Re: [PATCH v6 14/14] riscv: add memory-type errata for T-Head
From: Atish Patra
Date: Fri Feb 11 2022 - 19:28:07 EST
On Fri, Feb 11, 2022 at 1:25 AM Heiko Stübner <heiko@xxxxxxxxx> wrote:
>
> Hi Atish,
>
> Am Freitag, 11. Februar 2022, 01:12:55 CET schrieb Atish Patra:
> > On Wed, Feb 9, 2022 at 4:41 AM Heiko Stuebner <heiko@xxxxxxxxx> wrote:
> > >
> > > Some current cpus based on T-Head cores implement memory-types
> > > way different than described in the svpbmt spec even going
> > > so far as using PTE bits marked as reserved.
> > >
> > > Add the T-Head vendor-id and necessary errata code to
> > > replace the affected instructions.
> > >
> > > Signed-off-by: Heiko Stuebner <heiko@xxxxxxxxx>
> > > ---
> > > arch/riscv/Kconfig.erratas | 19 ++++++
> > > arch/riscv/errata/Makefile | 1 +
> > > arch/riscv/errata/sifive/errata.c | 7 ++-
> > > arch/riscv/errata/thead/Makefile | 1 +
> > > arch/riscv/errata/thead/errata.c | 85 ++++++++++++++++++++++++++
> > > arch/riscv/include/asm/alternative.h | 5 ++
> > > arch/riscv/include/asm/errata_list.h | 47 ++++++++++++--
> > > arch/riscv/include/asm/pgtable-64.h | 18 +++++-
> > > arch/riscv/include/asm/pgtable.h | 18 +++++-
> > > arch/riscv/include/asm/vendorid_list.h | 1 +
> > > arch/riscv/kernel/alternative.c | 14 +++++
> > > arch/riscv/kernel/cpufeature.c | 2 +
> > > arch/riscv/mm/init.c | 1 +
> > > 13 files changed, 210 insertions(+), 9 deletions(-)
> > > create mode 100644 arch/riscv/errata/thead/Makefile
> > > create mode 100644 arch/riscv/errata/thead/errata.c
> > >
> > > diff --git a/arch/riscv/Kconfig.erratas b/arch/riscv/Kconfig.erratas
> > > index d18be8ff0245..380ec039c3dc 100644
> > > --- a/arch/riscv/Kconfig.erratas
> > > +++ b/arch/riscv/Kconfig.erratas
> > > @@ -31,4 +31,23 @@ config ERRATA_SIFIVE_CIP_1200
> > >
> > > If you don't know what to do here, say "Y".
> > >
> > > +config ERRATA_THEAD
> > > + bool "T-HEAD errata"
> > > + help
> > > + All T-HEAD errata Kconfig depend on this Kconfig. Disabling
> > > + this Kconfig will disable all T-HEAD errata. Please say "Y"
> > > + here if your platform uses T-HEAD CPU cores.
> > > +
> > > + If you don't know what to do here, say "Y".
> > > +
> > > +config ERRATA_THEAD_PBMT
> > > + bool "Apply T-Head memory type errata"
> > > + depends on ERRATA_THEAD && 64BIT
> > > + default y
> > > + help
> > > + This will apply the memory type errata to handle the non-standard
> > > + memory type bits in page-table-entries on T-Head SoCs.
> > > +
> > > + If you don't know what to do here, say "Y".
> > > +
> > > endmenu
> > > diff --git a/arch/riscv/errata/Makefile b/arch/riscv/errata/Makefile
> > > index 0ca1c5281a2d..a1055965fbee 100644
> > > --- a/arch/riscv/errata/Makefile
> > > +++ b/arch/riscv/errata/Makefile
> > > @@ -1 +1,2 @@
> > > obj-$(CONFIG_ERRATA_SIFIVE) += sifive/
> > > +obj-$(CONFIG_ERRATA_THEAD) += thead/
> > > diff --git a/arch/riscv/errata/sifive/errata.c b/arch/riscv/errata/sifive/errata.c
> > > index 4fe03ac41fd7..f933d6cdf304 100644
> > > --- a/arch/riscv/errata/sifive/errata.c
> > > +++ b/arch/riscv/errata/sifive/errata.c
> > > @@ -84,10 +84,15 @@ void __init sifive_errata_patch_func(struct alt_entry *begin, struct alt_entry *
> > > unsigned int stage)
> > > {
> > > struct alt_entry *alt;
> > > - u32 cpu_req_errata = sifive_errata_probe(archid, impid);
> > > + u32 cpu_req_errata;
> > > u32 cpu_apply_errata = 0;
> > > u32 tmp;
> > >
> > > + if (stage == RISCV_ALTERNATIVES_EARLY_BOOT)
> > > + return;
> > > +
> > > + cpu_req_errata = sifive_errata_probe(archid, impid);
> > > +
> > > for (alt = begin; alt < end; alt++) {
> > > if (alt->vendor_id != SIFIVE_VENDOR_ID)
> > > continue;
> > > diff --git a/arch/riscv/errata/thead/Makefile b/arch/riscv/errata/thead/Makefile
> > > new file mode 100644
> > > index 000000000000..2d644e19caef
> > > --- /dev/null
> > > +++ b/arch/riscv/errata/thead/Makefile
> > > @@ -0,0 +1 @@
> > > +obj-y += errata.o
> > > diff --git a/arch/riscv/errata/thead/errata.c b/arch/riscv/errata/thead/errata.c
> > > new file mode 100644
> > > index 000000000000..fd8e0538a3f0
> > > --- /dev/null
> > > +++ b/arch/riscv/errata/thead/errata.c
> > > @@ -0,0 +1,85 @@
> > > +// SPDX-License-Identifier: GPL-2.0-only
> > > +/*
> > > + * Copyright (C) 2021 Heiko Stuebner <heiko@xxxxxxxxx>
> > > + */
> > > +
> > > +#include <linux/bug.h>
> > > +#include <linux/kernel.h>
> > > +#include <linux/module.h>
> > > +#include <linux/string.h>
> > > +#include <linux/uaccess.h>
> > > +#include <asm/alternative.h>
> > > +#include <asm/cacheflush.h>
> > > +#include <asm/errata_list.h>
> > > +#include <asm/patch.h>
> > > +#include <asm/vendorid_list.h>
> > > +
> > > +struct errata_info {
> > > + char name[ERRATA_STRING_LENGTH_MAX];
> > > + bool (*check_func)(unsigned long arch_id, unsigned long impid);
> > > + unsigned int stage;
> > > +};
> > > +
> > > +static bool errata_mt_check_func(unsigned long arch_id, unsigned long impid)
> > > +{
> > > + if (arch_id != 0 || impid != 0)
> > > + return false;
> > > + return true;
> > > +}
> > > +
> > > +static const struct errata_info errata_list[ERRATA_THEAD_NUMBER] = {
> > > + {
> > > + .name = "memory-types",
> > > + .stage = RISCV_ALTERNATIVES_EARLY_BOOT,
> > > + .check_func = errata_mt_check_func
> > > + },
> > > +};
> > > +
> > > +static u32 thead_errata_probe(unsigned int stage, unsigned long archid, unsigned long impid)
> > > +{
> > > + const struct errata_info *info;
> > > + u32 cpu_req_errata = 0;
> > > + int idx;
> > > +
> > > + for (idx = 0; idx < ERRATA_THEAD_NUMBER; idx++) {
> > > + info = &errata_list[idx];
> > > +
> > > + if ((stage == RISCV_ALTERNATIVES_MODULE ||
> > > + info->stage == stage) && info->check_func(archid, impid))
> > > + cpu_req_errata |= (1U << idx);
> > > + }
> > > +
> > > + return cpu_req_errata;
> > > +}
> > > +
> > > +void __init_or_module thead_errata_patch_func(struct alt_entry *begin, struct alt_entry *end,
> > > + unsigned long archid, unsigned long impid,
> > > + unsigned int stage)
> > > +{
> > > + struct alt_entry *alt;
> > > + u32 cpu_req_errata = thead_errata_probe(stage, archid, impid);
> > > + u32 cpu_apply_errata = 0;
> > > + u32 tmp;
> > > +
> > > + for (alt = begin; alt < end; alt++) {
> > > + if (alt->vendor_id != THEAD_VENDOR_ID)
> > > + continue;
> > > + if (alt->errata_id >= ERRATA_THEAD_NUMBER)
> > > + continue;
> > > +
> > > + tmp = (1U << alt->errata_id);
> > > + if (cpu_req_errata & tmp) {
> > > + /* On vm-alternatives, the mmu isn't running yet */
> > > + if (stage == RISCV_ALTERNATIVES_EARLY_BOOT)
> > > + memcpy((void *)__pa_symbol(alt->old_ptr),
> > > + (void *)__pa_symbol(alt->alt_ptr), alt->alt_len);
> > > + else
> > > + patch_text_nosync(alt->old_ptr, alt->alt_ptr, alt->alt_len);
> > > +
> > > + cpu_apply_errata |= tmp;
> > > + }
> > > + }
> > > +
> > > + if (stage == RISCV_ALTERNATIVES_EARLY_BOOT)
> > > + local_flush_icache_all();
> > > +}
> > > diff --git a/arch/riscv/include/asm/alternative.h b/arch/riscv/include/asm/alternative.h
> > > index cf3b22173834..d1154c91ab03 100644
> > > --- a/arch/riscv/include/asm/alternative.h
> > > +++ b/arch/riscv/include/asm/alternative.h
> > > @@ -19,8 +19,10 @@
> > >
> > > #define RISCV_ALTERNATIVES_BOOT 0 /* alternatives applied during regular boot */
> > > #define RISCV_ALTERNATIVES_MODULE 1 /* alternatives applied during module-init */
> > > +#define RISCV_ALTERNATIVES_EARLY_BOOT 2 /* alternatives applied before mmu start */
> > >
> >
> > But this stage invoked is used after RISCV_ALTERNATIVES_BOOT
>
> No it isn't.
>
> the "boot" alternative is applied right now directly before soc_early_init,
> while the "early-boot" alternative is already applied during setup_vm()
Yeah you are right. I got confused with the name and numbering.
> even before page-tables are set up.
>
> Right now the numbering doesn't reflect the order and just
> makes it distinct, but I guess we can adjust it to make that clear
> (move early_boot to the top)
>
>
> > > void __init apply_boot_alternatives(void);
> > > +void __init apply_early_boot_alternatives(void);
> > > void apply_module_alternatives(void *start, size_t length);
> > >
> > > struct alt_entry {
> > > @@ -39,6 +41,9 @@ struct errata_checkfunc_id {
> > > void sifive_errata_patch_func(struct alt_entry *begin, struct alt_entry *end,
> > > unsigned long archid, unsigned long impid,
> > > unsigned int stage);
> > > +void thead_errata_patch_func(struct alt_entry *begin, struct alt_entry *end,
> > > + unsigned long archid, unsigned long impid,
> > > + unsigned int stage);
> > >
> > > void riscv_cpufeature_patch_func(struct alt_entry *begin, struct alt_entry *end,
> > > unsigned int stage);
> > > diff --git a/arch/riscv/include/asm/errata_list.h b/arch/riscv/include/asm/errata_list.h
> > > index a4a9b0842922..4fac46b82c16 100644
> > > --- a/arch/riscv/include/asm/errata_list.h
> > > +++ b/arch/riscv/include/asm/errata_list.h
> > > @@ -14,6 +14,11 @@
> > > #define ERRATA_SIFIVE_NUMBER 2
> > > #endif
> > >
> > > +#ifdef CONFIG_ERRATA_THEAD
> > > +#define ERRATA_THEAD_PBMT 0
> > > +#define ERRATA_THEAD_NUMBER 1
> > > +#endif
> > > +
> > > #define CPUFEATURE_SVPBMT 0
> > > #define CPUFEATURE_NUMBER 1
> > >
> > > @@ -42,10 +47,44 @@ asm(ALTERNATIVE("sfence.vma %0", "sfence.vma", SIFIVE_VENDOR_ID, \
> > > * in the default case.
> > > */
> > > #define ALT_SVPBMT_SHIFT 61
> > > -#define ALT_SVPBMT(_val, prot) \
> > > -asm(ALTERNATIVE("li %0, 0\t\nnop", "li %0, %1\t\nslli %0,%0,%2", 0, \
> > > - CPUFEATURE_SVPBMT, CONFIG_64BIT) \
> > > - : "=r"(_val) : "I"(prot##_SVPBMT >> ALT_SVPBMT_SHIFT), "I"(ALT_SVPBMT_SHIFT))
> > > +#define ALT_THEAD_PBMT_SHIFT 59
> > > +#define ALT_SVPBMT(_val, prot) \
> > > +asm(ALTERNATIVE_2("li %0, 0\t\nnop", \
> > > + "li %0, %1\t\nslli %0,%0,%3", 0, CPUFEATURE_SVPBMT, CONFIG_64BIT, \
> > > + "li %0, %2\t\nslli %0,%0,%4", THEAD_VENDOR_ID, ERRATA_THEAD_PBMT, \
> > > + CONFIG_ERRATA_THEAD_PBMT) \
> > > + : "=r"(_val) : "I"(prot##_SVPBMT >> ALT_SVPBMT_SHIFT), \
> > > + "I"(prot##_THEAD >> ALT_THEAD_PBMT_SHIFT), \
> > > + "I"(ALT_SVPBMT_SHIFT), "I"(ALT_THEAD_PBMT_SHIFT))
> > > +
> > > +#ifdef CONFIG_ERRATA_THEAD_PBMT
> > > +/*
> > > + * IO/NOCACHE memory types are handled together with svpbmt,
> > > + * so on T-Head chips, check if no other memory type is set,
> > > + * and set the non-0 PMA type if applicable.
> > > + */
> > > +#define ALT_THEAD_PMA(_val) \
> > > +asm volatile(ALTERNATIVE( \
> > > + "nop\n\t" \
> > > + "nop\n\t" \
> > > + "nop\n\t" \
> > > + "nop\n\t" \
> > > + "nop\n\t" \
> > > + "nop\n\t" \
> > > + "nop", \
> > > + "li t3, %2\n\t" \
> > > + "slli t3, t3, %4\n\t" \
> > > + "and t3, %0, t3\n\t" \
> > > + "bne t3, zero, 2f\n\t" \
> > > + "li t3, %3\n\t" \
> > > + "slli t3, t3, %4\n\t" \
> > > + "or %0, %0, t3\n\t" \
> > > + "2:", THEAD_VENDOR_ID, ERRATA_THEAD_PBMT, CONFIG_ERRATA_THEAD_PBMT) \
> > > + : "+r"(_val) : "0"(_val), "I"(_PAGE_MTMASK_THEAD >> ALT_THEAD_PBMT_SHIFT), \
> > > + "I"(_PAGE_PMA_THEAD >> ALT_THEAD_PBMT_SHIFT), "I"(ALT_THEAD_PBMT_SHIFT))
> > > +#else
> > > +#define ALT_THEAD_PMA(_val)
> > > +#endif
> > >
> > > #endif /* __ASSEMBLY__ */
> > >
> > > diff --git a/arch/riscv/include/asm/pgtable-64.h b/arch/riscv/include/asm/pgtable-64.h
> > > index 07ba3416cb19..6d59e4695200 100644
> > > --- a/arch/riscv/include/asm/pgtable-64.h
> > > +++ b/arch/riscv/include/asm/pgtable-64.h
> > > @@ -69,6 +69,18 @@ typedef struct {
> > > #define _PAGE_IO_SVPBMT (1UL << 62)
> > > #define _PAGE_MTMASK_SVPBMT (_PAGE_NOCACHE_SVPBMT | _PAGE_IO_SVPBMT)
> > >
> > > +/*
> > > + * [63:59] T-Head Memory Type definitions:
> > > + *
> > > + * 00000 - NC Weakly-ordered, Non-cacheable, Non-bufferable, Non-shareable, Non-trustable
> > > + * 01110 - PMA Weakly-ordered, Cacheable, Bufferable, Shareable, Non-trustable
> > > + * 10000 - IO Strongly-ordered, Non-cacheable, Non-bufferable, Non-shareable, Non-trustable
> > > + */
> > > +#define _PAGE_PMA_THEAD ((1UL << 62) | (1UL << 61) | (1UL << 60))
> > > +#define _PAGE_NOCACHE_THEAD 0UL
> > > +#define _PAGE_IO_THEAD (1UL << 63)
> > > +#define _PAGE_MTMASK_THEAD (_PAGE_PMA_THEAD | _PAGE_IO_THEAD | (1UL << 59))
> > > +
> > > static inline u64 riscv_page_mtmask(void)
> > > {
> > > u64 val;
> > > @@ -167,7 +179,11 @@ static inline bool mm_pud_folded(struct mm_struct *mm)
> > >
> > > static inline pmd_t pfn_pmd(unsigned long pfn, pgprot_t prot)
> > > {
> > > - return __pmd((pfn << _PAGE_PFN_SHIFT) | pgprot_val(prot));
> > > + unsigned long prot_val = pgprot_val(prot);
> > > +
> > > + ALT_THEAD_PMA(prot_val);
> > > +
> > > + return __pmd((pfn << _PAGE_PFN_SHIFT) | prot_val);
> > > }
> > >
> > > static inline unsigned long _pmd_pfn(pmd_t pmd)
> > > diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> > > index b8abc75dfe01..3d0c4c144093 100644
> > > --- a/arch/riscv/include/asm/pgtable.h
> > > +++ b/arch/riscv/include/asm/pgtable.h
> > > @@ -245,7 +245,11 @@ static inline void pmd_clear(pmd_t *pmdp)
> > >
> > > static inline pgd_t pfn_pgd(unsigned long pfn, pgprot_t prot)
> > > {
> > > - return __pgd((pfn << _PAGE_PFN_SHIFT) | pgprot_val(prot));
> > > + unsigned long prot_val = pgprot_val(prot);
> > > +
> > > + ALT_THEAD_PMA(prot_val);
> > > +
> > > + return __pgd((pfn << _PAGE_PFN_SHIFT) | prot_val);
> > > }
> > >
> > > static inline unsigned long _pgd_pfn(pgd_t pgd)
> > > @@ -284,7 +288,11 @@ static inline unsigned long pte_pfn(pte_t pte)
> > > /* Constructs a page table entry */
> > > static inline pte_t pfn_pte(unsigned long pfn, pgprot_t prot)
> > > {
> > > - return __pte((pfn << _PAGE_PFN_SHIFT) | pgprot_val(prot));
> > > + unsigned long prot_val = pgprot_val(prot);
> > > +
> > > + ALT_THEAD_PMA(prot_val);
> > > +
> > > + return __pte((pfn << _PAGE_PFN_SHIFT) | prot_val);
> > > }
> > >
> > > #define mk_pte(page, prot) pfn_pte(page_to_pfn(page), prot)
> > > @@ -393,7 +401,11 @@ static inline int pmd_protnone(pmd_t pmd)
> > > /* Modify page protection bits */
> > > static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
> > > {
> > > - return __pte((pte_val(pte) & _PAGE_CHG_MASK) | pgprot_val(newprot));
> > > + unsigned long newprot_val = pgprot_val(newprot);
> > > +
> > > + ALT_THEAD_PMA(newprot_val);
> > > +
> > > + return __pte((pte_val(pte) & _PAGE_CHG_MASK) | newprot_val);
> > > }
> > >
> > > #define pgd_ERROR(e) \
> > > diff --git a/arch/riscv/include/asm/vendorid_list.h b/arch/riscv/include/asm/vendorid_list.h
> > > index 9d934215b3c8..cb89af3f0704 100644
> > > --- a/arch/riscv/include/asm/vendorid_list.h
> > > +++ b/arch/riscv/include/asm/vendorid_list.h
> > > @@ -6,5 +6,6 @@
> > > #define ASM_VENDOR_LIST_H
> > >
> > > #define SIFIVE_VENDOR_ID 0x489
> > > +#define THEAD_VENDOR_ID 0x5b7
> > >
> > > #endif
> > > diff --git a/arch/riscv/kernel/alternative.c b/arch/riscv/kernel/alternative.c
> > > index e6c9de9f9ba6..3f6ad91f524c 100644
> > > --- a/arch/riscv/kernel/alternative.c
> > > +++ b/arch/riscv/kernel/alternative.c
> > > @@ -48,6 +48,11 @@ static void __init init_alternative(void)
> > > case SIFIVE_VENDOR_ID:
> > > vendor_patch_func = sifive_errata_patch_func;
> > > break;
> > > +#endif
> > > +#ifdef CONFIG_ERRATA_THEAD
> > > + case THEAD_VENDOR_ID:
> > > + vendor_patch_func = thead_errata_patch_func;
> > > + break;
> > > #endif
> > > default:
> > > vendor_patch_func = NULL;
> > > @@ -85,6 +90,15 @@ void __init apply_boot_alternatives(void)
> > > RISCV_ALTERNATIVES_BOOT);
> > > }
> > >
> > > +void __init apply_early_boot_alternatives(void)
> > > +{
> > > + init_alternative();
> > > +
> > > + _apply_alternatives((struct alt_entry *)__alt_start,
> > > + (struct alt_entry *)__alt_end,
> > > + RISCV_ALTERNATIVES_EARLY_BOOT);
> > > +}
> > > +
> >
> > The name is a bit confusing as there is another "apply_boot_alternatives"
> > which was called earlier than "apply_early_boot_alternatives".
>
> I'm not that much attached to early-boot, so if you have other naming-
> suggestions we can of course change that.
>
Just a suggestion:
how about BEFORE_MMU and AFTER_MMU to indicate the purpose more clearly.
But I am okay with the current naming scheme as well.
> As explained above, the early-boot stage runs before page-table setup,
> so that things like the D1 can hook into it with their setting for the base
> page-type.
>
>
> Heiko
>
>
>
> > > #ifdef CONFIG_MODULES
> > > void apply_module_alternatives(void *start, size_t length)
> > > {
> > > diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> > > index 7bce66ee7ce7..ecc248e5dab7 100644
> > > --- a/arch/riscv/kernel/cpufeature.c
> > > +++ b/arch/riscv/kernel/cpufeature.c
> > > @@ -224,6 +224,8 @@ static bool cpufeature_svpbmt_check_func(unsigned int stage)
> > >
> > > #if defined(CONFIG_MMU) && defined(CONFIG_64BIT)
> > > switch (stage) {
> > > + case RISCV_ALTERNATIVES_EARLY_BOOT:
> > > + return false;
> > > case RISCV_ALTERNATIVES_BOOT:
> > > return cpufeature_svpbmt_check_fdt();
> > > default:
> > > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> > > index cf4d018b7d66..7216db5d6a2c 100644
> > > --- a/arch/riscv/mm/init.c
> > > +++ b/arch/riscv/mm/init.c
> > > @@ -819,6 +819,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
> > > BUG_ON((kernel_map.virt_addr + kernel_map.size) > ADDRESS_SPACE_END - SZ_4K);
> > > #endif
> > >
> > > + apply_early_boot_alternatives();
> > > pt_ops_set_early();
> > >
> > > /* Setup early PGD for fixmap */
> > > --
> > > 2.30.2
> > >
> > >
> > > _______________________________________________
> > > linux-riscv mailing list
> > > linux-riscv@xxxxxxxxxxxxxxxxxxx
> > > http://lists.infradead.org/mailman/listinfo/linux-riscv
> >
> >
> >
> > --
> > Regards,
> > Atish
> >
>
>
>
>
--
Regards,
Atish