[PATCH v2 4/4] KVM: PPC: Bookehv: Get vcpu's last instruction for emulation
agraf at suse.de
Fri May 2 21:10:51 EST 2014
On 05/02/2014 12:12 PM, David Laight wrote:
> From: Alexander Graf
>>> + page = pfn_to_page(pfn);
>>> + eaddr = (unsigned long)kmap_atomic(page);
>>> + eaddr |= addr & ~PAGE_MASK;
>>> + *instr = *(u32 *)eaddr;
>>> + kunmap_atomic((u32 *)eaddr);
>> I think I'd rather write this as
>> *instr = *(u32 *)(eaddr | (addr & ~PAGE));
>> to make sure we pass the unmap function the same value we got from the
>> map function.
>> Otherwise looks good to me.
> Is there any mileage in keeping a virtual address page allocated (per cpu)
> for this (and similar) accesses to physical memory?
> Not having to search for a free VA page might speed things up (if that matters).
I like the idea, though I'm not sure how that would best fit into the
current memory mapping ecosystem.
> You also probably want the page mapped uncached - no point polluting the data
Do e500 chips have a shared I/D cache somewhere? If they do, that
particular instruction would already be there, so no pollution but nice
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