Re: [PATCH] riscv: Add RISC-V svpbmt extension
From: Guo Ren
Date: Thu Sep 23 2021 - 07:53:27 EST
On Thu, Sep 23, 2021 at 5:13 PM Anup Patel <anup@xxxxxxxxxxxxxx> wrote:
>
> On Thu, Sep 23, 2021 at 12:57 PM <guoren@xxxxxxxxxx> wrote:
> >
> > From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
> >
> > 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@xxxxxxxxxxxxxxxxx>
> > Cc: Liu Shaohua <liush@xxxxxxxxxxxxxxxxx>
> > Cc: Wei Fu <wefu@xxxxxxxxxx>
> > Cc: Palmer Dabbelt <palmerdabbelt@xxxxxxxxxx>
> > Cc: Christoph Hellwig <hch@xxxxxx>
> > Cc: Anup Patel <anup.patel@xxxxxxx>
> > Cc: Arnd Bergmann <arnd@xxxxxxxx>
> > Cc: Atish Patra <atish.patra@xxxxxxx>
> > Cc: Drew Fustini <drew@xxxxxxxxxxxxxxx>
> > Cc: Wei Fu <wefu@xxxxxxxxxx>
> > Cc: Wei Wu <lazyparser@xxxxxxxxx>
> > Cc: Chen-Yu Tsai <wens@xxxxxxxx>
> > Cc: Maxime Ripard <maxime@xxxxxxxxxx>
> > Cc: Daniel Lustig <dlustig@xxxxxxxxxx>
> > Cc: Greg Favor <gfavor@xxxxxxxxxxxxxxxx>
> > Cc: Andrea Mondelli <andrea.mondelli@xxxxxxxxxx>
> > Cc: Jonathan Behrens <behrensj@xxxxxxx>
> > Cc: Xinhaoqu (Freddie) <xinhaoqu@xxxxxxxxxx>
> > Cc: Bill Huffman <huffman@xxxxxxxxxxx>
> > Cc: Nick Kossifidis <mick@xxxxxxxxxxxx>
> > Cc: Allen Baum <allen.baum@xxxxxxxxxxxxxxxxx>
> > Cc: Josh Scheid <jscheid@xxxxxxxxxxxxxxxx>
> > Cc: Richard Trauben <rtrauben@xxxxxxxxx>
> > ---
> > .../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 ..."
Okay
>
> Also, DT bindings change is generally a separate patch so better to make
> a separate patch for this.
Okay
>
> >
> > 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().
Okay
>
> > +{
> > +#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.
Okay
>
> > + }
> > +#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.
Okay
>
> We will also need couple of Tested-by for existing boards.
>
> Regards,
> Anup
--
Best Regards
Guo Ren
ML: https://lore.kernel.org/linux-csky/