Re: [PATCH v2 2/3] powerpc/memcpy: Add memcpy_mcsafe for pmem

[Balbir Singh]

On Thu, Apr 5, 2018 at 9:26 PM, Oliver  wrote:
> On Thu, Apr 5, 2018 at 5:14 PM, Balbir Singh  wrote:
>> The pmem infrastructure uses memcpy_mcsafe in the pmem
>> layer so as to convert machine check excpetions into
>> a return value on failure in case a machine check
>> exception is encoutered during the memcpy.
>>
>
> Would it be possible to move the bulk of the copyuser code into a
> seperate file which can be #included once the these err macros are
> defined? Anton's memcpy is pretty hairy and I don't think anyone wants
> to have multiple copies of it in the tree, even in a cut down form.
>

I've split it out for now, in the future that might be a good thing to do.
The copy_tofrom_user_power7 falls backs on __copy_tofrom_user_base
to track exactly how much is left over. Adding these changes there would
create a larger churn and need way more testing. I've taken this short-cut
for now with a promise to fix that as the semantics of memcpy_mcsafe()
change to do more accurate tracking of how much was copied over.

Balbir Singh.

Re: [PATCH v2 2/3] powerpc/memcpy: Add memcpy_mcsafe for pmem

[Oliver]

On Thu, Apr 5, 2018 at 5:14 PM, Balbir Singh  wrote:
> The pmem infrastructure uses memcpy_mcsafe in the pmem
> layer so as to convert machine check excpetions into
> a return value on failure in case a machine check
> exception is encoutered during the memcpy.
>
> This patch largely borrows from the copyuser_power7
> logic and does not add the VMX optimizations, largely
> to keep the patch simple. If needed those optimizations
> can be folded in.
>
> Signed-off-by: Balbir Singh 
> Acked-by: Nicholas Piggin 
> ---
>  arch/powerpc/include/asm/string.h   |   2 +
>  arch/powerpc/lib/Makefile   |   2 +-
>  arch/powerpc/lib/memcpy_mcsafe_64.S | 212 
> 
>  3 files changed, 215 insertions(+), 1 deletion(-)
>  create mode 100644 arch/powerpc/lib/memcpy_mcsafe_64.S
>
> diff --git a/arch/powerpc/include/asm/string.h 
> b/arch/powerpc/include/asm/string.h
> index 9b8cedf618f4..b7e872a64726 100644
> --- a/arch/powerpc/include/asm/string.h
> +++ b/arch/powerpc/include/asm/string.h
> @@ -30,7 +30,9 @@ extern void * memcpy_flushcache(void *,const void 
> *,__kernel_size_t);
>  #ifdef CONFIG_PPC64
>  #define __HAVE_ARCH_MEMSET32
>  #define __HAVE_ARCH_MEMSET64
> +#define __HAVE_ARCH_MEMCPY_MCSAFE
>
> +extern int memcpy_mcsafe(void *dst, const void *src, __kernel_size_t sz);
>  extern void *__memset16(uint16_t *, uint16_t v, __kernel_size_t);
>  extern void *__memset32(uint32_t *, uint32_t v, __kernel_size_t);
>  extern void *__memset64(uint64_t *, uint64_t v, __kernel_size_t);
> diff --git a/arch/powerpc/lib/Makefile b/arch/powerpc/lib/Makefile
> index 3c29c9009bbf..048afee9f518 100644
> --- a/arch/powerpc/lib/Makefile
> +++ b/arch/powerpc/lib/Makefile
> @@ -24,7 +24,7 @@ endif
>
>  obj64-y+= copypage_64.o copyuser_64.o mem_64.o hweight_64.o \
>copyuser_power7.o string_64.o copypage_power7.o memcpy_power7.o \
> -  memcpy_64.o memcmp_64.o pmem.o
> +  memcpy_64.o memcmp_64.o pmem.o memcpy_mcsafe_64.o
>
>  obj64-$(CONFIG_SMP)+= locks.o
>  obj64-$(CONFIG_ALTIVEC)+= vmx-helper.o
> diff --git a/arch/powerpc/lib/memcpy_mcsafe_64.S 
> b/arch/powerpc/lib/memcpy_mcsafe_64.S
> new file mode 100644
> index ..e7eaa9b6cded
> --- /dev/null
> +++ b/arch/powerpc/lib/memcpy_mcsafe_64.S
> @@ -0,0 +1,212 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (C) IBM Corporation, 2011
> + * Derived from copyuser_power7.s by Anton Blanchard 
> + * Author - Balbir Singh 
> + */
> +#include 
> +#include 
> +
> +   .macro err1
> +100:
> +   EX_TABLE(100b,.Ldo_err1)
> +   .endm
> +
> +   .macro err2
> +200:
> +   EX_TABLE(200b,.Ldo_err2)
> +   .endm

Would it be possible to move the bulk of the copyuser code into a
seperate file which can be #included once the these err macros are
defined? Anton's memcpy is pretty hairy and I don't think anyone wants
to have multiple copies of it in the tree, even in a cut down form.

> +
> +.Ldo_err2:
> +   ld  r22,STK_REG(R22)(r1)
> +   ld  r21,STK_REG(R21)(r1)
> +   ld  r20,STK_REG(R20)(r1)
> +   ld  r19,STK_REG(R19)(r1)
> +   ld  r18,STK_REG(R18)(r1)
> +   ld  r17,STK_REG(R17)(r1)
> +   ld  r16,STK_REG(R16)(r1)
> +   ld  r15,STK_REG(R15)(r1)
> +   ld  r14,STK_REG(R14)(r1)
> +   addir1,r1,STACKFRAMESIZE
> +.Ldo_err1:
> +   li  r3,-EFAULT
> +   blr
> +
> +
> +_GLOBAL(memcpy_mcsafe)
> +   cmpldi  r5,16
> +   blt .Lshort_copy
> +
> +.Lcopy:
> +   /* Get the source 8B aligned */
> +   neg r6,r4
> +   mtocrf  0x01,r6
> +   clrldi  r6,r6,(64-3)
> +
> +   bf  cr7*4+3,1f
> +err1;  lbz r0,0(r4)
> +   addir4,r4,1
> +err1;  stb r0,0(r3)
> +   addir3,r3,1
> +
> +1: bf  cr7*4+2,2f
> +err1;  lhz r0,0(r4)
> +   addir4,r4,2
> +err1;  sth r0,0(r3)
> +   addir3,r3,2
> +
> +2: bf  cr7*4+1,3f
> +err1;  lwz r0,0(r4)
> +   addir4,r4,4
> +err1;  stw r0,0(r3)
> +   addir3,r3,4
> +
> +3: sub r5,r5,r6
> +   cmpldi  r5,128
> +   blt 5f
> +
> +   mflrr0
> +   stdur1,-STACKFRAMESIZE(r1)
> +   std r14,STK_REG(R14)(r1)
> +   std r15,STK_REG(R15)(r1)
> +   std r16,STK_REG(R16)(r1)
> +   std r17,STK_REG(R17)(r1)
> +   std r18,STK_REG(R18)(r1)
> +   std r19,STK_REG(R19)(r1)
> +   std r20,STK_REG(R20)(r1)
> +   std r21,STK_REG(R21)(r1)
> +   std r22,STK_REG(R22)(r1)
> +   std r0,STACKFRAMESIZE+16(r1)
> +
> +   srdir6,r5,7
> +   mtctr   r6
> +
> +   /* Now do cacheline (128B) sized loads and stores. */
> +   .align  5
> +4:
> +err2;  ld  r0,0(r4)
> +err2;  ld  r6,8(r4)
> +err2;  ld  r7,16(r4)
> +err2;  ld  r8,24(r4)
> +err2;  ld