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

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Date:   Fri, 8 May 2020 08:53:27 +0200
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     Mike Rapoport <rppt@...ux.ibm.com>
Cc:     Mike Rapoport <rppt@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Rich Felker <dalias@...c.org>, linux-ia64@...r.kernel.org,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        linux-sh@...r.kernel.org,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        linux-mm@...ck.org, Paul Mackerras <paulus@...ba.org>,
        linux-hexagon@...r.kernel.org, Will Deacon <will@...nel.org>,
        kvmarm@...ts.cs.columbia.edu, Jonas Bonn <jonas@...thpole.se>,
        linux-arch@...r.kernel.org, Brian Cain <bcain@...eaurora.org>,
        Marc Zyngier <maz@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Ley Foon Tan <ley.foon.tan@...el.com>,
        Catalin Marinas <catalin.marinas@....com>,
        uclinux-h8-devel@...ts.sourceforge.jp,
        Fenghua Yu <fenghua.yu@...el.com>,
        Arnd Bergmann <arnd@...db.de>, kvm-ppc@...r.kernel.org,
        Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
        openrisc@...ts.librecores.org, Stafford Horne <shorne@...il.com>,
        Guan Xuetao <gxt@....edu.cn>,
        linux-arm-kernel@...ts.infradead.org,
        Christophe Leroy <christophe.leroy@....fr>,
        Tony Luck <tony.luck@...el.com>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        linux-kernel@...r.kernel.org,
        Michael Ellerman <mpe@...erman.id.au>,
        nios2-dev@...ts.rocketboards.org, linuxppc-dev@...ts.ozlabs.org,
        Łukasz Stelmach <l.stelmach@...sung.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [PATCH v4 02/14] arm: add support for folded p4d page tables

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@...ux.ibm.com>
>>>
>>> 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@...ux.ibm.com>
>> 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,

 > ...

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