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Re: [Qemu-ppc] [Qemu-devel] [PATCH v3] tcg/ppc: Improve unaligned load/s
From: |
Richard Henderson |
Subject: |
Re: [Qemu-ppc] [Qemu-devel] [PATCH v3] tcg/ppc: Improve unaligned load/store handling on 64-bit backend |
Date: |
Fri, 24 Jul 2015 05:34:39 -0700 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 |
On 07/20/2015 10:19 PM, Benjamin Herrenschmidt wrote:
> Currently, we get to the slow path for any unaligned access in the
> backend, because we effectively preserve the bottom address bits
> below the alignment requirement when comparing with the TLB entry,
> so any non-0 bit there will cause the compare to fail.
>
> For the same number of instructions, we can instead add the access
> size - 1 to the address and stick to clearing all the bottom bits.
>
> That means that normal unaligned accesses will not fallback (the HW
> will handle them fine). Only when crossing a page boundary well we
> end up having a mismatch because we'll end up pointing to the next
> page which cannot possibly be in that same TLB entry.
>
> Signed-off-by: Benjamin Herrenschmidt <address@hidden>
> ---
>
> v3. Add MO_ALIGN support for front-ends requiring aligned accesses
> v2. This is the correct version of the patch, the one that
> actually works :-)
>
> tcg/ppc/tcg-target.c | 41 +++++++++++++++++++++++++++++++----------
> 1 file changed, 31 insertions(+), 10 deletions(-)
Applied to tcg-next.
r~
- Re: [Qemu-ppc] [PATCH v3] tcg/ppc: Improve unaligned load/store handling on 64-bit backend, (continued)
- Re: [Qemu-ppc] [PATCH v3] tcg/ppc: Improve unaligned load/store handling on 64-bit backend, Richard Henderson, 2015/07/21
- Re: [Qemu-ppc] [PATCH v3] tcg/ppc: Improve unaligned load/store handling on 64-bit backend, Benjamin Herrenschmidt, 2015/07/21
- Re: [Qemu-ppc] [PATCH v3] tcg/ppc: Improve unaligned load/store handling on 64-bit backend, Alexander Graf, 2015/07/21
- Re: [Qemu-ppc] [PATCH v3] tcg/ppc: Improve unaligned load/store handling on 64-bit backend, Benjamin Herrenschmidt, 2015/07/21
- Re: [Qemu-ppc] [PATCH v3] tcg/ppc: Improve unaligned load/store handling on 64-bit backend, Paolo Bonzini, 2015/07/21
- Re: [Qemu-ppc] [PATCH v3] tcg/ppc: Improve unaligned load/store handling on 64-bit backend, Alexander Graf, 2015/07/21
- Re: [Qemu-ppc] [PATCH v3] tcg/ppc: Improve unaligned load/store handling on 64-bit backend, Benjamin Herrenschmidt, 2015/07/21
- Re: [Qemu-ppc] [PATCH v3] tcg/ppc: Improve unaligned load/store handling on 64-bit backend, Benjamin Herrenschmidt, 2015/07/21
- Re: [Qemu-ppc] [PATCH v3] tcg/ppc: Improve unaligned load/store handling on 64-bit backend, Aurelien Jarno, 2015/07/21
Re: [Qemu-ppc] [PATCH v3] tcg/ppc: Improve unaligned load/store handling on 64-bit backend, Aurelien Jarno, 2015/07/21
Re: [Qemu-ppc] [Qemu-devel] [PATCH v3] tcg/ppc: Improve unaligned load/store handling on 64-bit backend,
Richard Henderson <=