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Re: [Qemu-devel] best way to implement emulation of AArch64 tagged addre
From: |
Peter Maydell |
Subject: |
Re: [Qemu-devel] best way to implement emulation of AArch64 tagged addresses |
Date: |
Mon, 4 Apr 2016 17:31:11 +0100 |
On 4 April 2016 at 17:28, Richard Henderson <address@hidden> wrote:
> On 04/04/2016 08:51 AM, Peter Maydell wrote:
>> In particular I think if you just do the relevant handling of the tag
>> bits in target-arm's get_phys_addr() and its subroutines then this
>> should work ok, with the exceptions that:
>> * the QEMU TLB code will think that [tag A + address X] and
>> [tag B + address X] are different virtual addresses and they will
>> miss each other in the TLB
>
>
> Yep. Not only miss, but actively contend with each other.
Yes. Can we avoid that, or do we just have to live with it? I guess
if the TCG fast path is doing a compare on full insn+tag then we
pretty much have to live with it.
>> * tlb invalidate by address becomes nasty because we need to invalidate
>> [every tag + address X]
>
> Hmm. We should require only one flush for X. But the common code doesn't
> know that... I suppose a new tlb_flush_page_mask would do the trick.
Yes, I think we would need that.
>> Can we fix those just by having arm_tlb_fill() call
>> tlb_set_page_with_attrs() with the vaddr with the tag masked out?
>
> No, that misses when we perform the full vaddr+tag comparison on the TCG
> fast path.
Rats, you're right.
thanks
-- PMM
- [Qemu-devel] best way to implement emulation of AArch64 tagged addresses, Peter Maydell, 2016/04/04
- Re: [Qemu-devel] best way to implement emulation of AArch64 tagged addresses, Richard Henderson, 2016/04/04
- Re: [Qemu-devel] best way to implement emulation of AArch64 tagged addresses,
Peter Maydell <=
- Re: [Qemu-devel] best way to implement emulation of AArch64 tagged addresses, Richard Henderson, 2016/04/04
- Re: [Qemu-devel] best way to implement emulation of AArch64 tagged addresses, Tom Hanson, 2016/04/08
- Re: [Qemu-devel] best way to implement emulation of AArch64 tagged addresses, Peter Maydell, 2016/04/08
- Re: [Qemu-devel] best way to implement emulation of AArch64 tagged addresses, Richard Henderson, 2016/04/08
- Re: [Qemu-devel] best way to implement emulation of AArch64 tagged addresses, Thomas Hanson, 2016/04/08
- Re: [Qemu-devel] best way to implement emulation of AArch64 tagged addresses, Richard Henderson, 2016/04/09
- Re: [Qemu-devel] best way to implement emulation of AArch64 tagged addresses, Thomas Hanson, 2016/04/11
- Re: [Qemu-devel] best way to implement emulation of AArch64 tagged addresses, Tom Hanson, 2016/04/13
Re: [Qemu-devel] best way to implement emulation of AArch64 tagged addresses, Peter Maydell, 2016/04/04