On 03/07/2013 02:06:05 AM, Jia Hongtao-B38951 wrote:
Here is the ideas from Scott:
"
> + if (is_in_pci_mem_space(addr)) {
> + inst = *(unsigned int *)regs->nip;
Be careful about taking a fault here. A simple TLB miss should be
safe
given that we shouldn't be accessing PCIe in the middle of exception
code, but what if the mapping has gone away (e.g. a userspace driver
had
its code munmap()ed or swapped out)? What if permissions allow
execute
but not read (not sure if Linux will allow this, but the hardware
does)?
What if it happened in a KVM guest? You can't access guest addresses
directly.
"
That means you need to be careful about how you read the instruction,
not that you shouldn't do it at all.
-Scott
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