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From:   Vitaly Wool <vitaly.wool@konsulko.com>
Date:   Thu, 3 Jun 2021 17:51:25 +0200
Message-ID: <CAM4kBBKo2qzgfXZMk4Zfkw-wgMnwNRcdj_ZCJHg4=JAG0kb9oQ@mail.gmail.com>
Subject: Re: [PATCH v3 1/3] riscv: Factorize xip and !xip kernel address
 conversion macros
To:     Jisheng Zhang <jszhang3@mail.ustc.edu.cn>
Cc:     Alexandre Ghiti <alex@ghiti.fr>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Jisheng Zhang <jszhang@kernel.org>,
        Christoph Hellwig <hch@infradead.org>,
        Zong Li <zong.li@sifive.com>, Anup Patel <anup@brainfault.org>,
        linux-riscv <linux-riscv@lists.infradead.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Thu, Jun 3, 2021, 14:57 Jisheng Zhang <jszhang3@mail.ustc.edu.cn> wrote:
>
> On Thu, 3 Jun 2021 20:27:48 +0800
> Jisheng Zhang <jszhang3@mail.ustc.edu.cn> wrote:
>
> > On Thu,  3 Jun 2021 10:27:47 +0200
> > Alexandre Ghiti <alex@ghiti.fr> 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@ghiti.fr>
> > > ---
> > >  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) ?
> >
> > This CONFIG_PHYS_RAM_BASE is only available for XIP, could result in a
> > compiler error for !XIP?
> >
> > I'm also concerned with the unecessary overhead of kernel_mapping_pa_to_va()
> > for !XIP case, there's a "if" condition branch, and extra symbol: va_kernel_xip_pa_offset
>
> Err, I just found this symobl always exists no matter XIP is enabled or not.
> I will send out a patch for this clean up

What cleanup?

Best regards,
   Vitaly

>
> >
> > >             (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);       \
> > >     })
> >
> > Similar as kernel_mapping_pa_to_va(), an overhead of "if" condition branch
> > for !XIP and extra va_kernel_xip_pa_offset symbol.
> >
> > > -#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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