[PATCH] riscv: Add RISC-V svpbmt extension

From: guoren
Date: Thu Sep 23 2021 - 03:27:32 EST

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

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);
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)
+{
+#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;
+ }
+ }
+#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();
+
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