Re: [Minios-devel] [PATCH v3 08/43] arm64: fix the wrong mask for to_virt/to_phys

[Huang Shijie <shijie.huang@xxxxxxx>]

On Thu, Apr 19, 2018 at 11:09:30AM +0100, Julien Grall wrote:
> 
> 
> On 19/04/18 11:01, Huang Shijie wrote:
> >On Wed, Apr 18, 2018 at 05:42:37PM +0100, Julien Grall wrote:
> >>Hi,
> >>
> >>On 16/04/18 07:31, Huang Shijie wrote:
> >>>In the arm64, the mask 0xffffffff will truncate the value, and
> >>
> >>s/In the/On/
> >>
> >>>to_virt/to_phys will get wrong results.
> >>>
> >>>This patch fixes it.
> >>>
> >>>Signed-off-by: Huang Shijie <shijie.huang@xxxxxxx>
> >>>---
> >>>  include/arm/arch_mm.h | 4 ++--
> >>>  1 file changed, 2 insertions(+), 2 deletions(-)
> >>>
> >>>diff --git a/include/arm/arch_mm.h b/include/arm/arch_mm.h
> >>>index c66856c..f77a210 100644
> >>>--- a/include/arm/arch_mm.h
> >>>+++ b/include/arm/arch_mm.h
> >>>@@ -15,8 +15,8 @@ extern paddr_t physical_address_offset;
> >>>  #define DEF_PAGE_PROT     0
> >>>-#define to_phys(x)                 
> >>>(((paddr_t)(x)+physical_address_offset) & 0xffffffff)
> >>>-#define to_virt(x)                 ((void 
> >>>*)(((x)-physical_address_offset) & 0xffffffff))
> >>>+#define to_phys(x)                 
> >>>(((paddr_t)(x)+physical_address_offset) & (~0UL))
> >>
> >>While this looks good on arm64, for arm32 unsigned long is not going to be
> >>enough. So I think you want to use ~(paddr_t)0 to cover the 32-bit case.
> >Sorry, I do not understand your meaning... :(
> >Do we need to cover the arm32 here?
> 
> to_phys() and to_virt() are defined in generic arm headers. While 32-bit is
> not supported, it would be better to cover it as cast problem are really a
> pain to fix it afterwards.
Okay, I will use "~(paddr_t)0" for the to_phys...

> 
> But I just realized that mini-os only support 4G of RAM because it relies on
> mapping all the memory. Am I right?
I did not try big memory which is over 4G. But I think the mini-os can support 
memory
over 4G.
> 
> If so, the UL might be fine. Any opinions?
Dido, I will use "~(paddr_t)0" for the to_phys...

Thanks
Huang Shijie

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