linux-kernel - Re: [PATCH] ARM: suspend: use flush range instead of flush all

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 12 Sep 2012 13:13:33 +0530
From:	"Shilimkar, Santosh" <santosh.shilimkar@...com>
To:	wzch <wzch@...vell.com>
Cc:	Russell King <linux@....linux.org.uk>,
	Dave Martin <dave.martin@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Subject: Re: [PATCH] ARM: suspend: use flush range instead of flush all

+ Lorenzo,

On Wed, Sep 12, 2012 at 12:48 PM, wzch <wzch@...vell.com> wrote:
> From: Wenzeng Chen <wzch@...vell.com>
>
> In cpu suspend function __cpu_suspend_save(), we save cp15 registers,
> resume function, sp and suspend_pgd, then flush the data to DDR, but
> no need to flush all D cache, only need to flush range.
>
> Change-Id: I591a1fde929f3f987c69306b601843ed975d3e41
You should drop above.

> Signed-off-by: Wenzeng Chen <wzch@...vell.com>
> ---
Lorenzo and myself discussed about the above expensive flush and he
is planning to post a similar patch but with small difference.

>  arch/arm/kernel/suspend.c |    4 +++-
>  1 files changed, 3 insertions(+), 1 deletions(-)
>
> diff --git a/arch/arm/kernel/suspend.c b/arch/arm/kernel/suspend.c
> index 1794cc3..bb582d8 100644
> --- a/arch/arm/kernel/suspend.c
> +++ b/arch/arm/kernel/suspend.c
> @@ -17,6 +17,7 @@ extern void cpu_resume_mmu(void);
>   */
>  void __cpu_suspend_save(u32 *ptr, u32 ptrsz, u32 sp, u32 *save_ptr)
>  {
> +       u32 *ptr_orig = ptr;
>         *save_ptr = virt_to_phys(ptr);
>
>         /* This must correspond to the LDM in cpu_resume() assembly */
> @@ -26,7 +27,8 @@ void __cpu_suspend_save(u32 *ptr, u32 ptrsz, u32 sp, u32 *save_ptr)
>
>         cpu_do_suspend(ptr);
>
> -       flush_cache_all();
Lorenzo's patch was limiting above flush to local cache (LOUs) instead
of dropping
it completely.

> +       __cpuc_flush_dcache_area((void *)ptr_orig, ptrsz);
> +       __cpuc_flush_dcache_area((void *)save_ptr, sizeof(*save_ptr));
>         outer_clean_range(*save_ptr, *save_ptr + ptrsz);
>         outer_clean_range(virt_to_phys(save_ptr),
>                           virt_to_phys(save_ptr) + sizeof(*save_ptr));

Just thinking bit more, even in case we drop the flush_cache_all()
completely, it should be safe since the suspend_finisher()  takes
care of the cache maintenance already.

Regards
Santosh
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/