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Re: [Qemu-devel] [PATCH v3] tcg/ppc: Improve unaligned load/store handli
From: |
Aurelien Jarno |
Subject: |
Re: [Qemu-devel] [PATCH v3] tcg/ppc: Improve unaligned load/store handling on 64-bit backend |
Date: |
Tue, 21 Jul 2015 17:29:12 +0200 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
On 2015-07-21 15:19, 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>
Reviewed-by: Aurelien Jarno <address@hidden>
--
Aurelien Jarno GPG: 4096R/1DDD8C9B
address@hidden http://www.aurel32.net
- Re: [Qemu-devel] [PATCH v3] tcg/ppc: Improve unaligned load/store handling on 64-bit backend, (continued)
- Re: [Qemu-devel] [PATCH v3] tcg/ppc: Improve unaligned load/store handling on 64-bit backend, Benjamin Herrenschmidt, 2015/07/21
- Re: [Qemu-devel] [PATCH v3] tcg/ppc: Improve unaligned load/store handling on 64-bit backend, Richard Henderson, 2015/07/21
- Re: [Qemu-devel] [PATCH v3] tcg/ppc: Improve unaligned load/store handling on 64-bit backend, Benjamin Herrenschmidt, 2015/07/21
- Re: [Qemu-devel] [PATCH v3] tcg/ppc: Improve unaligned load/store handling on 64-bit backend, Alexander Graf, 2015/07/21
- Re: [Qemu-devel] [PATCH v3] tcg/ppc: Improve unaligned load/store handling on 64-bit backend, Benjamin Herrenschmidt, 2015/07/21
- Re: [Qemu-devel] [PATCH v3] tcg/ppc: Improve unaligned load/store handling on 64-bit backend, Paolo Bonzini, 2015/07/21
- Re: [Qemu-devel] [PATCH v3] tcg/ppc: Improve unaligned load/store handling on 64-bit backend, Alexander Graf, 2015/07/21
- Re: [Qemu-devel] [PATCH v3] tcg/ppc: Improve unaligned load/store handling on 64-bit backend, Benjamin Herrenschmidt, 2015/07/21
- Re: [Qemu-devel] [PATCH v3] tcg/ppc: Improve unaligned load/store handling on 64-bit backend, Benjamin Herrenschmidt, 2015/07/21
- Re: [Qemu-devel] [PATCH v3] tcg/ppc: Improve unaligned load/store handling on 64-bit backend, Aurelien Jarno, 2015/07/21
Re: [Qemu-devel] [PATCH v3] tcg/ppc: Improve unaligned load/store handling on 64-bit backend,
Aurelien Jarno <=
Re: [Qemu-devel] [PATCH v3] tcg/ppc: Improve unaligned load/store handling on 64-bit backend, Richard Henderson, 2015/07/24