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

From: Mike Rapoport <[email-masked]>
Date: Fri, 8 May 2020 20:42:32 +0300

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 <[email-masked]>
> >>>
> >>> 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 <[email-masked]>
> >> 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.

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