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

On Fri, May 08, 2020 at 08:53:27AM +0200, Marek Szyprowski wrote:

quoted

On 07.05.2020 18:11, Mike Rapoport wrote:

quoted

On Thu, May 07, 2020 at 02:16:56PM +0200, Marek Szyprowski wrote:

quoted

On 14.04.2020 17:34, Mike Rapoport wrote:

quoted

From: Mike Rapoport <redacted>

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 <redacted>

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);