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Date: Wed, 28 Feb 2018 21:45:25 -0500
From: Woody Suwalski <terraluna977@...il.com>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: Linux Kernel List <linux-kernel@...r.kernel.org>,
the arch/x86 maintainers <x86@...nel.org>,
William Grant <william.grant@...onical.com>
Subject: Re: 4.16 regression: s2ram broken on non-PAE i686
Thomas Gleixner wrote:
> Woody,
>
> On Wed, 28 Feb 2018, Woody Suwalski wrote:
>> Certainly. I understand you want dmesg output for kernels build with and
>> without PAE, not just PAE=n on the cmdline :-)
>> Here it is...
> Thanks for providing the data. It did not pinpoint the issue but at least
> it gave me the hint to look into the right direction.
>
> Does the patch below fix the issue for you? It's untested as I'm at home
> and have no access to a 32bit machine right now.
>
> Thanks,
>
> tglx
>
> 8<------------------
> Subject: x86/cpu_entry_area: Sync cpu_entry_area to initial_page_table
> From: Thomas Gleixner <tglx@...utronix.de>
> Date: Wed, 28 Feb 2018 21:14:26 +0100
>
> The separation of the cpu_entry_area from the fixmap missed the fact that
> on 32bit non-PAE kernels the cpu_entry_area mapping might not be covered in
> initial_page_table by the previous synchronizations.
>
> This results in suspend/resume failures because 32bit utilizes initial page
> table for resume. The absence of the cpu_entry_area mapping results in a
> triple fault, aka. insta reboot.
>
> Synchronize the initial page table after setting up the cpu entry
> area. Instead of adding yet another copy of the same code, move it to a
> function and invoke it from the various places.
>
> It needs to be investigated if the existing calls in setup_arch() and
> setup_per_cpu_areas() can be replaced by the later invocation from
> setup_cpu_entry_areas(), but that's beyond the scope of this fix.
>
> Fixes: 92a0f81d8957 ("x86/cpu_entry_area: Move it out of the fixmap")
> Reported-by: Woody Suwalski <terraluna977@...il.com>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> Cc: stable@...r.kernel.org
> ---
> arch/x86/include/asm/pgtable_32.h | 1 +
> arch/x86/include/asm/pgtable_64.h | 1 +
> arch/x86/kernel/setup.c | 17 +++++------------
> arch/x86/kernel/setup_percpu.c | 17 ++++-------------
> arch/x86/mm/cpu_entry_area.c | 6 ++++++
> arch/x86/mm/init_32.c | 15 +++++++++++++++
> 6 files changed, 32 insertions(+), 25 deletions(-)
>
> --- a/arch/x86/include/asm/pgtable_32.h
> +++ b/arch/x86/include/asm/pgtable_32.h
> @@ -32,6 +32,7 @@ extern pmd_t initial_pg_pmd[];
> static inline void pgtable_cache_init(void) { }
> static inline void check_pgt_cache(void) { }
> void paging_init(void);
> +void sync_initial_page_table(void);
>
> /*
> * Define this if things work differently on an i386 and an i486:
> --- a/arch/x86/include/asm/pgtable_64.h
> +++ b/arch/x86/include/asm/pgtable_64.h
> @@ -28,6 +28,7 @@ extern pgd_t init_top_pgt[];
> #define swapper_pg_dir init_top_pgt
>
> extern void paging_init(void);
> +static inline void sync_initial_page_table(void) { }
>
> #define pte_ERROR(e) \
> pr_err("%s:%d: bad pte %p(%016lx)\n", \
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -1204,20 +1204,13 @@ void __init setup_arch(char **cmdline_p)
>
> kasan_init();
>
> -#ifdef CONFIG_X86_32
> - /* sync back kernel address range */
> - clone_pgd_range(initial_page_table + KERNEL_PGD_BOUNDARY,
> - swapper_pg_dir + KERNEL_PGD_BOUNDARY,
> - KERNEL_PGD_PTRS);
> -
> /*
> - * sync back low identity map too. It is used for example
> - * in the 32-bit EFI stub.
> + * Sync back kernel address range.
> + *
> + * FIXME: Can the later sync in setup_cpu_entry_areas() replace
> + * this call?
> */
> - clone_pgd_range(initial_page_table,
> - swapper_pg_dir + KERNEL_PGD_BOUNDARY,
> - min(KERNEL_PGD_PTRS, KERNEL_PGD_BOUNDARY));
> -#endif
> + sync_initial_page_table();
>
> tboot_probe();
>
> --- a/arch/x86/kernel/setup_percpu.c
> +++ b/arch/x86/kernel/setup_percpu.c
> @@ -287,24 +287,15 @@ void __init setup_per_cpu_areas(void)
> /* Setup cpu initialized, callin, callout masks */
> setup_cpu_local_masks();
>
> -#ifdef CONFIG_X86_32
> /*
> * Sync back kernel address range again. We already did this in
> * setup_arch(), but percpu data also needs to be available in
> * the smpboot asm. We can't reliably pick up percpu mappings
> * using vmalloc_fault(), because exception dispatch needs
> * percpu data.
> + *
> + * FIXME: Can the later sync in setup_cpu_entry_areas() replace
> + * this call?
> */
> - clone_pgd_range(initial_page_table + KERNEL_PGD_BOUNDARY,
> - swapper_pg_dir + KERNEL_PGD_BOUNDARY,
> - KERNEL_PGD_PTRS);
> -
> - /*
> - * sync back low identity map too. It is used for example
> - * in the 32-bit EFI stub.
> - */
> - clone_pgd_range(initial_page_table,
> - swapper_pg_dir + KERNEL_PGD_BOUNDARY,
> - min(KERNEL_PGD_PTRS, KERNEL_PGD_BOUNDARY));
> -#endif
> + sync_initial_page_table();
> }
> --- a/arch/x86/mm/cpu_entry_area.c
> +++ b/arch/x86/mm/cpu_entry_area.c
> @@ -163,4 +163,10 @@ void __init setup_cpu_entry_areas(void)
>
> for_each_possible_cpu(cpu)
> setup_cpu_entry_area(cpu);
> +
> + /*
> + * This is the last essential update to swapper_pgdir which needs
> + * to be synchronized to initial_page_table on 32bit.
> + */
> + sync_initial_page_table();
> }
> --- a/arch/x86/mm/init_32.c
> +++ b/arch/x86/mm/init_32.c
> @@ -453,6 +453,21 @@ static inline void permanent_kmaps_init(
> }
> #endif /* CONFIG_HIGHMEM */
>
> +void __init sync_initial_page_table(void)
> +{
> + clone_pgd_range(initial_page_table + KERNEL_PGD_BOUNDARY,
> + swapper_pg_dir + KERNEL_PGD_BOUNDARY,
> + KERNEL_PGD_PTRS);
> +
> + /*
> + * sync back low identity map too. It is used for example
> + * in the 32-bit EFI stub.
> + */
> + clone_pgd_range(initial_page_table,
> + swapper_pg_dir + KERNEL_PGD_BOUNDARY,
> + min(KERNEL_PGD_PTRS, KERNEL_PGD_BOUNDARY));
> +}
> +
> void __init native_pagetable_init(void)
> {
> unsigned long pfn, va;
Thanks for the patch, good news, it did fix the problem.
I did 2 builds and both worked OK over the s2ram cycle.
It will be necessary to add the patch to 4.15-stable and 4.14-stable, I
believe that both have now broken s2ram.
I will build tomorrow 4.15 and 4.14 with your patch and try it out - the
patch seems to apply OK to 4.15.7 and 4.14.23...
Thanks, Woody
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