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Re: [Qemu-devel] [RFC 20/38] tcg/i386: implement fences
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [RFC 20/38] tcg/i386: implement fences |
Date: |
Tue, 25 Aug 2015 18:55:53 -0400 (EDT) |
> lfence and sfence here serve two purposes:
>
> 1) Template for other architectures
Ok, this makes sense.
> 2) x86 code does sometimes have lfence/sfence (e.g. movntq+sfence),
> so I guessed they should remain in the translated code.
> If on x86 we always ignore the Write-Combining from the
> guest, maybe we could claim the l/sfence pair here is really unnecessary.
Yeah, I think it's fair enough to ignore WC and nontemporal stores.
> I didn't intend to translate say *all* PPC/ARM load barriers
> into lfences when generating x86, which is I think your point.
Yeah, it's just that the only gen_op_smp_rmb() you had in the RFC
also did not need an lfence. But it seems like we're on the same
page.
Paolo
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- [Qemu-devel] [RFC 15/38] radix-tree: add generic lockless radix tree module, Emilio G. Cota, 2015/08/23
- [Qemu-devel] [RFC 16/38] aie: add module for Atomic Instruction Emulation, Emilio G. Cota, 2015/08/23
- [Qemu-devel] [RFC 20/38] tcg/i386: implement fences, Emilio G. Cota, 2015/08/23
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