On Tue, 25 Sep 2012 18:15:50 +0100, Peter Maydell
<[email protected]> wrote:
> On 25 September 2012 18:00, Will Deacon <[email protected]> wrote:
>> On Sat, Sep 15, 2012 at 04:35:33PM +0100, Christoffer Dall wrote:
>>> ENTRY(__kvm_tlb_flush_vmid)
>>> + hvc #0 @ Switch to Hyp mode
>>> + push {r2, r3}
>>> +
>>> + add r0, r0, #KVM_VTTBR
>>> + ldrd r2, r3, [r0]
>>> + mcrr p15, 6, r2, r3, c2 @ Write VTTBR
>>> + isb
>>> + mcr p15, 0, r0, c8, c3, 0 @ TLBIALLIS (rt ignored)
>>> + dsb
>>> + isb
>>> + mov r2, #0
>>> + mov r3, #0
>>> + mcrr p15, 6, r2, r3, c2 @ Back to VMID #0
>>> + isb
>>
>> Do you need this isb, given that you're about to do an hvc?
>>
>>> + pop {r2, r3}
>>> + hvc #0 @ Back to SVC
>>> bx lr
>
> ...you probably don't want to do the memory accesses involved
> in the 'pop' under the wrong VMID ?
Well, we're still in HYP mode when performing the pop, so the VMID is
pretty much irrelevant. Same for the initial push, actually. As long as
we're sure VTTBR has been updated when we do the exception return, I think
we're safe.
M.
--
Fast, cheap, reliable. Pick two.
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