[RFC PATCH v3 2/2] riscv: pgtable: Add "PBMT" extension supported

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From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>

"PBMT" - Page-Based Memory Types (see Link for detail), current it
has defined 3 memory types [62:61] in PTE:
 - WB 00 "Cacheable 'main memory'"
 - NC 01 "Noncacheable 'main memory'"
 - IO 11 "Non-cacheable non-idempotent 'I/O'"

The patch not only implements the current PBMT extension but also
considers future scalability. It uses 3 words of image header to
store 8 memory types' values plus a mask value. That means there
are still 5 memory types reserved for future scalability.

This patch does not introduce any manufacturer-defined attribute
codes, because RISC-V requires manufacturers to follow the PBMT
extension specification. However, if the manufacturer implements
a custom PBMT code, it can be compatible by modifying
image_hdr.pbmt[3] during the startup phase.

The patch is trying to keep both below works together:
 - "Linux Keep real hardware work" (Allwinner D1 needs custom mt)
 - "riscv spec acceptance policy" (Svpbmt extension)

Link: https://lists.riscv.org/g/tech-virt-mem/topic/simplified_latest_pbmt/83389883?p=,,,20,0,0,0::recentpostdate%2Fsticky,,,20,2,0,83389883
Signed-off-by: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
Signed-off-by: Liu Shaohua <liush@xxxxxxxxxxxxxxxxx>
Cc: Palmer Dabbelt <palmerdabbelt@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Anup Patel <anup.patel@xxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
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>
---
 arch/riscv/include/asm/image.h        |  6 ++--
 arch/riscv/include/asm/pgtable-64.h   |  8 +++--
 arch/riscv/include/asm/pgtable-bits.h | 55 +++++++++++++++++++++++++++++++++--
 arch/riscv/include/asm/pgtable.h      | 17 +++++------
 arch/riscv/kernel/head.S              |  6 ++++
 arch/riscv/mm/init.c                  | 46 +++++++++++++++++++++++++++++
 6 files changed, 119 insertions(+), 19 deletions(-)

diff --git a/arch/riscv/include/asm/image.h b/arch/riscv/include/asm/image.h
index e0b319a..15e13de 100644
--- a/arch/riscv/include/asm/image.h
+++ b/arch/riscv/include/asm/image.h
@@ -38,8 +38,7 @@
  * @image_size:		Effective Image size (little endian)
  * @flags:		kernel flags (little endian)
  * @version:		version
- * @res1:		reserved
- * @res2:		reserved
+ * @pbmt[3]:		Page-Based Memory Types (Encode within 3 words)
  * @magic:		Magic number (RISC-V specific; deprecated)
  * @magic2:		Magic number 2 (to match the ARM64 'magic' field pos)
  * @res3:		reserved (will be used for PE COFF offset)
@@ -55,8 +54,7 @@ struct riscv_image_header {
 	u64 image_size;
 	u64 flags;
 	u32 version;
-	u32 res1;
-	u64 res2;
+	u32 pbmt[3];
 	u64 magic;
 	u32 magic2;
 	u32 res3;
diff --git a/arch/riscv/include/asm/pgtable-64.h b/arch/riscv/include/asm/pgtable-64.h
index e3b7c5d..ecf10bc 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 unsigned long pud_page_vaddr(pud_t pud)
 {
-	return (unsigned long)pfn_to_virt(pud_val(pud) >> _PAGE_PFN_SHIFT);
+	return (unsigned long)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 pmd_ERROR(e) \
diff --git a/arch/riscv/include/asm/pgtable-bits.h b/arch/riscv/include/asm/pgtable-bits.h
index 2ee4139..1aadd00 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 +24,49 @@
 #define _PAGE_DIRTY     (1 << 7)    /* Set by hardware on any write */
 #define _PAGE_SOFT      (1 << 8)    /* Reserved for software */
 
+#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:
+ *  - WB: 00
+ *  - NC: 01
+ *  - IO: 11
+ */
+#define _PAGE_MT_MASK		(0x3 << 61)
+#define _PAGE_MT_WB		(0x0 << 61)
+#define _PAGE_MT_NC		(0x1 << 61)
+#define _PAGE_MT_IO		(0x2 << 61)
+
+/*
+ * Using 96 bits of image header to encode memory types. Every types occupy 10
+ * bits and every word contains 3 elements.
+ *  - word0: dma   + mt[0] + mt[1]
+ *  - word1: mt[2] + mt[3] + mt[4]
+ *  - word2: mt[5] + mt[6] + mt[7]
+ */
+#define _IMG_HDR_MT_WORD0	(_PAGE_MT_MASK	>> 54) | \
+				(_PAGE_MT_WB	>> 44) | \
+				(_PAGE_MT_NC	>> 34)
+#define _IMG_HDR_MT_WORD1	(_PAGE_MT_IO	>> 54) | \
+				(0		>> 44) | \
+				(0		>> 34)
+#define _IMG_HDR_MT_WORD2	(0		>> 54) | \
+				(0		>> 44) | \
+				(0		>> 34)
+
+#define _PAGE_DMA_MASK		__riscv_pbmt.mask
+#define _PAGE_DMA_WB		__riscv_pbmt.mt[0]
+#define _PAGE_DMA_NC		__riscv_pbmt.mt[1]
+#define _PAGE_DMA_IO		__riscv_pbmt.mt[2]
+#else
+#define _PAGE_DMA_MASK		0
+#define _PAGE_DMA_WB		0
+#define _PAGE_DMA_NC		0
+#define _PAGE_DMA_IO		0
+#endif
+
 #define _PAGE_SPECIAL   _PAGE_SOFT
 #define _PAGE_TABLE     _PAGE_PRESENT
 
@@ -35,10 +78,18 @@
 
 #define _PAGE_PFN_SHIFT 10
 
+#ifndef __ASSEMBLY__
+extern struct __riscv_pbmt_struct {
+	unsigned long mask;
+	unsigned long mt[8];
+} __riscv_pbmt;
+#endif
+
 /* 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 46a8aa6..d59c1d3 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -116,7 +116,7 @@
 #define USER_PTRS_PER_PGD   (TASK_SIZE / PGDIR_SIZE)
 
 /* Page protection bits */
-#define _PAGE_BASE	(_PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_USER)
+#define _PAGE_BASE	(_PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_USER | _PAGE_DMA_WB)
 
 #define PAGE_NONE		__pgprot(_PAGE_PROT_NONE)
 #define PAGE_READ		__pgprot(_PAGE_BASE | _PAGE_READ)
@@ -137,7 +137,8 @@
 				| _PAGE_PRESENT \
 				| _PAGE_ACCESSED \
 				| _PAGE_DIRTY \
-				| _PAGE_GLOBAL)
+				| _PAGE_GLOBAL \
+				| _PAGE_DMA_WB)
 
 #define PAGE_KERNEL		__pgprot(_PAGE_KERNEL)
 #define PAGE_KERNEL_READ	__pgprot(_PAGE_KERNEL & ~_PAGE_WRITE)
@@ -147,11 +148,7 @@
 
 #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)
 
 extern pgd_t swapper_pg_dir[];
 
@@ -231,12 +228,12 @@ 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)
@@ -252,7 +249,7 @@ 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))
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index 89cc58a..6037df9 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -63,8 +63,14 @@ ENTRY(_start)
 	.dword _end - _start
 	.dword __HEAD_FLAGS
 	.word RISCV_HEADER_VERSION
+#ifdef CONFIG_64BIT
+	.word _IMG_HDR_MT_WORD0
+	.word _IMG_HDR_MT_WORD1
+	.word _IMG_HDR_MT_WORD2
+#else
 	.word 0
 	.dword 0
+#endif
 	.ascii RISCV_IMAGE_MAGIC
 	.balign 4
 	.ascii RISCV_IMAGE_MAGIC2
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 4b55046..8c1978a 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -21,6 +21,7 @@
 #include <linux/crash_dump.h>
 
 #include <asm/fixmap.h>
+#include <asm/image.h>
 #include <asm/tlbflush.h>
 #include <asm/sections.h>
 #include <asm/soc.h>
@@ -554,6 +555,27 @@ static void __init create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size, bo
 }
 #endif
 
+#ifdef CONFIG_64BIT
+#define PBMT_HDR_TO_MT(val, off)	((unsigned long)((val >> off) & 0x3ff) << 54)
+
+static void __init setup_pbmt(void)
+{
+	unsigned int *pbmt = ((struct riscv_image_header *)(&_start))->pbmt;
+
+	__riscv_pbmt.mask  = PBMT_HDR_TO_MT(pbmt[0], 0);
+	__riscv_pbmt.mt[0] = PBMT_HDR_TO_MT(pbmt[0], 10);
+	__riscv_pbmt.mt[1] = PBMT_HDR_TO_MT(pbmt[0], 20);
+
+	__riscv_pbmt.mt[2] = PBMT_HDR_TO_MT(pbmt[1], 0);
+	__riscv_pbmt.mt[3] = PBMT_HDR_TO_MT(pbmt[1], 10);
+	__riscv_pbmt.mt[4] = PBMT_HDR_TO_MT(pbmt[1], 20);
+
+	__riscv_pbmt.mt[5] = PBMT_HDR_TO_MT(pbmt[2], 0);
+	__riscv_pbmt.mt[6] = PBMT_HDR_TO_MT(pbmt[2], 10);
+	__riscv_pbmt.mt[7] = PBMT_HDR_TO_MT(pbmt[2], 20);
+}
+#endif
+
 static void __init setup_protection_map(void)
 {
 	protection_map[0]  = __P000;
@@ -582,6 +604,9 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 	pmd_t fix_bmap_spmd, fix_bmap_epmd;
 #endif
 
+#ifdef CONFIG_64BIT
+	setup_pbmt();
+#endif
 	setup_protection_map();
 
 #ifdef CONFIG_XIP_KERNEL
@@ -915,6 +940,19 @@ void __init paging_init(void)
 	setup_vm_final();
 }
 
+#ifdef CONFIG_64BIT
+void __init pbmt_init(void)
+{
+	struct device_node *cpu;
+
+	cpu = of_find_node_by_path("/cpus");
+	if (!cpu || of_property_read_bool(cpu, "pbmt-extension"))
+		return;
+
+	memset(&__riscv_pbmt, 0, sizeof(__riscv_pbmt));
+}
+#endif
+
 void __init misc_mem_init(void)
 {
 	early_memtest(min_low_pfn << PAGE_SHIFT, max_low_pfn << PAGE_SHIFT);
@@ -925,6 +963,9 @@ void __init misc_mem_init(void)
 	reserve_crashkernel();
 #endif
 	memblock_dump_all();
+#ifdef CONFIG_64BIT
+	pbmt_init();
+#endif
 }
 
 #ifdef CONFIG_SPARSEMEM_VMEMMAP
@@ -934,3 +975,8 @@ 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_pbmt_struct __riscv_pbmt __ro_after_init;
+EXPORT_SYMBOL(__riscv_pbmt);
+#endif
-- 
2.7.4




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