Linux-RISC-V Archive on lore.kernel.org
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From: Atish Patra <atish.patra@wdc.com>
To: linux-kernel@vger.kernel.org
Cc: Mark Rutland <mark.rutland@arm.com>,
	linux-efi@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
	Kees Cook <keescook@chromium.org>, Nick Hu <nickhu@andestech.com>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Anup Patel <anup.patel@wdc.com>, Yash Shah <yash.shah@sifive.com>,
	Ard Biesheuvel <ardb@kernel.org>,
	Atish Patra <atish.patra@wdc.com>,
	Arvind Sankar <nivedita@alum.mit.edu>,
	Palmer Dabbelt <palmer@dabbelt.com>, Zong Li <zong.li@sifive.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Greentime Hu <greentime.hu@sifive.com>,
	linux-riscv@lists.infradead.org, Will Deacon <will@kernel.org>,
	Ingo Molnar <mingo@kernel.org>, Mike Rapoport <rppt@kernel.org>
Subject: [RFT PATCH v4 1/9] RISC-V: Move DT mapping outof fixmap
Date: Wed, 29 Jul 2020 16:36:27 -0700
Message-ID: <20200729233635.14406-2-atish.patra@wdc.com> (raw)
In-Reply-To: <20200729233635.14406-1-atish.patra@wdc.com>

From: Anup Patel <anup.patel@wdc.com>

Currently, RISC-V reserves 1MB of fixmap memory for device tree. However,
it maps only single PMD (2MB) space for fixmap which leaves only < 1MB space
left for other kernel features such as early ioremap which requires fixmap
as well. The fixmap size can be increased by another 2MB but it brings
additional complexity and changes the virtual memory layout as well.
If we require some additional feature requiring fixmap again, it has to be
moved again.

Technically, DT doesn't need a fixmap as the memory occupied by the DT is
only used during boot. That's why, We map device tree in early page table
using two consecutive PGD mappings at lower addresses (< PAGE_OFFSET).
This frees lot of space in fixmap and also makes maximum supported
device tree size supported as PGDIR_SIZE. Thus, init memory section can be used
for the same purpose as well. This simplifies fixmap implementation.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Signed-off-by: Atish Patra <atish.patra@wdc.com>
---
 arch/riscv/include/asm/fixmap.h  |  3 ---
 arch/riscv/include/asm/pgtable.h |  1 +
 arch/riscv/kernel/head.S         |  1 -
 arch/riscv/kernel/head.h         |  2 --
 arch/riscv/kernel/setup.c        |  9 +++++++--
 arch/riscv/mm/init.c             | 26 ++++++++++++--------------
 6 files changed, 20 insertions(+), 22 deletions(-)

diff --git a/arch/riscv/include/asm/fixmap.h b/arch/riscv/include/asm/fixmap.h
index 1ff075a8dfc7..11613f38228a 100644
--- a/arch/riscv/include/asm/fixmap.h
+++ b/arch/riscv/include/asm/fixmap.h
@@ -22,9 +22,6 @@
  */
 enum fixed_addresses {
 	FIX_HOLE,
-#define FIX_FDT_SIZE	SZ_1M
-	FIX_FDT_END,
-	FIX_FDT = FIX_FDT_END + FIX_FDT_SIZE / PAGE_SIZE - 1,
 	FIX_PTE,
 	FIX_PMD,
 	FIX_TEXT_POKE1,
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index eaea1f717010..815f8c959dd4 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -464,6 +464,7 @@ static inline void __kernel_map_pages(struct page *page, int numpages, int enabl
 #define kern_addr_valid(addr)   (1) /* FIXME */
 
 extern void *dtb_early_va;
+extern uintptr_t dtb_early_pa;
 void setup_bootmem(void);
 void paging_init(void);
 
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index d0c5c316e9bb..eb123eda3663 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -250,7 +250,6 @@ clear_bss_done:
 #endif
 	/* Start the kernel */
 	call soc_early_init
-	call parse_dtb
 	tail start_kernel
 
 .Lsecondary_start:
diff --git a/arch/riscv/kernel/head.h b/arch/riscv/kernel/head.h
index 105fb0496b24..b48dda3d04f6 100644
--- a/arch/riscv/kernel/head.h
+++ b/arch/riscv/kernel/head.h
@@ -16,6 +16,4 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa);
 extern void *__cpu_up_stack_pointer[];
 extern void *__cpu_up_task_pointer[];
 
-void __init parse_dtb(void);
-
 #endif /* __ASM_HEAD_H */
diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index f04373be54a6..6a0ee2405813 100644
--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -49,8 +49,9 @@ atomic_t hart_lottery __section(.sdata);
 unsigned long boot_cpu_hartid;
 static DEFINE_PER_CPU(struct cpu, cpu_devices);
 
-void __init parse_dtb(void)
+static void __init parse_dtb(void)
 {
+	/* Early scan of device tree from init memory */
 	if (early_init_dt_scan(dtb_early_va))
 		return;
 
@@ -63,6 +64,7 @@ void __init parse_dtb(void)
 
 void __init setup_arch(char **cmdline_p)
 {
+	parse_dtb();
 	init_mm.start_code = (unsigned long) _stext;
 	init_mm.end_code   = (unsigned long) _etext;
 	init_mm.end_data   = (unsigned long) _edata;
@@ -77,7 +79,10 @@ void __init setup_arch(char **cmdline_p)
 #if IS_ENABLED(CONFIG_BUILTIN_DTB)
 	unflatten_and_copy_device_tree();
 #else
-	unflatten_device_tree();
+	if (early_init_dt_verify(__va(dtb_early_pa)))
+		unflatten_device_tree();
+	else
+		pr_err("No DTB found in kernel mappings\n");
 #endif
 	clint_init_boot_cpu();
 
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 79e9d55bdf1a..9c5f3e35adc2 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -28,7 +28,9 @@ unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
 EXPORT_SYMBOL(empty_zero_page);
 
 extern char _start[];
-void *dtb_early_va;
+#define DTB_EARLY_BASE_VA      PGDIR_SIZE
+void *dtb_early_va __initdata;
+uintptr_t dtb_early_pa __initdata;
 
 static void __init zone_sizes_init(void)
 {
@@ -141,8 +143,6 @@ static void __init setup_initrd(void)
 }
 #endif /* CONFIG_BLK_DEV_INITRD */
 
-static phys_addr_t dtb_early_pa __initdata;
-
 void __init setup_bootmem(void)
 {
 	struct memblock_region *reg;
@@ -399,7 +399,7 @@ static uintptr_t __init best_map_size(phys_addr_t base, phys_addr_t size)
 
 asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 {
-	uintptr_t va, end_va;
+	uintptr_t va, pa, end_va;
 	uintptr_t load_pa = (uintptr_t)(&_start);
 	uintptr_t load_sz = (uintptr_t)(&_end) - load_pa;
 	uintptr_t map_size = best_map_size(load_pa, MAX_EARLY_MAPPING_SIZE);
@@ -448,16 +448,13 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 				   load_pa + (va - PAGE_OFFSET),
 				   map_size, PAGE_KERNEL_EXEC);
 
-	/* Create fixed mapping for early FDT parsing */
-	end_va = __fix_to_virt(FIX_FDT) + FIX_FDT_SIZE;
-	for (va = __fix_to_virt(FIX_FDT); va < end_va; va += PAGE_SIZE)
-		create_pte_mapping(fixmap_pte, va,
-				   dtb_pa + (va - __fix_to_virt(FIX_FDT)),
-				   PAGE_SIZE, PAGE_KERNEL);
-
-	/* Save pointer to DTB for early FDT parsing */
-	dtb_early_va = (void *)fix_to_virt(FIX_FDT) + (dtb_pa & ~PAGE_MASK);
-	/* Save physical address for memblock reservation */
+	/* Create two consecutive PGD mappings for FDT early scan */
+	pa = dtb_pa & ~(PGDIR_SIZE - 1);
+	create_pgd_mapping(early_pg_dir, DTB_EARLY_BASE_VA,
+			   pa, PGDIR_SIZE, PAGE_KERNEL);
+	create_pgd_mapping(early_pg_dir, DTB_EARLY_BASE_VA + PGDIR_SIZE,
+			   pa + PGDIR_SIZE, PGDIR_SIZE, PAGE_KERNEL);
+	dtb_early_va = (void *)DTB_EARLY_BASE_VA + (dtb_pa & (PGDIR_SIZE - 1));
 	dtb_early_pa = dtb_pa;
 }
 
@@ -516,6 +513,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 #else
 	dtb_early_va = (void *)dtb_pa;
 #endif
+	dtb_early_pa = dtb_pa;
 }
 
 static inline void setup_vm_final(void)
-- 
2.24.0


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Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-29 23:36 [RFT PATCH v4 0/9] Add UEFI support for RISC-V Atish Patra
2020-07-29 23:36 ` Atish Patra [this message]
2020-07-29 23:36 ` [RFT PATCH v4 2/9] RISC-V: Add early ioremap support Atish Patra
2020-07-29 23:36 ` [RFT PATCH v4 3/9] RISC-V: Implement late mapping page table allocation functions Atish Patra
2020-07-30  9:14   ` Mike Rapoport
2020-08-03  0:55     ` Atish Patra
2020-07-29 23:36 ` [RFT PATCH v4 4/9] include: pe.h: Add RISC-V related PE definition Atish Patra
2020-07-29 23:36 ` [RFT PATCH v4 5/9] RISC-V: Add PE/COFF header for EFI stub Atish Patra
2020-07-29 23:36 ` [RFT PATCH v4 6/9] RISC-V: Add EFI stub support Atish Patra
2020-07-29 23:36 ` [RFT PATCH v4 7/9] efi: Rename arm-init to efi-init common for all arch Atish Patra
2020-07-29 23:36 ` [RFT PATCH v4 8/9] RISC-V: Add EFI runtime services Atish Patra
2020-07-29 23:36 ` [RFT PATCH v4 9/9] RISC-V: Add page table dump support for uefi Atish Patra
2020-07-31 13:25 ` [RFT PATCH v4 0/9] Add UEFI support for RISC-V Ard Biesheuvel

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