linux-kernel - Re: [PATCH v3 1/3] riscv: Factorize xip and !xip kernel address conversion macros

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Message-ID: <20210603234950.3ff475e3@xhacker>
Date:   Thu, 3 Jun 2021 23:49:50 +0800
From:   Jisheng Zhang <jszhang3@...l.ustc.edu.cn>
To:     Vitaly Wool <vitaly.wool@...sulko.com>
Cc:     Alexandre Ghiti <alex@...ti.fr>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Jisheng Zhang <jszhang@...nel.org>,
        Christoph Hellwig <hch@...radead.org>,
        Zong Li <zong.li@...ive.com>, Anup Patel <anup@...infault.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/3] riscv: Factorize xip and !xip kernel address
 conversion macros

On Thu, 3 Jun 2021 17:51:25 +0200
Vitaly Wool <vitaly.wool@...sulko.com> wrote:

> On Thu, Jun 3, 2021, 14:57 Jisheng Zhang <jszhang3@...l.ustc.edu.cn> wrote:
> >
> > On Thu, 3 Jun 2021 20:27:48 +0800
> > Jisheng Zhang <jszhang3@...l.ustc.edu.cn> wrote:
> >  
> > > On Thu,  3 Jun 2021 10:27:47 +0200
> > > Alexandre Ghiti <alex@...ti.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@...ti.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?
> 

http://lists.infradead.org/pipermail/linux-riscv/2021-June/006802.html