Re: [PATCH v4 2/4] riscv: Simplify xip and !xip kernel address conversion macros

[Alex Ghiti]

Le 4/06/2021 à 14:47, Jisheng Zhang a écrit :
> Hi Alexandre,
>
> On Fri,  4 Jun 2021 13:49:48 +0200
> Alexandre Ghiti <alex@xxxxxxxx> wrote:
>
> > To simplify the kernel address conversion code, make the same definition of
> > kernel_mapping_pa_to_va and kernel_mapping_va_to_pa compatible for both xip
> > and !xip kernel by defining XIP_OFFSET to 0 in !xip kernel.
> >
> > Signed-off-by: Alexandre Ghiti <alex@xxxxxxxx>
> > Reviewed-by: Anup Patel <anup@xxxxxxxxxxxxxx>
> > ---
> >   arch/riscv/include/asm/page.h    | 14 +++-----------
> >   arch/riscv/include/asm/pgtable.h |  2 ++
> >   2 files changed, 5 insertions(+), 11 deletions(-)
> >
> > diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h
> > index 6a7761c86ec2..6e004d8fda4d 100644
> > --- a/arch/riscv/include/asm/page.h
> > +++ b/arch/riscv/include/asm/page.h
> > @@ -93,9 +93,7 @@ extern unsigned long va_pa_offset;
> >   #ifdef CONFIG_64BIT
> >   extern unsigned long va_kernel_pa_offset;
> >   #endif
> > -#ifdef CONFIG_XIP_KERNEL
> >   extern unsigned long va_kernel_xip_pa_offset;
> > -#endif
> >   extern unsigned long pfn_base;
> >   #define ARCH_PFN_OFFSET		(pfn_base)
> >   #else
> > @@ -103,6 +101,7 @@ extern unsigned long pfn_base;
> >   #ifdef CONFIG_64BIT
> >   #define va_kernel_pa_offset	0
> >   #endif
> > +#define va_kernel_xip_pa_offset 0
> >   #define ARCH_PFN_OFFSET		(PAGE_OFFSET >> PAGE_SHIFT)
> >   #endif /* CONFIG_MMU */
> >   
> > @@ -110,29 +109,22 @@ extern unsigned long kernel_virt_addr;
> >   
> >   #ifdef CONFIG_64BIT
> >   #define linear_mapping_pa_to_va(x)	((void *)((unsigned long)(x) + va_pa_offset))
> > -#ifdef CONFIG_XIP_KERNEL
> >   #define kernel_mapping_pa_to_va(y)	({						\
> >   	unsigned long _y = y;								\
> >   	(_y >= CONFIG_PHYS_RAM_BASE) ?							\
>
> For !XIP, IIRC, one rule for riscv kernel is one unified Image for all RV64GC
> or RV32GC platforms. When CONFIG_PHYS_RAM_BASE is available for all
> riscv platforms after patch1, I'm not sure the common unified Image is still
> possible or not.

I completely did not handle the 32b case and was convinced that 
0x8000_0000 was indeed the beginning of the RAM for all riscv64 plaforms.

> One possible solution would be forcing CONFIG_PHYS_RAM_BASE = 0 if !XIP in patch1
> or remove patch1 instead define CONFIG_PHY_RAM_BASE 0 for !XIP

Setting CONFIG_PHYS_RAM_BASE to 0 for !xip kernels is IMO not that great 
since it represents something that is real but wrong (unlike XIP_OFFSET 
which is 0 for !xip kernel and in that case, this is true). I will think 
to a better solution and am open to suggestions.

Thanks Jisheng again for your reviews, really appreciated!

Alex

> Thanks
>
> >   		(void *)((unsigned long)(_y) + va_kernel_pa_offset + XIP_OFFSET) :	\
> >   		(void *)((unsigned long)(_y) + va_kernel_xip_pa_offset);		\
> >   	})
> > -#else
> > -#define kernel_mapping_pa_to_va(x)	((void *)((unsigned long)(x) + va_kernel_pa_offset))
> > -#endif
> >   #define __pa_to_va_nodebug(x)		linear_mapping_pa_to_va(x)
> >   
> >   #define linear_mapping_va_to_pa(x)	((unsigned long)(x) - va_pa_offset)
> > -#ifdef CONFIG_XIP_KERNEL
> >   #define kernel_mapping_va_to_pa(y) ({						\
> >   	unsigned long _y = y;							\
> >   	(_y < kernel_virt_addr + XIP_OFFSET) ?					\
> >   		((unsigned long)(_y) - va_kernel_xip_pa_offset) :		\
> >   		((unsigned long)(_y) - va_kernel_pa_offset - XIP_OFFSET);	\
> >   	})
> > -#else
> > -#define kernel_mapping_va_to_pa(x)	((unsigned long)(x) - va_kernel_pa_offset)
> > -#endif
> > +
> >   #define __va_to_pa_nodebug(x)	({						\
> >   	unsigned long _x = x;							\
> >   	(_x < kernel_virt_addr) ?						\
> > @@ -141,7 +133,7 @@ extern unsigned long kernel_virt_addr;
> >   #else
> >   #define __pa_to_va_nodebug(x)  ((void *)((unsigned long) (x) + va_pa_offset))
> >   #define __va_to_pa_nodebug(x)  ((unsigned long)(x) - va_pa_offset)
> > -#endif
> > +#endif /* CONFIG_64BIT */
> >   
> >   #ifdef CONFIG_DEBUG_VIRTUAL
> >   extern phys_addr_t __virt_to_phys(unsigned long x);
> > diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> > index bde8ce3bfe7c..d98e931a31e5 100644
> > --- a/arch/riscv/include/asm/pgtable.h
> > +++ b/arch/riscv/include/asm/pgtable.h
> > @@ -77,6 +77,8 @@
> >   
> >   #ifdef CONFIG_XIP_KERNEL
> >   #define XIP_OFFSET		SZ_8M
> > +#else
> > +#define XIP_OFFSET		0
> >   #endif
> >   
> >   #ifndef __ASSEMBLY__
>
>
>
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