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SubjectRE: [PATCH v2 3/6] powerpc: Convert flush_icache_range & friends to C
On Tue, 2019-09-03 at 08:08 +0200, Christophe Leroy wrote:
>
> Le 03/09/2019 à 07:23, Alastair D'Silva a écrit :
> > From: Alastair D'Silva <alastair@d-silva.org>
> >
> > Similar to commit 22e9c88d486a
> > ("powerpc/64: reuse PPC32 static inline flush_dcache_range()")
> > this patch converts the following ASM symbols to C:
> > flush_icache_range()
> > __flush_dcache_icache()
> > __flush_dcache_icache_phys()
> >
> > This was done as we discovered a long-standing bug where the length
> > of the
> > range was truncated due to using a 32 bit shift instead of a 64 bit
> > one.
> >
> > By converting these functions to C, it becomes easier to maintain.
> >
> > flush_dcache_icache_phys() retains a critical assembler section as
> > we must
> > ensure there are no memory accesses while the data MMU is disabled
> > (authored by Christophe Leroy). Since this has no external callers,
> > it has
> > also been made static, allowing the compiler to inline it within
> > flush_dcache_icache_page().
> >
> > Signed-off-by: Alastair D'Silva <alastair@d-silva.org>
> > Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> > ---
> > arch/powerpc/include/asm/cache.h | 26 ++---
> > arch/powerpc/include/asm/cacheflush.h | 24 ++--
> > arch/powerpc/kernel/misc_32.S | 117 --------------------
> > arch/powerpc/kernel/misc_64.S | 102 -----------------
> > arch/powerpc/mm/mem.c | 152
> > +++++++++++++++++++++++++-
> > 5 files changed, 173 insertions(+), 248 deletions(-)
> >
> > diff --git a/arch/powerpc/include/asm/cache.h
> > b/arch/powerpc/include/asm/cache.h
> > index f852d5cd746c..91c808c6738b 100644
> > --- a/arch/powerpc/include/asm/cache.h
> > +++ b/arch/powerpc/include/asm/cache.h
> > @@ -98,20 +98,7 @@ static inline u32 l1_icache_bytes(void)
> > #endif
> > #endif /* ! __ASSEMBLY__ */
> >
> > -#if defined(__ASSEMBLY__)
> > -/*
> > - * For a snooping icache, we still need a dummy icbi to purge all
> > the
> > - * prefetched instructions from the ifetch buffers. We also need a
> > sync
> > - * before the icbi to order the the actual stores to memory that
> > might
> > - * have modified instructions with the icbi.
> > - */
> > -#define PURGE_PREFETCHED_INS \
> > - sync; \
> > - icbi 0,r3; \
> > - sync; \
> > - isync
> > -
> > -#else
> > +#if !defined(__ASSEMBLY__)
> > #define __read_mostly
> > __attribute__((__section__(".data..read_mostly")))
> >
> > #ifdef CONFIG_PPC_BOOK3S_32
> > @@ -145,6 +132,17 @@ static inline void dcbst(void *addr)
> > {
> > __asm__ __volatile__ ("dcbst %y0" : : "Z"(*(u8 *)addr) :
> > "memory");
> > }
> > +
> > +static inline void icbi(void *addr)
> > +{
> > + __asm__ __volatile__ ("icbi 0, %0" : : "r"(addr) : "memory");
>
> I think "__asm__ __volatile__" is deprecated. Use "asm volatile"
> instead.
>

Ok.

> > +}
> > +
> > +static inline void iccci(void *addr)
> > +{
> > + __asm__ __volatile__ ("iccci 0, %0" : : "r"(addr) : "memory");
> > +}
> > +
>
> Same
>
> > #endif /* !__ASSEMBLY__ */
> > #endif /* __KERNEL__ */
> > #endif /* _ASM_POWERPC_CACHE_H */
> > diff --git a/arch/powerpc/include/asm/cacheflush.h
> > b/arch/powerpc/include/asm/cacheflush.h
> > index ed57843ef452..4a1c9f0200e1 100644
> > --- a/arch/powerpc/include/asm/cacheflush.h
> > +++ b/arch/powerpc/include/asm/cacheflush.h
> > @@ -42,24 +42,20 @@ extern void flush_dcache_page(struct page
> > *page);
> > #define flush_dcache_mmap_lock(mapping) do { } while
> > (0)
> > #define flush_dcache_mmap_unlock(mapping) do { } while (0)
> >
> > -extern void flush_icache_range(unsigned long, unsigned long);
> > +void flush_icache_range(unsigned long start, unsigned long stop);
> > extern void flush_icache_user_range(struct vm_area_struct *vma,
> > struct page *page, unsigned long
> > addr,
> > int len);
> > -extern void __flush_dcache_icache(void *page_va);
> > extern void flush_dcache_icache_page(struct page *page);
> > -#if defined(CONFIG_PPC32) && !defined(CONFIG_BOOKE)
> > -extern void __flush_dcache_icache_phys(unsigned long physaddr);
> > -#else
> > -static inline void __flush_dcache_icache_phys(unsigned long
> > physaddr)
> > -{
> > - BUG();
> > -}
> > -#endif
> > -
> > -/*
> > - * Write any modified data cache blocks out to memory and
> > invalidate them.
> > - * Does not invalidate the corresponding instruction cache blocks.
> > +void __flush_dcache_icache(void *page);
> > +
> > +/**
> > + * flush_dcache_range(): Write any modified data cache blocks out
> > to memory and
> > + * invalidate them. Does not invalidate the corresponding
> > instruction cache
> > + * blocks.
> > + *
> > + * @start: the start address
> > + * @stop: the stop address (exclusive)
> > */
> > static inline void flush_dcache_range(unsigned long start,
> > unsigned long stop)
> > {
> > diff --git a/arch/powerpc/kernel/misc_32.S
> > b/arch/powerpc/kernel/misc_32.S
> > index fe4bd321730e..12b95e6799d4 100644
> > --- a/arch/powerpc/kernel/misc_32.S
> > +++ b/arch/powerpc/kernel/misc_32.S
> > @@ -318,123 +318,6 @@
> > END_FTR_SECTION_IFSET(CPU_FTR_UNIFIED_ID_CACHE)
> > EXPORT_SYMBOL(flush_instruction_cache)
> > #endif /* CONFIG_PPC_8xx */
> >
> > -/*
> > - * Write any modified data cache blocks out to memory
> > - * and invalidate the corresponding instruction cache blocks.
> > - * This is a no-op on the 601.
> > - *
> > - * flush_icache_range(unsigned long start, unsigned long stop)
> > - */
> > -_GLOBAL(flush_icache_range)
> > -BEGIN_FTR_SECTION
> > - PURGE_PREFETCHED_INS
> > - blr /* for 601, do nothing */
> > -END_FTR_SECTION_IFSET(CPU_FTR_COHERENT_ICACHE)
> > - rlwinm r3,r3,0,0,31 - L1_CACHE_SHIFT
> > - subf r4,r3,r4
> > - addi r4,r4,L1_CACHE_BYTES - 1
> > - srwi. r4,r4,L1_CACHE_SHIFT
> > - beqlr
> > - mtctr r4
> > - mr r6,r3
> > -1: dcbst 0,r3
> > - addi r3,r3,L1_CACHE_BYTES
> > - bdnz 1b
> > - sync /* wait for dcbst's to get
> > to ram */
> > -#ifndef CONFIG_44x
> > - mtctr r4
> > -2: icbi 0,r6
> > - addi r6,r6,L1_CACHE_BYTES
> > - bdnz 2b
> > -#else
> > - /* Flash invalidate on 44x because we are passed kmapped
> > addresses and
> > - this doesn't work for userspace pages due to the virtually
> > tagged
> > - icache. Sigh. */
> > - iccci 0, r0
> > -#endif
> > - sync /* additional sync needed
> > on g4 */
> > - isync
> > - blr
> > -_ASM_NOKPROBE_SYMBOL(flush_icache_range)
> > -EXPORT_SYMBOL(flush_icache_range)
> > -
> > -/*
> > - * Flush a particular page from the data cache to RAM.
> > - * Note: this is necessary because the instruction cache does
> > *not*
> > - * snoop from the data cache.
> > - * This is a no-op on the 601 which has a unified cache.
> > - *
> > - * void __flush_dcache_icache(void *page)
> > - */
> > -_GLOBAL(__flush_dcache_icache)
> > -BEGIN_FTR_SECTION
> > - PURGE_PREFETCHED_INS
> > - blr
> > -END_FTR_SECTION_IFSET(CPU_FTR_COHERENT_ICACHE)
> > - rlwinm r3,r3,0,0,31-PAGE_SHIFT /* Get page base
> > address */
> > - li r4,PAGE_SIZE/L1_CACHE_BYTES /* Number of lines in a
> > page */
> > - mtctr r4
> > - mr r6,r3
> > -0: dcbst 0,r3 /* Write line to
> > ram */
> > - addi r3,r3,L1_CACHE_BYTES
> > - bdnz 0b
> > - sync
> > -#ifdef CONFIG_44x
> > - /* We don't flush the icache on 44x. Those have a virtual
> > icache
> > - * and we don't have access to the virtual address here (it's
> > - * not the page vaddr but where it's mapped in user space). The
> > - * flushing of the icache on these is handled elsewhere, when
> > - * a change in the address space occurs, before returning to
> > - * user space
> > - */
> > -BEGIN_MMU_FTR_SECTION
> > - blr
> > -END_MMU_FTR_SECTION_IFSET(MMU_FTR_TYPE_44x)
> > -#endif /* CONFIG_44x */
> > - mtctr r4
> > -1: icbi 0,r6
> > - addi r6,r6,L1_CACHE_BYTES
> > - bdnz 1b
> > - sync
> > - isync
> > - blr
> > -
> > -#ifndef CONFIG_BOOKE
> > -/*
> > - * Flush a particular page from the data cache to RAM, identified
> > - * by its physical address. We turn off the MMU so we can just
> > use
> > - * the physical address (this may be a highmem page without a
> > kernel
> > - * mapping).
> > - *
> > - * void __flush_dcache_icache_phys(unsigned long physaddr)
> > - */
> > -_GLOBAL(__flush_dcache_icache_phys)
> > -BEGIN_FTR_SECTION
> > - PURGE_PREFETCHED_INS
> > - blr /* for 601, do nothing */
> > -END_FTR_SECTION_IFSET(CPU_FTR_COHERENT_ICACHE)
> > - mfmsr r10
> > - rlwinm r0,r10,0,28,26 /* clear DR */
> > - mtmsr r0
> > - isync
> > - rlwinm r3,r3,0,0,31-PAGE_SHIFT /* Get page base
> > address */
> > - li r4,PAGE_SIZE/L1_CACHE_BYTES /* Number of lines in a
> > page */
> > - mtctr r4
> > - mr r6,r3
> > -0: dcbst 0,r3 /* Write line to
> > ram */
> > - addi r3,r3,L1_CACHE_BYTES
> > - bdnz 0b
> > - sync
> > - mtctr r4
> > -1: icbi 0,r6
> > - addi r6,r6,L1_CACHE_BYTES
> > - bdnz 1b
> > - sync
> > - mtmsr r10 /* restore DR */
> > - isync
> > - blr
> > -#endif /* CONFIG_BOOKE */
> > -
> > /*
> > * Copy a whole page. We use the dcbz instruction on the
> > destination
> > * to reduce memory traffic (it eliminates the unnecessary reads
> > of
> > diff --git a/arch/powerpc/kernel/misc_64.S
> > b/arch/powerpc/kernel/misc_64.S
> > index 9bc0aa9aeb65..ff20c253f273 100644
> > --- a/arch/powerpc/kernel/misc_64.S
> > +++ b/arch/powerpc/kernel/misc_64.S
> > @@ -49,108 +49,6 @@ _GLOBAL(call_do_irq)
> > mtlr r0
> > blr
> >
> > - .section ".toc","aw"
> > -PPC64_CACHES:
> > - .tc ppc64_caches[TC],ppc64_caches
> > - .section ".text"
> > -
> > -/*
> > - * Write any modified data cache blocks out to memory
> > - * and invalidate the corresponding instruction cache blocks.
> > - *
> > - * flush_icache_range(unsigned long start, unsigned long stop)
> > - *
> > - * flush all bytes from start through stop-1 inclusive
> > - */
> > -
> > -_GLOBAL_TOC(flush_icache_range)
> > -BEGIN_FTR_SECTION
> > - PURGE_PREFETCHED_INS
> > - blr
> > -END_FTR_SECTION_IFSET(CPU_FTR_COHERENT_ICACHE)
> > -/*
> > - * Flush the data cache to memory
> > - *
> > - * Different systems have different cache line sizes
> > - * and in some cases i-cache and d-cache line sizes differ from
> > - * each other.
> > - */
> > - ld r10,PPC64_CACHES@toc(r2)
> > - lwz r7,DCACHEL1BLOCKSIZE(r10)/* Get cache block size */
> > - addi r5,r7,-1
> > - andc r6,r3,r5 /* round low to line bdy */
> > - subf r8,r6,r4 /* compute length */
> > - add r8,r8,r5 /* ensure we get enough */
> > - lwz r9,DCACHEL1LOGBLOCKSIZE(r10) /* Get log-2 of cache block
> > size */
> > - srd. r8,r8,r9 /* compute line count */
> > - beqlr /* nothing to do? */
> > - mtctr r8
> > -1: dcbst 0,r6
> > - add r6,r6,r7
> > - bdnz 1b
> > - sync
> > -
> > -/* Now invalidate the instruction cache */
> > -
> > - lwz r7,ICACHEL1BLOCKSIZE(r10) /* Get Icache block size */
> > - addi r5,r7,-1
> > - andc r6,r3,r5 /* round low to line bdy */
> > - subf r8,r6,r4 /* compute length */
> > - add r8,r8,r5
> > - lwz r9,ICACHEL1LOGBLOCKSIZE(r10) /* Get log-2 of Icache
> > block size */
> > - srd. r8,r8,r9 /* compute line count */
> > - beqlr /* nothing to do? */
> > - mtctr r8
> > -2: icbi 0,r6
> > - add r6,r6,r7
> > - bdnz 2b
> > - isync
> > - blr
> > -_ASM_NOKPROBE_SYMBOL(flush_icache_range)
> > -EXPORT_SYMBOL(flush_icache_range)
> > -
> > -/*
> > - * Flush a particular page from the data cache to RAM.
> > - * Note: this is necessary because the instruction cache does
> > *not*
> > - * snoop from the data cache.
> > - *
> > - * void __flush_dcache_icache(void *page)
> > - */
> > -_GLOBAL(__flush_dcache_icache)
> > -/*
> > - * Flush the data cache to memory
> > - *
> > - * Different systems have different cache line sizes
> > - */
> > -
> > -BEGIN_FTR_SECTION
> > - PURGE_PREFETCHED_INS
> > - blr
> > -END_FTR_SECTION_IFSET(CPU_FTR_COHERENT_ICACHE)
> > -
> > -/* Flush the dcache */
> > - ld r7,PPC64_CACHES@toc(r2)
> > - clrrdi r3,r3,PAGE_SHIFT /* Page align
> > */
> > - lwz r4,DCACHEL1BLOCKSPERPAGE(r7) /* Get # dcache blocks per
> > page */
> > - lwz r5,DCACHEL1BLOCKSIZE(r7) /* Get dcache block size */
> > - mr r6,r3
> > - mtctr r4
> > -0: dcbst 0,r6
> > - add r6,r6,r5
> > - bdnz 0b
> > - sync
> > -
> > -/* Now invalidate the icache */
> > -
> > - lwz r4,ICACHEL1BLOCKSPERPAGE(r7) /* Get # icache blocks per
> > page */
> > - lwz r5,ICACHEL1BLOCKSIZE(r7) /* Get icache block size */
> > - mtctr r4
> > -1: icbi 0,r3
> > - add r3,r3,r5
> > - bdnz 1b
> > - isync
> > - blr
> > -
> > _GLOBAL(__bswapdi2)
> > EXPORT_SYMBOL(__bswapdi2)
> > srdi r8,r3,32
> > diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
> > index 9191a66b3bc5..cd540123874d 100644
> > --- a/arch/powerpc/mm/mem.c
> > +++ b/arch/powerpc/mm/mem.c
> > @@ -321,6 +321,105 @@ void free_initmem(void)
> > free_initmem_default(POISON_FREE_INITMEM);
> > }
> >
> > +/*
> > + * Warning: This macro will perform an early return if the CPU has
> > + * a coherent icache. The intent is is call this early in
> > function,
> > + * and handle the non-coherent icache variant afterwards.
> > + *
> > + * For a snooping icache, we still need a dummy icbi to purge all
> > the
> > + * prefetched instructions from the ifetch buffers. We also need a
> > sync
> > + * before the icbi to order the the actual stores to memory that
> > might
> > + * have modified instructions with the icbi.
> > + */
> > +#define flush_coherent_icache_or_return(addr) {
> > \
> > + if (cpu_has_feature(CPU_FTR_COHERENT_ICACHE)) { \
> > + mb(); /* sync */ \
> > + icbi(addr); \
> > + mb(); /* sync */ \
> > + isync(); \
> > + return; \
> > + } \
> > +}
>
> I hate this kind of awful macro which kills code readability.
>
> Please to something like
>
> static bool flush_coherent_icache_or_return(unsigned long addr)
> {
> if (!cpu_has_feature(CPU_FTR_COHERENT_ICACHE))
> return false;
>
> mb(); /* sync */
> icbi(addr);
> mb(); /* sync */
> isync();
> return true;
> }
>
> then callers will do:
>
> if (flush_coherent_icache_or_return(addr))
> return;

Sounds good.

> > +
> > +/**
> > + * flush_icache_range: Write any modified data cache blocks out to
> > memory
> > + * and invalidate the corresponding blocks in the instruction
> > cache
> > + *
> > + * Generic code will call this after writing memory, before
> > executing from it.
> > + *
> > + * @start: the start address
> > + * @stop: the stop address (exclusive)
> > + */
> > +void flush_icache_range(unsigned long start, unsigned long stop)
> > +{
> > + unsigned long shift = l1_icache_shift();
> > + unsigned long bytes = l1_icache_bytes();
> > + char *addr = (char *)(start & ~(bytes - 1));
> > + unsigned long size = stop - (unsigned long)addr + (bytes - 1);
> > + unsigned long i;
>
> Could probably move all this and the loop into a
> __flush_icache_range()
> helper.

Will factor it out into invalidate_icache_range (as its similar to
invalidate_dcache_range).

>
> > +
> > + flush_coherent_icache_or_return(addr);
> > + clean_dcache_range(start, stop);
> > +
> > + if (IS_ENABLED(CONFIG_44x)) {
> > + /*
> > + * Flash invalidate on 44x because we are passed
> > kmapped
> > + * addresses and this doesn't work for userspace pages
> > due to
> > + * the virtually tagged icache.
> > + */
> > + iccci(addr);
> > + } else {
> > + /* Now invalidate the instruction cache */
> > + for (i = 0; i < size >> shift; i++, addr += bytes)
> > + icbi(addr);
> > + }
> > +
> > + if (!IS_ENABLED(CONFIG_PPC64))
> > + mb(); /* additional sync needed on g4 */
> > + isync();
> > +}
> > +EXPORT_SYMBOL(flush_icache_range);
> > +
> > +#if !defined(CONFIG_PPC_8xx) & !defined(CONFIG_PPC64)
> > +/**
> > + * flush_dcache_icache_phys() - Flush a page by it's physical
> > address
> > + * @physaddr: the physical address of the page
> > + */
> > +static void flush_dcache_icache_phys(unsigned long physaddr)
> > +{
> > + unsigned long bytes = l1_dcache_bytes();
> > + unsigned long nb = PAGE_SIZE / bytes;
> > + unsigned long addr = physaddr & PAGE_MASK;
> > + unsigned long msr, msr0;
> > + unsigned long loop1 = addr, loop2 = addr;
> > +
> > + msr0 = mfmsr();
> > + msr = msr0 & ~MSR_DR;
>
> Maybe we could get rid of msr and just use (msr0 & ~MSR_DR) in the
> asm
> inputs parameters.
>

That's already pretty busy, I think it's clearer as-is.

> > + /*
> > + * This must remain as ASM to prevent potential memory accesses
> > + * while the data MMU is disabled
> > + */
> > + asm volatile(
> > + " mtctr %2;"
> > + " mtmsr %3;"
> > + " isync;"
> > + "0: dcbst 0, %0;"
> > + " addi %0, %0, %4;"
> > + " bdnz 0b;"
> > + " sync;"
> > + " mtctr %2;"
> > + "1: icbi 0, %1;"
> > + " addi %1, %1, %4;"
> > + " bdnz 1b;"
> > + " sync;"
> > + " mtmsr %5;"
> > + " isync;"
> > + : "+r" (loop1), "+r" (loop2)
> > + : "r" (nb), "r" (msr), "i" (bytes), "r" (msr0)
> > + : "ctr", "memory");
>
> Maybe also add "msr" in the clobbers.
>
Ok.

> > +}
> > +#endif // !defined(CONFIG_PPC_8xx) & !defined(CONFIG_PPC64)
> > +
> > /*
> > * This is called when a page has been modified by the kernel.
> > * It just marks the page as not i-cache clean. We do the i-
> > cache
> > @@ -353,12 +452,63 @@ void flush_dcache_icache_page(struct page
> > *page)
> > __flush_dcache_icache(start);
> > kunmap_atomic(start);
> > } else {
> > - __flush_dcache_icache_phys(page_to_pfn(page) <<
> > PAGE_SHIFT);
> > + unsigned long addr = page_to_pfn(page) << PAGE_SHIFT;
> > +
> > + flush_coherent_icache_or_return((void *)addr);
> > + flush_dcache_icache_phys(addr);
> > }
> > #endif
> > }
> > EXPORT_SYMBOL(flush_dcache_icache_page);
> >
> > +/**
> > + * __flush_dcache_icache(): Flush a particular page from the data
> > cache to RAM.
> > + * Note: this is necessary because the instruction cache does
> > *not*
> > + * snoop from the data cache.
> > + *
> > + * @page: the address of the page to flush
> > + */
> > +void __flush_dcache_icache(void *page)
> > +{
> > + char *addr = page;
> > + unsigned long lines = PAGE_SIZE >> l1_dcache_shift();
> > + unsigned long bytes = l1_dcache_bytes();
> > + unsigned long i;
> > +
> > + flush_coherent_icache_or_return(addr);
> > +
> > + /* Flush the data cache to memory */
> > + for (i = 0; i < lines; i++, addr += bytes)
> > + dcbst(addr);
>
> Use clean_dcache_range(addr, addr + PAGE_SIZE);
>
Ok.

> > +
> > + mb(); /* sync */
> > +
> > +#ifdef CONFIG_44x
>
> This ifdef is useless.
> If CONFIG_44x is not enabled, MMU_FTR_TYPE_44x will not be in
> MMU_FTRS_POSSIBLE so cpu_has_feature() will return constant false at
> buildtime and GCC will drop it.
>

Ok.

> > + /*
> > + * We don't flush the icache on 44x. Those have a virtual
> > icache and we
> > + * don't have access to the virtual address here (it's not the
> > page
> > + * vaddr but where it's mapped in user space). The flushing of
> > the
> > + * icache on these is handled elsewhere, when a change in the
> > address
> > + * space occurs, before returning to user space.
> > + */
> > +
> > + if (cpu_has_feature(MMU_FTR_TYPE_44x))
> > + return;
> > +#endif
> > +
> > + lines = PAGE_SIZE >> l1_icache_shift();
> > + bytes = l1_icache_bytes();
> > + addr = page;
> > +
> > + /* Now invalidate the instruction cache */
> > + for (i = 0; i < lines; i++, addr += bytes)
> > + icbi(addr);
>
> Re-use the __flush_icache_range() helper suggested before.
>
Ok.

> > +
> > + mb(); /* sync */
> > + isync();
> > +}
> > +EXPORT_SYMBOL(__flush_dcache_icache);
> > +
> > void clear_user_page(void *page, unsigned long vaddr, struct page
> > *pg)
> > {
> > clear_page(page);
> >
>
> Christophe
--
Alastair D'Silva
Open Source Developer
Linux Technology Centre, IBM Australia
mob: 0423 762 819

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