Re: [lhcs-devel] Re: in_atomic doesn't count local_irq_disable?

[Srivatsa Vaddagiri <vatsa@in.ibm.com>]

On Fri, Jan 02, 2004 at 01:52:07AM +0100, Manfred Spraul wrote:
> Could you write a test module that reads cr2, executes a few prefetch 
> instructions and then checks if cr2 changed? I won't have access to my 
> P3 SMP system in the next few days.
 
Hi Manfred,
	I wrote a test module and found that CR2 remains same across the 
prefetch. The module source I used is as below. Note that I had
to used "my_prefetch" because the original prefetch (in asm/processor.h) 
has been disabled in my tree to do nothing.



inline void my_prefetch(const void *x)
{
        alternative_input(ASM_NOP4,
                          "prefetchnta (%1)",
                          X86_FEATURE_XMM,
                          "r" (x));
}

int array[10];

static int __init dummy_init_module(void)
{
        unsigned long address;
        int i=0;
        int x;

        /* get the address */
        __asm__("movl %%cr2,%0":"=r" (address));

        printk ("CR2 before prefetch is %x \n", address);

        for (i=0; i<10; ++i)
                my_prefetch(array+i);

        for (i=0; i<10; ++i)
                x = *(array+i);

        /* get the address */
        __asm__("movl %%cr2,%0":"=r" (address));


        printk ("CR2 after prefetch is %x \n", address);


        return 0;

}


static void __exit dummy_cleanup_module(void)
{
}

module_init(dummy_init_module);
module_exit(dummy_cleanup_module);
MODULE_LICENSE("GPL");


Output of the above printk is :


CR2 before prefetch is 40017000
CR2 after prefetch is 40017000








-- 


Thanks and Regards,
Srivatsa Vaddagiri,
Linux Technology Center,
IBM Software Labs,
Bangalore, INDIA - 560017