Re: [PATCH v4 02/14] arm: add support for folded p4d page tables

From: Mike Rapoport
Date: Fri May 08 2020 - 13:44:16 EST


On Fri, May 08, 2020 at 08:53:27AM +0200, Marek Szyprowski wrote:
> Hi Mike,
>
> On 07.05.2020 18:11, Mike Rapoport wrote:
> > On Thu, May 07, 2020 at 02:16:56PM +0200, Marek Szyprowski wrote:
> >> On 14.04.2020 17:34, Mike Rapoport wrote:
> >>> From: Mike Rapoport <rppt@xxxxxxxxxxxxx>
> >>>
> >>> Implement primitives necessary for the 4th level folding, add walks of p4d
> >>> level where appropriate, and remove __ARCH_USE_5LEVEL_HACK.
> >>>
> >>> Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
> >> Today I've noticed that kexec is broken on ARM 32bit. Bisecting between
> >> current linux-next and v5.7-rc1 pointed to this commit. I've tested this
> >> on Odroid XU4 and Raspberry Pi4 boards. Here is the relevant log:
> >>
> >> # kexec --kexec-syscall -l zImage --append "$(cat /proc/cmdline)"
> >> memory_range[0]:0x40000000..0xbe9fffff
> >> memory_range[0]:0x40000000..0xbe9fffff
> >> # kexec -e
> >> kexec_core: Starting new kernel
> >> 8<--- cut here ---
> >> Unable to handle kernel paging request at virtual address c010f1f4
> >> pgd = c6817793
> >> [c010f1f4] *pgd=4000041e(bad)
> >> Internal error: Oops: 80d [#1] PREEMPT ARM
> >> Modules linked in:
> >> CPU: 0 PID: 1329 Comm: kexec Tainted: G        W
> >> 5.7.0-rc3-00127-g6cba81ed0f62 #611
> >> Hardware name: Samsung Exynos (Flattened Device Tree)
> >> PC is at machine_kexec+0x40/0xfc
> > Any chance you have the debug info in this kernel?
> > scripts/faddr2line would come handy here.
>
> # ./scripts/faddr2line --list vmlinux machine_kexec+0x40
> machine_kexec+0x40/0xf8:
>
> machine_kexec at arch/arm/kernel/machine_kexec.c:182
>  177            reboot_code_buffer =
> page_address(image->control_code_page);
>  178
>  179            /* Prepare parameters for reboot_code_buffer*/
>  180            set_kernel_text_rw();
>  181            kexec_start_address = image->start;
> >182<           kexec_indirection_page = page_list;
>  183            kexec_mach_type = machine_arch_type;
>  184            kexec_boot_atags = image->arch.kernel_r2;
>  185
>  186            /* copy our kernel relocation code to the control code
> page */
>  187            reboot_entry = fncpy(reboot_code_buffer,

Can you please try the patch below:

diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index 963b5284d284..f86b3d17928e 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -571,7 +571,7 @@ static inline void section_update(unsigned long addr, pmdval_t mask,
{
pmd_t *pmd;

- pmd = pmd_off_k(addr);
+ pmd = pmd_offset(pud_offset(p4d_offset(pgd_offset(mm, addr), addr), addr), addr);

#ifdef CONFIG_ARM_LPAE
pmd[0] = __pmd((pmd_val(pmd[0]) & mask) | prot);

> > ...
>
> Best regards
> --
> Marek Szyprowski, PhD
> Samsung R&D Institute Poland
>

--
Sincerely yours,
Mike.