Messages in this thread | | | Date | Thu, 3 Jun 2021 23:16:56 +0800 | From | Jisheng Zhang <> | Subject | Re: [PATCH v3 1/3] riscv: Factorize xip and !xip kernel address conversion macros |
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On Thu, 3 Jun 2021 17:06:39 +0200 Alex Ghiti <alex@ghiti.fr> wrote:
> Le 3/06/2021 à 15:53, Jisheng Zhang a écrit : > > On Thu, 3 Jun 2021 18:46:47 +0530 > > Anup Patel <anup@brainfault.org> wrote: > > > >> On Thu, Jun 3, 2021 at 6:27 PM Alex Ghiti <alex@ghiti.fr> wrote: > >>> > >>> Hi Jisheng, > > > > Hi, > > > >>> > >>> Le 3/06/2021 à 14:27, Jisheng Zhang a écrit : > >>>> 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? > >>> > >>> You're right, I have this patch in my branch and forgot to squash it > >>> > >>>> > >>>> 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 > >>> > >>> I understand your concerns even if I don't find that the overhead is > >>> that important here, I prefer the readability improvement. I can always > > > > For readability, we still can avoid introducing va_kernel_xip_pa_offset > > symbol by simply define va_kernel_xip_pa_offset as 0 if XIP as you did > > for XIP_OFFSET > > > > PS: this may need a preparation patch: > > http://lists.infradead.org/pipermail/linux-riscv/2021-June/006802.html > > IIUC, that won't improve readability, just avoid to allocate > va_kernel_xip_pa_offset in !XIP kernel right?
I mean even we can improve code readability while still avoid the va_kernel_xip_pa_offset symbol for !XIP case. Probably it's implemented as you did for XIP_OFFSET:
#ifdef CONFIG_XIP_KERNEL extern unsigned long va_kernel_xip_pa_offset; #else #define va_kernel_xip_pa_offset 0 #endif
But since currently va_kernel_xip_pa_offset always exisits no matter XIP is enabled or not, so you may need the preparation patch to clean up, otherwise there may be compiler error. > > > > >>> add unlikely/likely builtin to improve things or completely remove this > >>> patch if others agree with you. > >> > >> I would also prefer readable code for long-term maintainability. Currently, > >> the nested "#ifdefs" are increasing causing developers to easily break > >> untested combinations. > >> > >> Regards, > >> Anup > >> > >>> > >>> Thanks, > >>> > >>> Alex > >>> > >>>> > >>>>> (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__ > >>>> > >>>> > >>>> > >>>> _______________________________________________ > >>>> linux-riscv mailing list > >>>> linux-riscv@lists.infradead.org > >>>> http://lists.infradead.org/mailman/listinfo/linux-riscv > >>>> > > > > > > > > _______________________________________________ > > linux-riscv mailing list > > linux-riscv@lists.infradead.org > > http://lists.infradead.org/mailman/listinfo/linux-riscv > >
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