| Message ID | 20221213060204.27286-1-alexghiti@rivosinc.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Palmer Dabbelt |
| Headers | show |
| Series | [v3] riscv: Use PUD/P4D/PGD pages for the linear mapping | expand |
| Context | Check | Description |
|---|---|---|
| conchuod/tree_selection | fail | Guessing tree name failed |
On Tue, Dec 13, 2022 at 07:02:04AM +0100, Alexandre Ghiti wrote: > During the early page table creation, we used to set the mapping for > PAGE_OFFSET to the kernel load address: but the kernel load address is > always offseted by PMD_SIZE which makes it impossible to use PUD/P4D/PGD > pages as this physical address is not aligned on PUD/P4D/PGD size (whereas > PAGE_OFFSET is). > > But actually we don't have to establish this mapping (ie set va_pa_offset) > that early in the boot process because: > > - first, setup_vm installs a temporary kernel mapping and among other > things, discovers the system memory, > - then, setup_vm_final creates the final kernel mapping and takes > advantage of the discovered system memory to create the linear > mapping. > > During the first phase, we don't know the start of the system memory and > then until the second phase is finished, we can't use the linear mapping at > all and phys_to_virt/virt_to_phys translations must not be used because it > would result in a different translation from the 'real' one once the final > mapping is installed. > > So here we simply delay the initialization of va_pa_offset to after the > system memory discovery. But to make sure noone uses the linear mapping > before, we add some guard in the DEBUG_VIRTUAL config. > > Finally we can use PUD/P4D/PGD hugepages when possible, which will result > in a better TLB utilization. > > Note that we rely on the firmware to protect itself using PMP. > > Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com> > --- > > v3: > - Change the comment about initrd_start VA conversion so that it fits > ARM64 and RISCV64 (and others in the future if needed), as suggested > by Rob > > v2: > - Add a comment on why RISCV64 does not need to set initrd_start/end that > early in the boot process, as asked by Rob > > Note that this patch is rebased on top of: > [PATCH v1 1/1] riscv: mm: call best_map_size many times during linear-mapping > > arch/riscv/include/asm/page.h | 16 ++++++++++++++++ > arch/riscv/mm/init.c | 25 +++++++++++++++++++------ > arch/riscv/mm/physaddr.c | 16 ++++++++++++++++ > drivers/of/fdt.c | 11 ++++++----- Acked-by: Rob Herring <robh@kernel.org> # DT bits > 4 files changed, 57 insertions(+), 11 deletions(-)
On Tue, Dec 13, 2022 at 07:02:04AM +0100, Alexandre Ghiti wrote: > During the early page table creation, we used to set the mapping for > PAGE_OFFSET to the kernel load address: but the kernel load address is > always offseted by PMD_SIZE which makes it impossible to use PUD/P4D/PGD > pages as this physical address is not aligned on PUD/P4D/PGD size (whereas > PAGE_OFFSET is). > > But actually we don't have to establish this mapping (ie set va_pa_offset) > that early in the boot process because: > > - first, setup_vm installs a temporary kernel mapping and among other > things, discovers the system memory, > - then, setup_vm_final creates the final kernel mapping and takes > advantage of the discovered system memory to create the linear > mapping. > > During the first phase, we don't know the start of the system memory and > then until the second phase is finished, we can't use the linear mapping at > all and phys_to_virt/virt_to_phys translations must not be used because it > would result in a different translation from the 'real' one once the final > mapping is installed. > > So here we simply delay the initialization of va_pa_offset to after the > system memory discovery. But to make sure noone uses the linear mapping > before, we add some guard in the DEBUG_VIRTUAL config. > > Finally we can use PUD/P4D/PGD hugepages when possible, which will result > in a better TLB utilization. > > Note that we rely on the firmware to protect itself using PMP. > > Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com> > --- > > v3: > - Change the comment about initrd_start VA conversion so that it fits > ARM64 and RISCV64 (and others in the future if needed), as suggested > by Rob > > v2: > - Add a comment on why RISCV64 does not need to set initrd_start/end that > early in the boot process, as asked by Rob > > Note that this patch is rebased on top of: > [PATCH v1 1/1] riscv: mm: call best_map_size many times during linear-mapping Hey Alex, unfortunately I could not get this to apply either (I tried a riscv/for-next & Linus' tree). The above patch should be in both, so idk: git am -3 v3_20221213_alexghiti_riscv_use_pud_p4d_pgd_pages_for_the_linear_mapping.mbx Applying: riscv: Use PUD/P4D/PGD pages for the linear mapping error: sha1 information is lacking or useless (arch/riscv/mm/init.c). error: could not build fake ancestor Patch failed at 0001 riscv: Use PUD/P4D/PGD pages for the linear mapping I assume it'll need a rebase after -rc1? It's really nice to see someone looking at this early code, from the bit of digging around that I've done chasing bugs it feels like it needs it- so thanks!
On 12/22/22 17:21, Conor Dooley wrote: > On Tue, Dec 13, 2022 at 07:02:04AM +0100, Alexandre Ghiti wrote: >> During the early page table creation, we used to set the mapping for >> PAGE_OFFSET to the kernel load address: but the kernel load address is >> always offseted by PMD_SIZE which makes it impossible to use PUD/P4D/PGD >> pages as this physical address is not aligned on PUD/P4D/PGD size (whereas >> PAGE_OFFSET is). >> >> But actually we don't have to establish this mapping (ie set va_pa_offset) >> that early in the boot process because: >> >> - first, setup_vm installs a temporary kernel mapping and among other >> things, discovers the system memory, >> - then, setup_vm_final creates the final kernel mapping and takes >> advantage of the discovered system memory to create the linear >> mapping. >> >> During the first phase, we don't know the start of the system memory and >> then until the second phase is finished, we can't use the linear mapping at >> all and phys_to_virt/virt_to_phys translations must not be used because it >> would result in a different translation from the 'real' one once the final >> mapping is installed. >> >> So here we simply delay the initialization of va_pa_offset to after the >> system memory discovery. But to make sure noone uses the linear mapping >> before, we add some guard in the DEBUG_VIRTUAL config. >> >> Finally we can use PUD/P4D/PGD hugepages when possible, which will result >> in a better TLB utilization. >> >> Note that we rely on the firmware to protect itself using PMP. >> >> Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com> >> --- >> >> v3: >> - Change the comment about initrd_start VA conversion so that it fits >> ARM64 and RISCV64 (and others in the future if needed), as suggested >> by Rob >> >> v2: >> - Add a comment on why RISCV64 does not need to set initrd_start/end that >> early in the boot process, as asked by Rob >> >> Note that this patch is rebased on top of: >> [PATCH v1 1/1] riscv: mm: call best_map_size many times during linear-mapping > > Hey Alex, unfortunately I could not get this to apply either (I tried a > riscv/for-next & Linus' tree). > The above patch should be in both, so idk: > git am -3 v3_20221213_alexghiti_riscv_use_pud_p4d_pgd_pages_for_the_linear_mapping.mbx > Applying: riscv: Use PUD/P4D/PGD pages for the linear mapping > error: sha1 information is lacking or useless (arch/riscv/mm/init.c). > error: could not build fake ancestor > Patch failed at 0001 riscv: Use PUD/P4D/PGD pages for the linear mapping That's because my CONFIG_DEBUG_VIRTUAL fix got applied first. This patch applies cleanly after: git revert -m1 61b2f0bdaa3c7e6956fdac0a7c1e8284b9b81d1d though you'll get one trivial conflict if you try to undo the revert. Regards, Samuel
On 12/13/22 00:02, Alexandre Ghiti wrote: > During the early page table creation, we used to set the mapping for > PAGE_OFFSET to the kernel load address: but the kernel load address is > always offseted by PMD_SIZE which makes it impossible to use PUD/P4D/PGD > pages as this physical address is not aligned on PUD/P4D/PGD size (whereas > PAGE_OFFSET is). > > But actually we don't have to establish this mapping (ie set va_pa_offset) > that early in the boot process because: > > - first, setup_vm installs a temporary kernel mapping and among other > things, discovers the system memory, > - then, setup_vm_final creates the final kernel mapping and takes > advantage of the discovered system memory to create the linear > mapping. > > During the first phase, we don't know the start of the system memory and > then until the second phase is finished, we can't use the linear mapping at > all and phys_to_virt/virt_to_phys translations must not be used because it > would result in a different translation from the 'real' one once the final > mapping is installed. > > So here we simply delay the initialization of va_pa_offset to after the > system memory discovery. But to make sure noone uses the linear mapping > before, we add some guard in the DEBUG_VIRTUAL config. > > Finally we can use PUD/P4D/PGD hugepages when possible, which will result > in a better TLB utilization. > > Note that we rely on the firmware to protect itself using PMP. > > Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com> > --- > > v3: > - Change the comment about initrd_start VA conversion so that it fits > ARM64 and RISCV64 (and others in the future if needed), as suggested > by Rob > > v2: > - Add a comment on why RISCV64 does not need to set initrd_start/end that > early in the boot process, as asked by Rob > > Note that this patch is rebased on top of: > [PATCH v1 1/1] riscv: mm: call best_map_size many times during linear-mapping > > arch/riscv/include/asm/page.h | 16 ++++++++++++++++ > arch/riscv/mm/init.c | 25 +++++++++++++++++++------ > arch/riscv/mm/physaddr.c | 16 ++++++++++++++++ > drivers/of/fdt.c | 11 ++++++----- > 4 files changed, 57 insertions(+), 11 deletions(-) This works nicely on D1! Before: MemTotal: 490680 kB after: MemTotal: 492472 kB and I tested booting with CONFIG_DEBUG_VIRTUAL without issue as well. Reviewed-by: Samuel Holland <samuel@sholland.org> Tested-by: Samuel Holland <samuel@sholland.org>
diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h index ac70b0fd9a9a..f3af526a149f 100644 --- a/arch/riscv/include/asm/page.h +++ b/arch/riscv/include/asm/page.h @@ -90,6 +90,14 @@ typedef struct page *pgtable_t; #define PTE_FMT "%08lx" #endif +#ifdef CONFIG_64BIT +/* + * We override this value as its generic definition uses __pa too early in + * the boot process (before kernel_map.va_pa_offset is set). + */ +#define MIN_MEMBLOCK_ADDR 0 +#endif + #ifdef CONFIG_MMU extern unsigned long riscv_pfn_base; #define ARCH_PFN_OFFSET (riscv_pfn_base) @@ -122,7 +130,11 @@ extern phys_addr_t phys_ram_base; #define is_linear_mapping(x) \ ((x) >= PAGE_OFFSET && (!IS_ENABLED(CONFIG_64BIT) || (x) < PAGE_OFFSET + KERN_VIRT_SIZE)) +#ifndef CONFIG_DEBUG_VIRTUAL #define linear_mapping_pa_to_va(x) ((void *)((unsigned long)(x) + kernel_map.va_pa_offset)) +#else +void *linear_mapping_pa_to_va(unsigned long x); +#endif #define kernel_mapping_pa_to_va(y) ({ \ unsigned long _y = y; \ (IS_ENABLED(CONFIG_XIP_KERNEL) && _y < phys_ram_base) ? \ @@ -131,7 +143,11 @@ extern phys_addr_t phys_ram_base; }) #define __pa_to_va_nodebug(x) linear_mapping_pa_to_va(x) +#ifndef CONFIG_DEBUG_VIRTUAL #define linear_mapping_va_to_pa(x) ((unsigned long)(x) - kernel_map.va_pa_offset) +#else +phys_addr_t linear_mapping_va_to_pa(unsigned long x); +#endif #define kernel_mapping_va_to_pa(y) ({ \ unsigned long _y = y; \ (IS_ENABLED(CONFIG_XIP_KERNEL) && _y < kernel_map.virt_addr + XIP_OFFSET) ? \ diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c index 1b76d3fe4e26..58bcf395efdc 100644 --- a/arch/riscv/mm/init.c +++ b/arch/riscv/mm/init.c @@ -213,6 +213,14 @@ static void __init setup_bootmem(void) phys_ram_end = memblock_end_of_DRAM(); if (!IS_ENABLED(CONFIG_XIP_KERNEL)) phys_ram_base = memblock_start_of_DRAM(); + + /* + * Any use of __va/__pa before this point is wrong as we did not know the + * start of DRAM before. + */ + kernel_map.va_pa_offset = PAGE_OFFSET - phys_ram_base; + riscv_pfn_base = PFN_DOWN(phys_ram_base); + /* * memblock allocator is not aware of the fact that last 4K bytes of * the addressable memory can not be mapped because of IS_ERR_VALUE @@ -672,9 +680,16 @@ void __init create_pgd_mapping(pgd_t *pgdp, static uintptr_t __init best_map_size(phys_addr_t base, phys_addr_t size) { - /* Upgrade to PMD_SIZE mappings whenever possible */ - base &= PMD_SIZE - 1; - if (!base && size >= PMD_SIZE) + if (!(base & (PGDIR_SIZE - 1)) && size >= PGDIR_SIZE) + return PGDIR_SIZE; + + if (!(base & (P4D_SIZE - 1)) && size >= P4D_SIZE) + return P4D_SIZE; + + if (!(base & (PUD_SIZE - 1)) && size >= PUD_SIZE) + return PUD_SIZE; + + if (!(base & (PMD_SIZE - 1)) && size >= PMD_SIZE) return PMD_SIZE; return PAGE_SIZE; @@ -983,11 +998,9 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa) set_satp_mode(); #endif - kernel_map.va_pa_offset = PAGE_OFFSET - kernel_map.phys_addr; + kernel_map.va_pa_offset = 0UL; kernel_map.va_kernel_pa_offset = kernel_map.virt_addr - kernel_map.phys_addr; - riscv_pfn_base = PFN_DOWN(kernel_map.phys_addr); - /* * The default maximal physical memory size is KERN_VIRT_SIZE for 32-bit * kernel, whereas for 64-bit kernel, the end of the virtual address diff --git a/arch/riscv/mm/physaddr.c b/arch/riscv/mm/physaddr.c index 19cf25a74ee2..5ae4bd166e25 100644 --- a/arch/riscv/mm/physaddr.c +++ b/arch/riscv/mm/physaddr.c @@ -33,3 +33,19 @@ phys_addr_t __phys_addr_symbol(unsigned long x) return __va_to_pa_nodebug(x); } EXPORT_SYMBOL(__phys_addr_symbol); + +phys_addr_t linear_mapping_va_to_pa(unsigned long x) +{ + BUG_ON(!kernel_map.va_pa_offset); + + return ((unsigned long)(x) - kernel_map.va_pa_offset); +} +EXPORT_SYMBOL(linear_mapping_va_to_pa); + +void *linear_mapping_pa_to_va(unsigned long x) +{ + BUG_ON(!kernel_map.va_pa_offset); + + return ((void *)((unsigned long)(x) + kernel_map.va_pa_offset)); +} +EXPORT_SYMBOL(linear_mapping_pa_to_va); diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c index 7b571a631639..c45aaa3458a7 100644 --- a/drivers/of/fdt.c +++ b/drivers/of/fdt.c @@ -891,12 +891,13 @@ const void * __init of_flat_dt_match_machine(const void *default_match, static void __early_init_dt_declare_initrd(unsigned long start, unsigned long end) { - /* ARM64 would cause a BUG to occur here when CONFIG_DEBUG_VM is - * enabled since __va() is called too early. ARM64 does make use - * of phys_initrd_start/phys_initrd_size so we can skip this - * conversion. + /* + * __va() is not yet available this early on some platforms. In that + * case, the platform uses phys_initrd_start/phys_initrd_size instead + * and does the VA conversion itself. */ - if (!IS_ENABLED(CONFIG_ARM64)) { + if (!IS_ENABLED(CONFIG_ARM64) && + !(IS_ENABLED(CONFIG_RISCV) && IS_ENABLED(CONFIG_64BIT))) { initrd_start = (unsigned long)__va(start); initrd_end = (unsigned long)__va(end); initrd_below_start_ok = 1;
During the early page table creation, we used to set the mapping for PAGE_OFFSET to the kernel load address: but the kernel load address is always offseted by PMD_SIZE which makes it impossible to use PUD/P4D/PGD pages as this physical address is not aligned on PUD/P4D/PGD size (whereas PAGE_OFFSET is). But actually we don't have to establish this mapping (ie set va_pa_offset) that early in the boot process because: - first, setup_vm installs a temporary kernel mapping and among other things, discovers the system memory, - then, setup_vm_final creates the final kernel mapping and takes advantage of the discovered system memory to create the linear mapping. During the first phase, we don't know the start of the system memory and then until the second phase is finished, we can't use the linear mapping at all and phys_to_virt/virt_to_phys translations must not be used because it would result in a different translation from the 'real' one once the final mapping is installed. So here we simply delay the initialization of va_pa_offset to after the system memory discovery. But to make sure noone uses the linear mapping before, we add some guard in the DEBUG_VIRTUAL config. Finally we can use PUD/P4D/PGD hugepages when possible, which will result in a better TLB utilization. Note that we rely on the firmware to protect itself using PMP. Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com> --- v3: - Change the comment about initrd_start VA conversion so that it fits ARM64 and RISCV64 (and others in the future if needed), as suggested by Rob v2: - Add a comment on why RISCV64 does not need to set initrd_start/end that early in the boot process, as asked by Rob Note that this patch is rebased on top of: [PATCH v1 1/1] riscv: mm: call best_map_size many times during linear-mapping arch/riscv/include/asm/page.h | 16 ++++++++++++++++ arch/riscv/mm/init.c | 25 +++++++++++++++++++------ arch/riscv/mm/physaddr.c | 16 ++++++++++++++++ drivers/of/fdt.c | 11 ++++++----- 4 files changed, 57 insertions(+), 11 deletions(-)