch/arm/include/asm/pgtable-2level.h > > +++ b/arch/arm/include/asm/pgtable-2level.h > > @@ -161,14 +161,27 @@ > > #define L_PTE_MT_BUFFERABLE (_AT(pteval_t, 0x01) << 2) /* 0001 */ > > #define L_PTE_MT_WRITETHROUGH (_AT(pteval_t, 0x02) << 2) /* 0010 */ > > #define L_PTE_MT_WRITEBACK (_AT(pteval_t, 0x03) << 2) /* 0011 */ > > +#define L_PTE_MT_DEV_SHARED (_AT(pteval_t, 0x04) << 2) /* 0100 */ > > +#define L_PTE_MT_VECTORS (_AT(pteval_t, 0x05) << 2) /* 0101 */ > > #define L_PTE_MT_MINICACHE (_AT(pteval_t, 0x06) << 2) /* 0110 (sa1100, xscale) */ > > #define L_PTE_MT_WRITEALLOC (_AT(pteval_t, 0x07) << 2) /* 0111 */ > > -#define L_PTE_MT_DEV_SHARED (_AT(pteval_t, 0x04) << 2) /* 0100 */ > > -#define L_PTE_MT_DEV_NONSHARED (_AT(pteval_t, 0x0c) << 2) /* 1100 */ > > Sorry, no, this isn't going to work. > > The lower two bits of this (bits 2 and 3) are explicitly designed to fit > the C and B bits used in older architectures. Changing L_PTE_MT_VECTORS > from having value '11' to '01' changes the functionality on older CPUs. > thanks for the comment. Is is possible to find other order to fit this? e.g., +#define L_PTE_MT_VECTORS (_AT(pteval_t, 0x07) << 2) /* 0111 */ #define L_PTE_MT_WRITEALLOC (_AT(pteval_t, 0x05) << 2) /* 0101 */ or only allow this types for the new CPUs? Miles
diff --git a/arch/arm/include/asm/pgtable-2level.h b/arch/arm/include/asm/pgtable-2level.h index 27a8635abea0..cdcd55cca37d 100644 --- a/arch/arm/include/asm/pgtable-2level.h +++ b/arch/arm/include/asm/pgtable-2level.h @@ -161,14 +161,27 @@ #define L_PTE_MT_BUFFERABLE (_AT(pteval_t, 0x01) << 2) /* 0001 */ #define L_PTE_MT_WRITETHROUGH (_AT(pteval_t, 0x02) << 2) /* 0010 */ #define L_PTE_MT_WRITEBACK (_AT(pteval_t, 0x03) << 2) /* 0011 */ +#define L_PTE_MT_DEV_SHARED (_AT(pteval_t, 0x04) << 2) /* 0100 */ +#define L_PTE_MT_VECTORS (_AT(pteval_t, 0x05) << 2) /* 0101 */ #define L_PTE_MT_MINICACHE (_AT(pteval_t, 0x06) << 2) /* 0110 (sa1100, xscale) */ #define L_PTE_MT_WRITEALLOC (_AT(pteval_t, 0x07) << 2) /* 0111 */ -#define L_PTE_MT_DEV_SHARED (_AT(pteval_t, 0x04) << 2) /* 0100 */ -#define L_PTE_MT_DEV_NONSHARED (_AT(pteval_t, 0x0c) << 2) /* 1100 */ +#if defined(CONFIG_CPU_V7) || defined(CONFIG_CPU_V6) || defined(CONFIG_CPU_V6K) +/* + * On ARMv7 or ARMv7+LPAE, the non-shared and shared device types get + * mapped to the same TEX remapping index. On classic ARMv7, the + * shareability is controlled by the PRRR[17:16] field, indexed by + * L_PTE_SHARED. On ARMv7+LPAE the device mapping is always shareable. + */ +#define L_PTE_MT_DEV_NONSHARED L_PTE_MT_DEV_SHARED +#define L_PTE_MT_DEV_WC L_PTE_MT_BUFFERABLE +#define L_PTE_MT_DEV_CACHED L_PTE_MT_WRITEBACK +#define L_PTE_MT_MASK (_AT(pteval_t, 0x07) << 2) +#else #define L_PTE_MT_DEV_WC (_AT(pteval_t, 0x09) << 2) /* 1001 */ #define L_PTE_MT_DEV_CACHED (_AT(pteval_t, 0x0b) << 2) /* 1011 */ -#define L_PTE_MT_VECTORS (_AT(pteval_t, 0x0f) << 2) /* 1111 */ -#define L_PTE_MT_MASK (_AT(pteval_t, 0x0f) << 2) +#define L_PTE_MT_DEV_NONSHARED (_AT(pteval_t, 0x0c) << 2) /* 1100 */ +#define L_PTE_MT_MASK (_AT(pteval_t, 0x0f) << 2) +#endif #ifndef __ASSEMBLY__ diff --git a/arch/arm/mm/proc-macros.S b/arch/arm/mm/proc-macros.S index e2c743aa2eb2..dde1d6374250 100644 --- a/arch/arm/mm/proc-macros.S +++ b/arch/arm/mm/proc-macros.S @@ -137,7 +137,7 @@ .long PTE_CACHEABLE @ L_PTE_MT_WRITETHROUGH .long PTE_CACHEABLE | PTE_BUFFERABLE @ L_PTE_MT_WRITEBACK .long PTE_BUFFERABLE @ L_PTE_MT_DEV_SHARED - .long 0x00 @ unused + .long PTE_CACHEABLE | PTE_BUFFERABLE | PTE_EXT_APX @ L_PTE_MT_VECTORS .long 0x00 @ L_PTE_MT_MINICACHE (not present) .long PTE_EXT_TEX(1) | PTE_CACHEABLE | PTE_BUFFERABLE @ L_PTE_MT_WRITEALLOC .long 0x00 @ unused @@ -147,7 +147,7 @@ .long PTE_EXT_TEX(2) @ L_PTE_MT_DEV_NONSHARED .long 0x00 @ unused .long 0x00 @ unused - .long PTE_CACHEABLE | PTE_BUFFERABLE | PTE_EXT_APX @ L_PTE_MT_VECTORS + .long 0x00 @ unused .endm .macro armv6_set_pte_ext pfx