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SubjectRe: [PATCH v8 06/11] RISC-V: Move relocate and few other functions out of __init
On Tue, Feb 11, 2020 at 8:18 PM Anup Patel <anup@brainfault.org> wrote:
>
> On Wed, Feb 12, 2020 at 7:21 AM Atish Patra <atish.patra@wdc.com> wrote:
> >
> > The secondary hart booting and relocation code are under .init section.
> > As a result, it will be freed once kernel booting is done. However,
> > ordered booting protocol and CPU hotplug always requires these sections
>
> I think you meant "... require these functions" here.
>
> > to be present to bringup harts after initial kernel boot.
> >
> > Move the required sections to a different section and make sure that
>
> Same here, I think you meant "... the required functions to a
> different section ..."
>

My bad. Thanks for pointing out. Fixed.

> > they are in memory within first 2MB offset as trampoline page directory
> > only maps first 2MB.
> >
> > Signed-off-by: Atish Patra <atish.patra@wdc.com>
> > ---
> > arch/riscv/kernel/head.S | 153 +++++++++++++++++---------------
> > arch/riscv/kernel/vmlinux.lds.S | 5 +-
> > 2 files changed, 86 insertions(+), 72 deletions(-)
> >
> > diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
> > index a4242be66966..c1be597d22a1 100644
> > --- a/arch/riscv/kernel/head.S
> > +++ b/arch/riscv/kernel/head.S
> > @@ -14,7 +14,7 @@
> > #include <asm/hwcap.h>
> > #include <asm/image.h>
> >
> > -__INIT
> > +__HEAD
> > ENTRY(_start)
> > /*
> > * Image header expected by Linux boot-loaders. The image header data
> > @@ -45,8 +45,85 @@ ENTRY(_start)
> > .ascii RISCV_IMAGE_MAGIC2
> > .word 0
> >
> > -.global _start_kernel
> > -_start_kernel:
> > +.align 2
> > +#ifdef CONFIG_MMU
> > +relocate:
> > + /* Relocate return address */
> > + li a1, PAGE_OFFSET
> > + la a2, _start
> > + sub a1, a1, a2
> > + add ra, ra, a1
> > +
> > + /* Point stvec to virtual address of intruction after satp write */
> > + la a2, 1f
> > + add a2, a2, a1
> > + csrw CSR_TVEC, a2
> > +
> > + /* Compute satp for kernel page tables, but don't load it yet */
> > + srl a2, a0, PAGE_SHIFT
> > + li a1, SATP_MODE
> > + or a2, a2, a1
> > +
> > + /*
> > + * Load trampoline page directory, which will cause us to trap to
> > + * stvec if VA != PA, or simply fall through if VA == PA. We need a
> > + * full fence here because setup_vm() just wrote these PTEs and we need
> > + * to ensure the new translations are in use.
> > + */
> > + la a0, trampoline_pg_dir
> > + srl a0, a0, PAGE_SHIFT
> > + or a0, a0, a1
> > + sfence.vma
> > + csrw CSR_SATP, a0
> > +.align 2
> > +1:
> > + /* Set trap vector to spin forever to help debug */
> > + la a0, .Lsecondary_park
> > + csrw CSR_TVEC, a0
> > +
> > + /* Reload the global pointer */
> > +.option push
> > +.option norelax
> > + la gp, __global_pointer$
> > +.option pop
> > +
> > + /*
> > + * Switch to kernel page tables. A full fence is necessary in order to
> > + * avoid using the trampoline translations, which are only correct for
> > + * the first superpage. Fetching the fence is guarnteed to work
> > + * because that first superpage is translated the same way.
> > + */
> > + csrw CSR_SATP, a2
> > + sfence.vma
> > +
> > + ret
> > +#endif /* CONFIG_MMU */
> > +#ifdef CONFIG_SMP
> > + /* Set trap vector to spin forever to help debug */
> > + la a3, .Lsecondary_park
> > + csrw CSR_TVEC, a3
> > +
> > + slli a3, a0, LGREG
> > + .global secondary_start_common
> > +secondary_start_common:
> > +
> > +#ifdef CONFIG_MMU
> > + /* Enable virtual memory and relocate to virtual address */
> > + la a0, swapper_pg_dir
> > + call relocate
> > +#endif
> > + tail smp_callin
> > +#endif /* CONFIG_SMP */
> > +
> > +.Lsecondary_park:
> > + /* We lack SMP support or have too many harts, so park this hart */
> > + wfi
> > + j .Lsecondary_park
> > +
> > +END(_start)
> > +
> > + __INIT
> > +ENTRY(_start_kernel)
> > /* Mask all interrupts */
> > csrw CSR_IE, zero
> > csrw CSR_IP, zero
> > @@ -125,59 +202,6 @@ clear_bss_done:
> > call parse_dtb
> > tail start_kernel
> >
> > -#ifdef CONFIG_MMU
> > -relocate:
> > - /* Relocate return address */
> > - li a1, PAGE_OFFSET
> > - la a2, _start
> > - sub a1, a1, a2
> > - add ra, ra, a1
> > -
> > - /* Point stvec to virtual address of intruction after satp write */
> > - la a2, 1f
> > - add a2, a2, a1
> > - csrw CSR_TVEC, a2
> > -
> > - /* Compute satp for kernel page tables, but don't load it yet */
> > - srl a2, a0, PAGE_SHIFT
> > - li a1, SATP_MODE
> > - or a2, a2, a1
> > -
> > - /*
> > - * Load trampoline page directory, which will cause us to trap to
> > - * stvec if VA != PA, or simply fall through if VA == PA. We need a
> > - * full fence here because setup_vm() just wrote these PTEs and we need
> > - * to ensure the new translations are in use.
> > - */
> > - la a0, trampoline_pg_dir
> > - srl a0, a0, PAGE_SHIFT
> > - or a0, a0, a1
> > - sfence.vma
> > - csrw CSR_SATP, a0
> > -.align 2
> > -1:
> > - /* Set trap vector to spin forever to help debug */
> > - la a0, .Lsecondary_park
> > - csrw CSR_TVEC, a0
> > -
> > - /* Reload the global pointer */
> > -.option push
> > -.option norelax
> > - la gp, __global_pointer$
> > -.option pop
> > -
> > - /*
> > - * Switch to kernel page tables. A full fence is necessary in order to
> > - * avoid using the trampoline translations, which are only correct for
> > - * the first superpage. Fetching the fence is guarnteed to work
> > - * because that first superpage is translated the same way.
> > - */
> > - csrw CSR_SATP, a2
> > - sfence.vma
> > -
> > - ret
> > -#endif /* CONFIG_MMU */
> > -
> > .Lsecondary_start:
> > #ifdef CONFIG_SMP
> > /* Set trap vector to spin forever to help debug */
> > @@ -202,16 +226,10 @@ relocate:
> > beqz tp, .Lwait_for_cpu_up
> > fence
> >
> > -#ifdef CONFIG_MMU
> > - /* Enable virtual memory and relocate to virtual address */
> > - la a0, swapper_pg_dir
> > - call relocate
> > + tail secondary_start_common
> > #endif
> >
> > - tail smp_callin
> > -#endif
> > -
> > -END(_start)
> > +END(_start_kernel)
> >
> > #ifdef CONFIG_RISCV_M_MODE
> > ENTRY(reset_regs)
> > @@ -292,13 +310,6 @@ ENTRY(reset_regs)
> > END(reset_regs)
> > #endif /* CONFIG_RISCV_M_MODE */
> >
> > -.section ".text", "ax",@progbits
> > -.align 2
> > -.Lsecondary_park:
> > - /* We lack SMP support or have too many harts, so park this hart */
> > - wfi
> > - j .Lsecondary_park
> > -
> > __PAGE_ALIGNED_BSS
> > /* Empty zero page */
> > .balign PAGE_SIZE
> > diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S
> > index 12f42f96d46e..18c397953bfc 100644
> > --- a/arch/riscv/kernel/vmlinux.lds.S
> > +++ b/arch/riscv/kernel/vmlinux.lds.S
> > @@ -10,6 +10,7 @@
> > #include <asm/cache.h>
> > #include <asm/thread_info.h>
> >
> > +#include <linux/sizes.h>
> > OUTPUT_ARCH(riscv)
> > ENTRY(_start)
> >
> > @@ -20,8 +21,10 @@ SECTIONS
> > /* Beginning of code and text segment */
> > . = LOAD_OFFSET;
> > _start = .;
> > - __init_begin = .;
> > HEAD_TEXT_SECTION
> > + . = ALIGN(PAGE_SIZE);
> > +
> > + __init_begin = .;
> > INIT_TEXT_SECTION(PAGE_SIZE)
> > INIT_DATA_SECTION(16)
> > /* we have to discard exit text and such at runtime, not link time */
> > --
> > 2.24.0
> >
>
> Apart from above nit in commit description, looks good to me.
>
> Reviewed-by: Anup Patel <anup@brainfault.org>
>
> Regards,
> Anup
>


--
Regards,
Atish

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