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Message-ID: <CAAhSdy1LF4Km8ax00NdT3sUYqJRaW-nwXFCpviahpcDj2LLUAw@mail.gmail.com>
Date: Wed, 1 Dec 2021 11:48:44 +0530
From: Anup Patel <anup@...infault.org>
To: Wei Fu <wefu@...hat.com>
Cc: Jisheng Zhang <jszhang@...nel.org>,
Anup Patel <anup.patel@....com>,
atish patra <atishp04@...il.com>,
Palmer Dabbelt <palmer@...belt.com>,
Guo Ren <guoren@...nel.org>,
Christoph Müllner <christoph.muellner@...ll.eu>,
Philipp Tomsich <philipp.tomsich@...ll.eu>,
Christoph Hellwig <hch@....de>,
Liu Shaohua <liush@...winnertech.com>,
Wei Wu (吴伟) <lazyparser@...il.com>,
Drew Fustini <drew@...gleboard.org>,
linux-riscv <linux-riscv@...ts.infradead.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
taiten.peng@...onical.com,
Aniket Ponkshe <aniket.ponkshe@...onical.com>,
Heinrich Schuchardt <heinrich.schuchardt@...onical.com>,
Gordan Markus <gordan.markus@...onical.com>,
Guo Ren <guoren@...ux.alibaba.com>,
Arnd Bergmann <arnd@...db.de>, Chen-Yu Tsai <wens@...e.org>,
Maxime Ripard <maxime@...no.tech>,
Daniel Lustig <dlustig@...dia.com>,
Greg Favor <gfavor@...tanamicro.com>,
Andrea Mondelli <andrea.mondelli@...wei.com>,
Jonathan Behrens <behrensj@....edu>,
Xinhaoqu <xinhaoqu@...wei.com>,
Bill Huffman <huffman@...ence.com>,
Nick Kossifidis <mick@....forth.gr>,
Allen Baum <allen.baum@...erantotech.com>,
Josh Scheid <jscheid@...tanamicro.com>,
Richard Trauben <rtrauben@...il.com>
Subject: Re: [PATCH V4 2/2] riscv: add RISC-V Svpbmt extension supports
On Wed, Dec 1, 2021 at 10:35 AM Wei Fu <wefu@...hat.com> wrote:
>
> Hi, Jisheng Zhang,
>
> On Mon, Nov 29, 2021 at 9:44 PM Jisheng Zhang <jszhang@...nel.org> wrote:
> >
> > On Mon, 29 Nov 2021 09:40:07 +0800
> > wefu@...hat.com wrote:
> >
> > > From: Wei Fu <wefu@...hat.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. And the whole modification is
> > > limited in the arch/riscv/* and using a global variable
> > > (__svpbmt) as _PAGE_MASK/IO/NOCACHE for pgprot_noncached
> > > (&writecombine) in pgtable.h. We also add _PAGE_CHG_MASK to filter
> > > PFN than before.
> > >
> > > Enable it in devicetree - (Add "riscv,svpbmt" in the mmu of cpu node)
> > > - mmu:
> > > riscv,svpmbt
> > >
> > > Signed-off-by: Wei Fu <wefu@...hat.com>
> > > Co-developed-by: Liu Shaohua <liush@...winnertech.com>
> > > Signed-off-by: Liu Shaohua <liush@...winnertech.com>
> > > Co-developed-by: Guo Ren <guoren@...nel.org>
> > > Signed-off-by: Guo Ren <guoren@...nel.org>
> > > Cc: Palmer Dabbelt <palmerdabbelt@...gle.com>
> > > Cc: Christoph Hellwig <hch@....de>
> > > Cc: Anup Patel <anup.patel@....com>
> > > Cc: Arnd Bergmann <arnd@...db.de>
> > > Cc: Atish Patra <atish.patra@....com>
> > > Cc: Drew Fustini <drew@...gleboard.org>
> > > Cc: Wei Fu <wefu@...hat.com>
> > > Cc: Wei Wu <lazyparser@...il.com>
> > > Cc: Chen-Yu Tsai <wens@...e.org>
> > > Cc: Maxime Ripard <maxime@...no.tech>
> > > Cc: Daniel Lustig <dlustig@...dia.com>
> > > Cc: Greg Favor <gfavor@...tanamicro.com>
> > > Cc: Andrea Mondelli <andrea.mondelli@...wei.com>
> > > Cc: Jonathan Behrens <behrensj@....edu>
> > > Cc: Xinhaoqu (Freddie) <xinhaoqu@...wei.com>
> > > Cc: Bill Huffman <huffman@...ence.com>
> > > Cc: Nick Kossifidis <mick@....forth.gr>
> > > Cc: Allen Baum <allen.baum@...erantotech.com>
> > > Cc: Josh Scheid <jscheid@...tanamicro.com>
> > > Cc: Richard Trauben <rtrauben@...il.com>
> > > ---
> > > arch/riscv/include/asm/fixmap.h | 2 +-
> > > arch/riscv/include/asm/pgtable-64.h | 21 ++++++++++++---
> > > arch/riscv/include/asm/pgtable-bits.h | 39 +++++++++++++++++++++++++--
> > > arch/riscv/include/asm/pgtable.h | 39 ++++++++++++++++++++-------
> > > arch/riscv/kernel/cpufeature.c | 35 ++++++++++++++++++++++++
> > > arch/riscv/mm/init.c | 5 ++++
> > > 6 files changed, 126 insertions(+), 15 deletions(-)
> > >
> > > 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..16d251282b1d 100644
> > > --- a/arch/riscv/include/asm/pgtable-64.h
> > > +++ b/arch/riscv/include/asm/pgtable-64.h
> > > @@ -59,14 +59,29 @@ static inline void pud_clear(pud_t *pudp)
> > > set_pud(pudp, __pud(0));
> > > }
> > >
> > > +static inline unsigned long _chg_of_pmd(pmd_t pmd)
> > > +{
> > > + return (pmd_val(pmd) & _PAGE_CHG_MASK);
> > > +}
> > > +
> > > +static inline unsigned long _chg_of_pud(pud_t pud)
> > > +{
> > > + return (pud_val(pud) & _PAGE_CHG_MASK);
> > > +}
> > > +
> > > +static inline unsigned long _chg_of_pte(pte_t pte)
> > > +{
> > > + return (pte_val(pte) & _PAGE_CHG_MASK);
> > > +}
> > > +
> > > 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(_chg_of_pud(pud) >> _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(_chg_of_pud(pud) >> _PAGE_PFN_SHIFT);
> > > }
> > >
> > > static inline pmd_t pfn_pmd(unsigned long pfn, pgprot_t prot)
> > > @@ -76,7 +91,7 @@ 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 _chg_of_pmd(pmd) >> _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..e5b0fce4ddc5 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 +24,40 @@
> > > #define _PAGE_DIRTY (1 << 7) /* Set by hardware on any write */
> > > #define _PAGE_SOFT (1 << 8) /* Reserved for software */
> > >
> > > +#if !defined(__ASSEMBLY__) && defined(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 _SVPBMT_PMA 0UL
> > > +#define _SVPBMT_NC (1UL << 61)
> > > +#define _SVPBMT_IO (1UL << 62)
> > > +#define _SVPBMT_MASK (_SVPBMT_NC | _SVPBMT_IO)
> > > +
> > > +extern struct __svpbmt_struct {
> > > + unsigned long mask;
> > > + unsigned long pma;
> > > + unsigned long nocache;
> > > + unsigned long io;
> > > +} __svpbmt __cacheline_aligned;
> > > +
> > > +#define _PAGE_MASK __svpbmt.mask
> > > +#define _PAGE_PMA __svpbmt.pma
> > > +#define _PAGE_NOCACHE __svpbmt.nocache
> > > +#define _PAGE_IO __svpbmt.io
> > > +#else
> > > +#define _PAGE_MASK 0
> > > +#define _PAGE_PMA 0
> > > +#define _PAGE_NOCACHE 0
> > > +#define _PAGE_IO 0
> > > +#endif /* !__ASSEMBLY__ && CONFIG_64BIT */
> > > +
> > > #define _PAGE_SPECIAL _PAGE_SOFT
> > > #define _PAGE_TABLE _PAGE_PRESENT
> > >
> > > @@ -38,7 +72,8 @@
> > > /* 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_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 bf204e7c1f74..0f7a6541015f 100644
> > > --- a/arch/riscv/include/asm/pgtable.h
> > > +++ b/arch/riscv/include/asm/pgtable.h
> > > @@ -138,7 +138,8 @@
> > > | _PAGE_PRESENT \
> > > | _PAGE_ACCESSED \
> > > | _PAGE_DIRTY \
> > > - | _PAGE_GLOBAL)
> > > + | _PAGE_GLOBAL \
> > > + | _PAGE_PMA)
> > >
> > > #define PAGE_KERNEL __pgprot(_PAGE_KERNEL)
> > > #define PAGE_KERNEL_READ __pgprot(_PAGE_KERNEL & ~_PAGE_WRITE)
> > > @@ -148,11 +149,9 @@
> > >
> > > #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_MASK) | _PAGE_IO)
> > > +
> > > +#define PAGE_IOREMAP __pgprot(_PAGE_IOREMAP)
> > >
> > > extern pgd_t swapper_pg_dir[];
> > >
> > > @@ -232,12 +231,12 @@ 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(_chg_of_pmd(pmd) >> _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(_chg_of_pmd(pmd) >> _PAGE_PFN_SHIFT);
> > > }
> > >
> > > static inline pte_t pmd_pte(pmd_t pmd)
> > > @@ -253,7 +252,7 @@ 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 (_chg_of_pte(pte) >> _PAGE_PFN_SHIFT);
> > > }
> > >
> > > #define pte_page(x) pfn_to_page(pte_pfn(x))
> > > @@ -492,6 +491,28 @@ 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_MASK;
> > > + prot |= _PAGE_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_MASK;
> > > + prot |= _PAGE_NOCACHE;
> > > +
> > > + return __pgprot(prot);
> > > +}
> > > +
> > > /*
> > > * THP functions
> > > */
> > > diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> > > index d959d207a40d..fa7480cb8b87 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 +60,38 @@ bool __riscv_isa_extension_available(const unsigned long *isa_bitmap, int bit)
> > > }
> > > EXPORT_SYMBOL_GPL(__riscv_isa_extension_available);
> > >
> > > +static void __init mmu_supports_svpbmt(void)
> > > +{
> > > +#if defined(CONFIG_MMU) && defined(CONFIG_64BIT)
> >
> > IIRC, Christoph suggested a CONFIG_RISCV_SVPBMT when reviewing v3. What
> > about that idea?
>
> Yes, sorry for missing it, yes, I think we can have something like this
>
> config ARCH_HAS_RISCV_SVPBMT
> bool
> default n
>
> any platform which needs this support, can just
>
> select ARCH_HAS_RISCV_SVPBMT
>
> and which is the best name? ARCH_HAS_RISCV_SVPBMT or just ARCH_HAS_SVPBMT ?
>
> >
> > > + 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 + 6, "none", 4))
> > > + continue;
> > > +
> > > + if (of_property_read_string(node, "mmu", &str))
> > > + continue;
> > > +
> > > + if (strncmp(str + 6, "svpmbt", 6))
> > > + continue;
> > > + }
> > > +
> > > + __svpbmt.pma = _SVPBMT_PMA;
> > > + __svpbmt.nocache = _SVPBMT_NC;
> > > + __svpbmt.io = _SVPBMT_IO;
> > > + __svpbmt.mask = _SVPBMT_MASK;
> > > +#endif
> > > +}
> > > +
> > > +static void __init mmu_supports(void)
> >
> > can we remove this function currently? Instead, directly call
> > mmu_supports_svpbmt()?
> >
> > > +{
> > > + mmu_supports_svpbmt();
> > > +}
> > > +
> > > void __init riscv_fill_hwcap(void)
> > > {
> > > struct device_node *node;
> > > @@ -67,6 +100,8 @@ void __init riscv_fill_hwcap(void)
> > > size_t i, j, isa_len;
> > > static unsigned long isa2hwcap[256] = {0};
> > >
> > > + mmu_supports();
> > > +
> > > isa2hwcap['i'] = isa2hwcap['I'] = COMPAT_HWCAP_ISA_I;
> > > isa2hwcap['m'] = isa2hwcap['M'] = COMPAT_HWCAP_ISA_M;
> > > isa2hwcap['a'] = isa2hwcap['A'] = COMPAT_HWCAP_ISA_A;
> > > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> > > index 24b2b8044602..e4e658165ee1 100644
> > > --- a/arch/riscv/mm/init.c
> > > +++ b/arch/riscv/mm/init.c
> > > @@ -854,3 +854,8 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
> > > return vmemmap_populate_basepages(start, end, node, NULL);
> > > }
> > > #endif
> > > +
> > > +#if defined(CONFIG_64BIT)
> > > +struct __svpbmt_struct __svpbmt __ro_after_init;
> >
> > Added the structure for all RV64 including NOMMU case and those platforms
> > which doen't want SVPBMT at all, I believe Christoph's CONFIG_RISCV_SVPBMT
> > suggestion can solve this problem.
>
> see ARCH_HAS_RISCV_SVPBMT above . :-)
This config option will not align with the goal of having a unified
kernel image which works on HW with/without Svpmbt.
Better to explore code patching approaches which have zero
overhead.
Regards,
Anup
>
> >
> > > +EXPORT_SYMBOL(__svpbmt);
> > > +#endif
> >
>
>
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