Re: [kvm-unit-test PATCH v2] powerpc: Add emulator test for the lswi instruction

[Laurent Vivier <lvivier@redhat.com>]

On 14/04/2016 16:49, Thomas Huth wrote:
> This test checks some special cases of the lswi instruction. Test
> works fine on real hardware, but in QEMU, this reveals a bug with
> the final "don't overwrite Ra" test (RA gets destroyed since the
> check in QEMU is still wrong).
> The code is based on the lswx test by Laurent Vivier.
> 
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>  v2: Do not clobber r2 during the final test, since it is needed by
>      the exception handler
> 
>  powerpc/emulator.c | 124 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 124 insertions(+)
> 
> diff --git a/powerpc/emulator.c b/powerpc/emulator.c
> index 3696d83..4dc341f 100644
> --- a/powerpc/emulator.c
> +++ b/powerpc/emulator.c
> @@ -71,6 +71,129 @@ static void test_64bit(void)
>  	report_prefix_pop();
>  }
>  
> +/**
> + * Test 'Load String Word Immediate' instruction
> + */
> +static void test_lswi(void)
> +{
> +	int i;
> +	char addr[128];
> +	uint64_t regs[32];
> +
> +	report_prefix_push("lswi");
> +
> +	/* fill memory with sequence */
> +	for (i = 0; i < 128; i++)
> +		addr[i] = 1 + i;
> +
> +	/* check incomplete register filling */
> +	alignment = 0;
> +	asm volatile ("li r12,-1;"
> +		      "mr r11, r12;"
> +		      "lswi r11, %[addr], %[len];"
> +		      "std r11, 0*8(%[regs]);"
> +		      "std r12, 1*8(%[regs]);"
> +		      ::
> +		      [len] "i" (3),
> +		      [addr] "b" (addr),
> +		      [regs] "r" (regs)
> +		      :
> +		      "r11", "r12", "memory");
> +
> +#if  __BYTE_ORDER__ = __ORDER_LITTLE_ENDIAN__
> +	/*
> +	 * lswi is supposed to cause an alignment exception in little endian
> +	 * mode, but QEMU does not support it. So in case we do not get an
> +	 * exception, this is an expected failure and we run the other tests
> +	 */
> +	report_xfail("alignment", !alignment, alignment);
> +	if (alignment) {
> +		report_prefix_pop();
> +		return;
> +	}
> +#endif
> +	report("partial", regs[0] = 0x01020300 && regs[1] = (uint64_t)-1);
> +
> +	/* check NB = 0 => 32 bytes. */
> +	asm volatile ("li r19,-1;"
> +		      "mr r11, r19; mr r12, r19; mr r13, r19;"
> +		      "mr r14, r19; mr r15, r19; mr r16, r19;"
> +		      "mr r17, r19; mr r18, r19;"
> +		      "lswi r11, %[addr], %[len];"
> +		      "std r11, 0*8(%[regs]);"
> +		      "std r12, 1*8(%[regs]);"
> +		      "std r13, 2*8(%[regs]);"
> +		      "std r14, 3*8(%[regs]);"
> +		      "std r15, 4*8(%[regs]);"
> +		      "std r16, 5*8(%[regs]);"
> +		      "std r17, 6*8(%[regs]);"
> +		      "std r18, 7*8(%[regs]);"
> +		      "std r19, 8*8(%[regs]);"
> +		      ::
> +		      [len] "i" (0),
> +		      [addr] "b" (addr),
> +		      [regs] "r" (regs)
> +		      :
> +		      /* as 32 is the number of bytes,
> +		       * we should modify 32/4 = 8 regs, from r11 to r18
> +		       * We check r19 is unmodified by filling it with 1s
> +		       * before the instruction.
> +		       */
> +		      "r11", "r12", "r13", "r14", "r15", "r16", "r17",
> +		      "r18", "r19", "memory");
> +
> +	report("length", regs[0] = 0x01020304 && regs[1] = 0x05060708 &&
> +			 regs[2] = 0x090a0b0c && regs[3] = 0x0d0e0f10 &&
> +			 regs[4] = 0x11121314 && regs[5] = 0x15161718 &&
> +			 regs[6] = 0x191a1b1c && regs[7] = 0x1d1e1f20 &&
> +			 regs[8] = (uint64_t)-1);
> +
> +	/* check wrap around to r0 */
> +	asm volatile ("li r31,-1;"
> +		      "mr r0, r31;"
> +		      "lswi r31, %[addr], %[len];"
> +		      "std r31, 0*8(%[regs]);"
> +		      "std r0, 1*8(%[regs]);"
> +		      ::
> +		      [len] "i" (8),
> +		      [addr] "b" (addr),
> +		      [regs] "r" (regs)
> +		      :
> +		      /* modify two registers from r31, wrap around to r0 */
> +		      "r31", "r0", "memory");
> +
> +	report("wrap around to r0", regs[0] = 0x01020304 &&
> +			            regs[1] = 0x05060708);
> +
> +	/* check wrap around doesn't break RA */
> +	asm volatile ("mr r29,r1\n"
> +		      "li r31,-1\n"
> +		      "mr r0,r31\n"
> +		      "mr r1, %[addr]\n"
> +		      ".long 0x7fe154aa\n"       /* lswi r31, r1, 10 */

Perhaps you can add a comment explaining why you are using a .long
instead of the mnemonic?

Anyway:

Reviewed-by: Laurent Vivier <lvivier@redhat.com>

> +		      "std r31, 0*8(%[regs])\n"
> +		      "std r0, 1*8(%[regs])\n"
> +		      "std r1, 2*8(%[regs])\n"
> +		      "mr r1,r29\n"
> +		      ::
> +		      [addr] "r" (addr),
> +		      [regs] "r" (regs)
> +		      :
> +		      /* loading three registers from r31 wraps around to r1,
> +		       * r1 is saved to r29, as adding it to the clobber
> +		       * list doesn't protect it
> +		       */
> +		      "r0", "r29", "r31", "memory");
> +
> +	/* doc says it is invalid, real proc stops when it comes to
> +	 * overwrite the register.
> +	 * In all the cases, the register must stay untouched
> +	 */
> +	report("Don't overwrite Ra", regs[2] = (uint64_t)addr);
> +
> +	report_prefix_pop();
> +}
> +
>  /*
>   * lswx: Load String Word Indexed X-form
>   *
> @@ -235,6 +358,7 @@ int main(int argc, char **argv)
>  	test_64bit();
>  	test_illegal();
>  	test_lswx();
> +	test_lswi();
>  
>  	report_prefix_pop();
>  
>