[PATCH] riscv: Add RISC-V svpbmt extension
Anup Patel
anup at brainfault.org
Thu Sep 23 02:13:14 PDT 2021
On Thu, Sep 23, 2021 at 12:57 PM <guoren at kernel.org> wrote:
>
> From: Guo Ren <guoren at linux.alibaba.com>
>
> This patch follows the standard pure RISC-V Svpbmt extension in
> privilege spec to solve the non-coherent SOC dma synchronization
> issues.
>
> Here is the svpbmt PTE format:
> | 63 | 62-61 | 60-8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0
> N MT RSW D A G U X W R V
> ^
>
> Of the Reserved bits [63:54] in a leaf PTE, the high bit is already
> allocated (as the N bit), so bits [62:61] are used as the MT (aka
> MemType) field. This field specifies one of three memory types that
> are close equivalents (or equivalent in effect) to the three main x86
> and ARMv8 memory types - as shown in the following table.
>
> RISC-V
> Encoding &
> MemType RISC-V Description
> ---------- ------------------------------------------------
> 00 - PMA Normal Cacheable, No change to implied PMA memory type
> 01 - NC Non-cacheable, idempotent, weakly-ordered Main Memory
> 10 - IO Non-cacheable, non-idempotent, strongly-ordered I/O memory
> 11 - Rsvd Reserved for future standard use
>
> The standard protection_map [] needn't be modified because the "PMA"
> type keeps the highest bits zero. The standard protection_map[] needn't
> be modified. So the whole modification is in the arch/riscv pgtable and
> using a global variable (__riscv_svpbmt) in the _PAGE_DMA_MASK/IO/NC
> for pgprot_noncached (&writecombine). We also need _PAGE_CHG_MASK to
> detect PFN than before.
>
> Devicetree: reuse "mmu-type" of cpu_section as a user interface to
> enable the feature or not:
> - riscv,sv39,svpbmt
> - riscv,sv48,svpbmt
>
> Signed-off-by: Guo Ren <guoren at linux.alibaba.com>
> Cc: Liu Shaohua <liush at allwinnertech.com>
> Cc: Wei Fu <wefu at redhat.com>
> Cc: Palmer Dabbelt <palmerdabbelt at google.com>
> Cc: Christoph Hellwig <hch at lst.de>
> Cc: Anup Patel <anup.patel at wdc.com>
> Cc: Arnd Bergmann <arnd at arndb.de>
> Cc: Atish Patra <atish.patra at wdc.com>
> Cc: Drew Fustini <drew at beagleboard.org>
> Cc: Wei Fu <wefu at redhat.com>
> Cc: Wei Wu <lazyparser at gmail.com>
> Cc: Chen-Yu Tsai <wens at csie.org>
> Cc: Maxime Ripard <maxime at cerno.tech>
> Cc: Daniel Lustig <dlustig at nvidia.com>
> Cc: Greg Favor <gfavor at ventanamicro.com>
> Cc: Andrea Mondelli <andrea.mondelli at huawei.com>
> Cc: Jonathan Behrens <behrensj at mit.edu>
> Cc: Xinhaoqu (Freddie) <xinhaoqu at huawei.com>
> Cc: Bill Huffman <huffman at cadence.com>
> Cc: Nick Kossifidis <mick at ics.forth.gr>
> Cc: Allen Baum <allen.baum at esperantotech.com>
> Cc: Josh Scheid <jscheid at ventanamicro.com>
> Cc: Richard Trauben <rtrauben at gmail.com>
> ---
> .../devicetree/bindings/riscv/cpus.yaml | 2 +
> arch/riscv/include/asm/fixmap.h | 2 +-
> arch/riscv/include/asm/pgtable-64.h | 8 ++--
> arch/riscv/include/asm/pgtable-bits.h | 46 ++++++++++++++++++-
> arch/riscv/include/asm/pgtable.h | 39 ++++++++++++----
> arch/riscv/include/asm/processor.h | 1 +
> arch/riscv/kernel/cpufeature.c | 23 ++++++++++
> arch/riscv/kernel/setup.c | 2 +
> arch/riscv/mm/init.c | 5 ++
> 9 files changed, 113 insertions(+), 15 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/riscv/cpus.yaml b/Documentation/devicetree/bindings/riscv/cpus.yaml
> index e534f6a7cfa1..1825cd8db0de 100644
> --- a/Documentation/devicetree/bindings/riscv/cpus.yaml
> +++ b/Documentation/devicetree/bindings/riscv/cpus.yaml
> @@ -56,7 +56,9 @@ properties:
> enum:
> - riscv,sv32
> - riscv,sv39
> + - riscv,sv39,svpbmt
> - riscv,sv48
> + - riscv,sv48,svpbmt
> - riscv,none
I think augmenting the "mmu-type" DT property is a good approach but the
description of "mmu-type" DT property needs to say:
"Identifies the MMU address translation mode and page based memory
type used on ..."
Also, DT bindings change is generally a separate patch so better to make
a separate patch for this.
>
> riscv,isa:
> diff --git a/arch/riscv/include/asm/fixmap.h b/arch/riscv/include/asm/fixmap.h
> index 54cbf07fb4e9..5acd99d08e74 100644
> --- a/arch/riscv/include/asm/fixmap.h
> +++ b/arch/riscv/include/asm/fixmap.h
> @@ -43,7 +43,7 @@ enum fixed_addresses {
> __end_of_fixed_addresses
> };
>
> -#define FIXMAP_PAGE_IO PAGE_KERNEL
> +#define FIXMAP_PAGE_IO PAGE_IOREMAP
>
> #define __early_set_fixmap __set_fixmap
>
> diff --git a/arch/riscv/include/asm/pgtable-64.h b/arch/riscv/include/asm/pgtable-64.h
> index 228261aa9628..0b53ea67e91a 100644
> --- a/arch/riscv/include/asm/pgtable-64.h
> +++ b/arch/riscv/include/asm/pgtable-64.h
> @@ -61,12 +61,14 @@ static inline void pud_clear(pud_t *pudp)
>
> static inline pmd_t *pud_pgtable(pud_t pud)
> {
> - return (pmd_t *)pfn_to_virt(pud_val(pud) >> _PAGE_PFN_SHIFT);
> + return (pmd_t *)pfn_to_virt((pud_val(pud) & _PAGE_CHG_MASK)
> + >> _PAGE_PFN_SHIFT);
> }
>
> static inline struct page *pud_page(pud_t pud)
> {
> - return pfn_to_page(pud_val(pud) >> _PAGE_PFN_SHIFT);
> + return pfn_to_page((pud_val(pud) & _PAGE_CHG_MASK)
> + >> _PAGE_PFN_SHIFT);
> }
>
> static inline pmd_t pfn_pmd(unsigned long pfn, pgprot_t prot)
> @@ -76,7 +78,7 @@ static inline pmd_t pfn_pmd(unsigned long pfn, pgprot_t prot)
>
> static inline unsigned long _pmd_pfn(pmd_t pmd)
> {
> - return pmd_val(pmd) >> _PAGE_PFN_SHIFT;
> + return (pmd_val(pmd) & _PAGE_CHG_MASK) >> _PAGE_PFN_SHIFT;
> }
>
> #define mk_pmd(page, prot) pfn_pmd(page_to_pfn(page), prot)
> diff --git a/arch/riscv/include/asm/pgtable-bits.h b/arch/riscv/include/asm/pgtable-bits.h
> index 2ee413912926..041fe4fdbafa 100644
> --- a/arch/riscv/include/asm/pgtable-bits.h
> +++ b/arch/riscv/include/asm/pgtable-bits.h
> @@ -7,7 +7,7 @@
> #define _ASM_RISCV_PGTABLE_BITS_H
>
> /*
> - * PTE format:
> + * rv32 PTE format:
> * | XLEN-1 10 | 9 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0
> * PFN reserved for SW D A G U X W R V
> */
> @@ -24,6 +24,47 @@
> #define _PAGE_DIRTY (1 << 7) /* Set by hardware on any write */
> #define _PAGE_SOFT (1 << 8) /* Reserved for software */
>
> +#ifndef __ASSEMBLY__
> +#ifdef CONFIG_64BIT
> +/*
> + * rv64 PTE format:
> + * | 63 | 62 61 | 60 54 | 53 10 | 9 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0
> + * N MT RSV PFN reserved for SW D A G U X W R V
> + * [62:61] Memory Type definitions:
> + * 00 - PMA Normal Cacheable, No change to implied PMA memory type
> + * 01 - NC Non-cacheable, idempotent, weakly-ordered Main Memory
> + * 10 - IO Non-cacheable, non-idempotent, strongly-ordered I/O memory
> + * 11 - Rsvd Reserved for future standard use
> + */
> +#define _PAGE_MT_MASK ((u64)0x3 << 61)
> +#define _PAGE_MT_PMA ((u64)0x0 << 61)
> +#define _PAGE_MT_NC ((u64)0x1 << 61)
> +#define _PAGE_MT_IO ((u64)0x2 << 61)
> +
> +enum {
> + MT_PMA,
> + MT_NC,
> + MT_IO,
> + MT_MAX
> +};
> +
> +extern struct __riscv_svpbmt_struct {
> + unsigned long mask;
> + unsigned long mt[MT_MAX];
> +} __riscv_svpbmt;
> +
> +#define _PAGE_DMA_MASK __riscv_svpbmt.mask
> +#define _PAGE_DMA_PMA __riscv_svpbmt.mt[MT_PMA]
> +#define _PAGE_DMA_NC __riscv_svpbmt.mt[MT_NC]
> +#define _PAGE_DMA_IO __riscv_svpbmt.mt[MT_IO]
> +#else
> +#define _PAGE_DMA_MASK 0
> +#define _PAGE_DMA_PMA 0
> +#define _PAGE_DMA_NC 0
> +#define _PAGE_DMA_IO 0
> +#endif /* CONFIG_64BIT */
> +#endif /* __ASSEMBLY__ */
> +
> #define _PAGE_SPECIAL _PAGE_SOFT
> #define _PAGE_TABLE _PAGE_PRESENT
>
> @@ -38,7 +79,8 @@
> /* Set of bits to preserve across pte_modify() */
> #define _PAGE_CHG_MASK (~(unsigned long)(_PAGE_PRESENT | _PAGE_READ | \
> _PAGE_WRITE | _PAGE_EXEC | \
> - _PAGE_USER | _PAGE_GLOBAL))
> + _PAGE_USER | _PAGE_GLOBAL | \
> + _PAGE_DMA_MASK))
> /*
> * when all of R/W/X are zero, the PTE is a pointer to the next level
> * of the page table; otherwise, it is a leaf PTE.
> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> index 39b550310ec6..d07ba586c866 100644
> --- a/arch/riscv/include/asm/pgtable.h
> +++ b/arch/riscv/include/asm/pgtable.h
> @@ -136,7 +136,8 @@
> | _PAGE_PRESENT \
> | _PAGE_ACCESSED \
> | _PAGE_DIRTY \
> - | _PAGE_GLOBAL)
> + | _PAGE_GLOBAL \
> + | _PAGE_DMA_PMA)
>
> #define PAGE_KERNEL __pgprot(_PAGE_KERNEL)
> #define PAGE_KERNEL_READ __pgprot(_PAGE_KERNEL & ~_PAGE_WRITE)
> @@ -146,11 +147,9 @@
>
> #define PAGE_TABLE __pgprot(_PAGE_TABLE)
>
> -/*
> - * The RISC-V ISA doesn't yet specify how to query or modify PMAs, so we can't
> - * change the properties of memory regions.
> - */
> -#define _PAGE_IOREMAP _PAGE_KERNEL
> +#define _PAGE_IOREMAP ((_PAGE_KERNEL & ~_PAGE_DMA_MASK) | _PAGE_DMA_IO)
> +
> +#define PAGE_IOREMAP __pgprot(_PAGE_IOREMAP)
>
> extern pgd_t swapper_pg_dir[];
>
> @@ -230,12 +229,12 @@ static inline unsigned long _pgd_pfn(pgd_t pgd)
>
> static inline struct page *pmd_page(pmd_t pmd)
> {
> - return pfn_to_page(pmd_val(pmd) >> _PAGE_PFN_SHIFT);
> + return pfn_to_page((pmd_val(pmd) & _PAGE_CHG_MASK) >> _PAGE_PFN_SHIFT);
> }
>
> static inline unsigned long pmd_page_vaddr(pmd_t pmd)
> {
> - return (unsigned long)pfn_to_virt(pmd_val(pmd) >> _PAGE_PFN_SHIFT);
> + return (unsigned long)pfn_to_virt((pmd_val(pmd) & _PAGE_CHG_MASK) >> _PAGE_PFN_SHIFT);
> }
>
> static inline pte_t pmd_pte(pmd_t pmd)
> @@ -251,7 +250,7 @@ static inline pte_t pud_pte(pud_t pud)
> /* Yields the page frame number (PFN) of a page table entry */
> static inline unsigned long pte_pfn(pte_t pte)
> {
> - return (pte_val(pte) >> _PAGE_PFN_SHIFT);
> + return ((pte_val(pte) & _PAGE_CHG_MASK) >> _PAGE_PFN_SHIFT);
> }
>
> #define pte_page(x) pfn_to_page(pte_pfn(x))
> @@ -490,6 +489,28 @@ static inline int ptep_clear_flush_young(struct vm_area_struct *vma,
> return ptep_test_and_clear_young(vma, address, ptep);
> }
>
> +#define pgprot_noncached pgprot_noncached
> +static inline pgprot_t pgprot_noncached(pgprot_t _prot)
> +{
> + unsigned long prot = pgprot_val(_prot);
> +
> + prot &= ~_PAGE_DMA_MASK;
> + prot |= _PAGE_DMA_IO;
> +
> + return __pgprot(prot);
> +}
> +
> +#define pgprot_writecombine pgprot_writecombine
> +static inline pgprot_t pgprot_writecombine(pgprot_t _prot)
> +{
> + unsigned long prot = pgprot_val(_prot);
> +
> + prot &= ~_PAGE_DMA_MASK;
> + prot |= _PAGE_DMA_NC;
> +
> + return __pgprot(prot);
> +}
> +
> /*
> * THP functions
> */
> diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
> index 021ed64ee608..92676156cbf6 100644
> --- a/arch/riscv/include/asm/processor.h
> +++ b/arch/riscv/include/asm/processor.h
> @@ -70,6 +70,7 @@ struct device_node;
> int riscv_of_processor_hartid(struct device_node *node);
> int riscv_of_parent_hartid(struct device_node *node);
>
> +extern void riscv_svpbmt(void);
You can drop this change.
> extern void riscv_fill_hwcap(void);
> extern int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src);
>
> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> index d959d207a40d..4a2211c2c464 100644
> --- a/arch/riscv/kernel/cpufeature.c
> +++ b/arch/riscv/kernel/cpufeature.c
> @@ -8,6 +8,7 @@
>
> #include <linux/bitmap.h>
> #include <linux/of.h>
> +#include <linux/pgtable.h>
> #include <asm/processor.h>
> #include <asm/hwcap.h>
> #include <asm/smp.h>
> @@ -59,6 +60,28 @@ bool __riscv_isa_extension_available(const unsigned long *isa_bitmap, int bit)
> }
> EXPORT_SYMBOL_GPL(__riscv_isa_extension_available);
>
> +void __init riscv_svpbmt(void)
Make this static function and call it from riscv_fill_hwcap().
> +{
> +#ifdef CONFIG_64BIT
> + struct device_node *node;
> + const char *str;
> +
> + for_each_of_cpu_node(node) {
> + if (of_property_read_string(node, "mmu-type", &str)) {
> + continue;
> + }
> +
> + if (!strncmp(str + 11, "svpbmt", 6)) {
> + __riscv_svpbmt.mask = _PAGE_MT_MASK;
> + __riscv_svpbmt.mt[MT_PMA] = _PAGE_MT_PMA;
> + __riscv_svpbmt.mt[MT_NC] = _PAGE_MT_NC;
> + __riscv_svpbmt.mt[MT_IO] = _PAGE_MT_IO;
> + break;
> + }
I don't agree with this loop.
The __riscv_svpbmt should be updated only when all CPU nodes
have "svpmbt" in the "mmu-type" DT property.
> + }
> +#endif
> +}
> +
> void __init riscv_fill_hwcap(void)
> {
> struct device_node *node;
> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
> index 120b2f6f71bc..e7457113b45e 100644
> --- a/arch/riscv/kernel/setup.c
> +++ b/arch/riscv/kernel/setup.c
> @@ -294,6 +294,8 @@ void __init setup_arch(char **cmdline_p)
> setup_smp();
> #endif
>
> + riscv_svpbmt();
> +
You can drop this change based on above comment.
> riscv_fill_hwcap();
> }
>
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 7cb4f391d106..43b2e11fd3e0 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -905,3 +905,8 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
> return vmemmap_populate_basepages(start, end, node, NULL);
> }
> #endif
> +
> +#ifdef CONFIG_64BIT
> +struct __riscv_svpbmt_struct __riscv_svpbmt __ro_after_init;
> +EXPORT_SYMBOL(__riscv_svpbmt);
> +#endif
> --
> 2.25.1
>
Appending "svpmb" suffix to "mmu-type" breaks print_mmu()
in arch/riscv/kernel/cpu.c. Please update that as well.
We will also need couple of Tested-by for existing boards.
Regards,
Anup
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