[RFT PATCH] ARM: suspend: switch to swapper_pg_dir before using the vmap'ed stack

[RFT PATCH] ARM: suspend: switch to swapper_pg_dir before using the vmap'ed stack

[Ard Biesheuvel]

The resume from suspend code switches to the ID map so it can enable the
MMU. On !LPAE configurations, the ID map carries its own copy of the
kernel VA range, but this is not kept in sync with swapper_pg_dir, and
so it may lack the mapping of the kernel mode stack if CONFIG_VMAP_STACK
is enabled.

So let's switch to swapper_pg_dir right after re-enabling the MMU on
such configurations. This avoids a crash on resume observed on various
platforms [0].

[0] https://lore.kernel.org/linux-arm-kernel/20211122092816.2865873-8-ardb@kernel.org/

Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
Please test with the Kconfig patch [9177/1] reverted.

 arch/arm/kernel/sleep.S | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/arm/kernel/sleep.S b/arch/arm/kernel/sleep.S
index b062b3738bc6..6217ef90feb0 100644
--- a/arch/arm/kernel/sleep.S
+++ b/arch/arm/kernel/sleep.S
@@ -119,6 +119,13 @@ ENTRY(cpu_resume_mmu)
 ENDPROC(cpu_resume_mmu)
 	.popsection
 cpu_resume_after_mmu:
+#if defined(CONFIG_VMAP_STACK) && !defined(CONFIG_ARM_LPAE)
+	@ Before using the vmap'ed stack, we have to switch to swapper_pg_dir
+	@ as the ID map does not cover the vmalloc region.
+	mrc	p15, 0, ip, c2, c0, 1	@ read TTBR1
+	mcr	p15, 0, ip, c2, c0, 0	@ set TTBR0
+	isb
+#endif
 	bl	cpu_init		@ restore the und/abt/irq banked regs
 	mov	r0, #0			@ return zero on success
 	ldmfd	sp!, {r4 - r11, pc}
-- 
2.30.2


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Re: [RFT PATCH] ARM: suspend: switch to swapper_pg_dir before using the vmap'ed stack

[Geert Uytterhoeven]

Hi Ard,

On Thu, Jan 6, 2022 at 8:27 PM Ard Biesheuvel <ardb@kernel.org> wrote:
> The resume from suspend code switches to the ID map so it can enable the
> MMU. On !LPAE configurations, the ID map carries its own copy of the
> kernel VA range, but this is not kept in sync with swapper_pg_dir, and
> so it may lack the mapping of the kernel mode stack if CONFIG_VMAP_STACK
> is enabled.
>
> So let's switch to swapper_pg_dir right after re-enabling the MMU on
> such configurations. This avoids a crash on resume observed on various
> platforms [0].
>
> [0] https://lore.kernel.org/linux-arm-kernel/20211122092816.2865873-8-ardb@kernel.org/
>
> Cc: Marek Szyprowski <m.szyprowski@samsung.com>
> Cc: Geert Uytterhoeven <geert@linux-m68k.org>
> Cc: Jon Hunter <jonathanh@nvidia.com>
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Thanks for your patch!

This fixes s2ram on r8a7791/koelsch (dual Cortex-A15) with
shmobile_defconfig.
S2ram on sh73a0/kzm9g (dual Cortex-A9) works as before.

Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>

> ---
> Please test with the Kconfig patch [9177/1] reverted.
>
>  arch/arm/kernel/sleep.S | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/arch/arm/kernel/sleep.S b/arch/arm/kernel/sleep.S
> index b062b3738bc6..6217ef90feb0 100644
> --- a/arch/arm/kernel/sleep.S
> +++ b/arch/arm/kernel/sleep.S
> @@ -119,6 +119,13 @@ ENTRY(cpu_resume_mmu)
>  ENDPROC(cpu_resume_mmu)
>         .popsection
>  cpu_resume_after_mmu:
> +#if defined(CONFIG_VMAP_STACK) && !defined(CONFIG_ARM_LPAE)
> +       @ Before using the vmap'ed stack, we have to switch to swapper_pg_dir
> +       @ as the ID map does not cover the vmalloc region.
> +       mrc     p15, 0, ip, c2, c0, 1   @ read TTBR1
> +       mcr     p15, 0, ip, c2, c0, 0   @ set TTBR0
> +       isb
> +#endif
>         bl      cpu_init                @ restore the und/abt/irq banked regs
>         mov     r0, #0                  @ return zero on success
>         ldmfd   sp!, {r4 - r11, pc}

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

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Re: [RFT PATCH] ARM: suspend: switch to swapper_pg_dir before using the vmap'ed stack

[Ard Biesheuvel]

On Fri, 7 Jan 2022 at 10:15, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>
> Hi Ard,
>
> On Thu, Jan 6, 2022 at 8:27 PM Ard Biesheuvel <ardb@kernel.org> wrote:
> > The resume from suspend code switches to the ID map so it can enable the
> > MMU. On !LPAE configurations, the ID map carries its own copy of the
> > kernel VA range, but this is not kept in sync with swapper_pg_dir, and
> > so it may lack the mapping of the kernel mode stack if CONFIG_VMAP_STACK
> > is enabled.
> >
> > So let's switch to swapper_pg_dir right after re-enabling the MMU on
> > such configurations. This avoids a crash on resume observed on various
> > platforms [0].
> >
> > [0] https://lore.kernel.org/linux-arm-kernel/20211122092816.2865873-8-ardb@kernel.org/
> >
> > Cc: Marek Szyprowski <m.szyprowski@samsung.com>
> > Cc: Geert Uytterhoeven <geert@linux-m68k.org>
> > Cc: Jon Hunter <jonathanh@nvidia.com>
> > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
>
> Thanks for your patch!
>
> This fixes s2ram on r8a7791/koelsch (dual Cortex-A15) with
> shmobile_defconfig.
> S2ram on sh73a0/kzm9g (dual Cortex-A9) works as before.
>
> Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
>

Thanks Geert.

> > ---
> > Please test with the Kconfig patch [9177/1] reverted.
> >
> >  arch/arm/kernel/sleep.S | 7 +++++++
> >  1 file changed, 7 insertions(+)
> >
> > diff --git a/arch/arm/kernel/sleep.S b/arch/arm/kernel/sleep.S
> > index b062b3738bc6..6217ef90feb0 100644
> > --- a/arch/arm/kernel/sleep.S
> > +++ b/arch/arm/kernel/sleep.S
> > @@ -119,6 +119,13 @@ ENTRY(cpu_resume_mmu)
> >  ENDPROC(cpu_resume_mmu)
> >         .popsection
> >  cpu_resume_after_mmu:
> > +#if defined(CONFIG_VMAP_STACK) && !defined(CONFIG_ARM_LPAE)
> > +       @ Before using the vmap'ed stack, we have to switch to swapper_pg_dir
> > +       @ as the ID map does not cover the vmalloc region.
> > +       mrc     p15, 0, ip, c2, c0, 1   @ read TTBR1
> > +       mcr     p15, 0, ip, c2, c0, 0   @ set TTBR0
> > +       isb
> > +#endif
> >         bl      cpu_init                @ restore the und/abt/irq banked regs
> >         mov     r0, #0                  @ return zero on success
> >         ldmfd   sp!, {r4 - r11, pc}
>
> Gr{oetje,eeting}s,
>
>                         Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds

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Re: [RFT PATCH] ARM: suspend: switch to swapper_pg_dir before using the vmap'ed stack

[Marek Szyprowski]

Hi Ard,

On 06.01.2022 20:26, Ard Biesheuvel wrote:
> The resume from suspend code switches to the ID map so it can enable the
> MMU. On !LPAE configurations, the ID map carries its own copy of the
> kernel VA range, but this is not kept in sync with swapper_pg_dir, and
> so it may lack the mapping of the kernel mode stack if CONFIG_VMAP_STACK
> is enabled.
>
> So let's switch to swapper_pg_dir right after re-enabling the MMU on
> such configurations. This avoids a crash on resume observed on various
> platforms [0].
>
> [0] https://protect2.fireeye.com/v1/url?k=efa2c314-b039fa16-efa3485b-0cc47a31381a-5dcf992b5d854429&q=1&e=1dac5900-a7aa-40ed-a2f0-9af17ae05bfe&u=https%3A%2F%2Flore.kernel.org%2Flinux-arm-kernel%2F20211122092816.2865873-8-ardb%40kernel.org%2F
>
> Cc: Marek Szyprowski <m.szyprowski@samsung.com>
> Cc: Geert Uytterhoeven <geert@linux-m68k.org>
> Cc: Jon Hunter <jonathanh@nvidia.com>
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

This fixes the suspend/resume issue observed on ARM 32bit Exynos based 
boards. Thanks!

Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>

Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>

> ---
> Please test with the Kconfig patch [9177/1] reverted.
>
>   arch/arm/kernel/sleep.S | 7 +++++++
>   1 file changed, 7 insertions(+)
>
> diff --git a/arch/arm/kernel/sleep.S b/arch/arm/kernel/sleep.S
> index b062b3738bc6..6217ef90feb0 100644
> --- a/arch/arm/kernel/sleep.S
> +++ b/arch/arm/kernel/sleep.S
> @@ -119,6 +119,13 @@ ENTRY(cpu_resume_mmu)
>   ENDPROC(cpu_resume_mmu)
>   	.popsection
>   cpu_resume_after_mmu:
> +#if defined(CONFIG_VMAP_STACK) && !defined(CONFIG_ARM_LPAE)
> +	@ Before using the vmap'ed stack, we have to switch to swapper_pg_dir
> +	@ as the ID map does not cover the vmalloc region.
> +	mrc	p15, 0, ip, c2, c0, 1	@ read TTBR1
> +	mcr	p15, 0, ip, c2, c0, 0	@ set TTBR0
> +	isb
> +#endif
>   	bl	cpu_init		@ restore the und/abt/irq banked regs
>   	mov	r0, #0			@ return zero on success
>   	ldmfd	sp!, {r4 - r11, pc}

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


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Re: [RFT PATCH] ARM: suspend: switch to swapper_pg_dir before using the vmap'ed stack

[Ard Biesheuvel]

On Mon, 10 Jan 2022 at 10:36, Marek Szyprowski <m.szyprowski@samsung.com> wrote:
>
> Hi Ard,
>
> On 06.01.2022 20:26, Ard Biesheuvel wrote:
> > The resume from suspend code switches to the ID map so it can enable the
> > MMU. On !LPAE configurations, the ID map carries its own copy of the
> > kernel VA range, but this is not kept in sync with swapper_pg_dir, and
> > so it may lack the mapping of the kernel mode stack if CONFIG_VMAP_STACK
> > is enabled.
> >
> > So let's switch to swapper_pg_dir right after re-enabling the MMU on
> > such configurations. This avoids a crash on resume observed on various
> > platforms [0].
> >
> > [0] https://protect2.fireeye.com/v1/url?k=efa2c314-b039fa16-efa3485b-0cc47a31381a-5dcf992b5d854429&q=1&e=1dac5900-a7aa-40ed-a2f0-9af17ae05bfe&u=https%3A%2F%2Flore.kernel.org%2Flinux-arm-kernel%2F20211122092816.2865873-8-ardb%40kernel.org%2F
> >
> > Cc: Marek Szyprowski <m.szyprowski@samsung.com>
> > Cc: Geert Uytterhoeven <geert@linux-m68k.org>
> > Cc: Jon Hunter <jonathanh@nvidia.com>
> > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
>
> This fixes the suspend/resume issue observed on ARM 32bit Exynos based
> boards. Thanks!
>
> Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
>
> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
>

Thanks Marek.

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