On 03/07/2016 11:09 AM, Rob Gardner wrote:

On 03/07/2016 10:04 AM, Khalid Aziz wrote:

quoted

On 03/07/2016 09:56 AM, David Miller wrote:

quoted

From: Khalid Aziz <redacted>
Date: Mon, 7 Mar 2016 08:07:53 -0700

quoted

PR_GET_SPARC_ADICAPS

Put this into a new ELF auxiliary vector entry via ARCH_DLINFO.

So now all that's left is supposedly the TAG stuff, please explain
that to me so I can direct you to the correct existing interface to
provide that as well.

Really, try to avoid prtctl, it's poorly typed and almost worse than
ioctl().

The two remaining operations I am looking at are:

1. Is PSTATE.mcde bit set for the process? PR_SET_SPARC_ADI provides
this in its return value in the patch I sent.

2. Is TTE.mcd set for a given virtual address? PR_GET_SPARC_ADI_STATUS
provides this function in the patch I sent.

Setting and clearing version tags can be done entirely from userspace:

        while (addr < end) {
                asm volatile(
                        "stxa %1, [%0]ASI_MCD_PRIMARY\n\t"
                        :
                        : "r" (addr), "r" (version));
                addr += adicap.blksz;
        }
so I do not have to add any kernel code for tags.

What about clearing the tags when the user is done with the memory? You
can't count on the user to do that, so doesn't the kernel have to do it
someplace?

Tags can be cleared by user by setting tag to 0. Tags are automatically 
cleared by the hardware when the mapping for a virtual address is 
removed from TSB (which is why swappable pages are a problem), so kernel 
does not have to do it as part of clean up.

Thanks,
Khalid

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>