From: "Emilio G. Cota" <cota@braap.org>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH] translate-all: use bitmap helpers for PageDesc's bitmap
Date: Wed, 22 Apr 2015 12:47:01 -0400 [thread overview]
Message-ID: <20150422164701.GA2378@flamenco> (raw)
In-Reply-To: <55379E61.5080104@redhat.com>
On Wed, Apr 22, 2015 at 15:13:05 +0200, Paolo Bonzini wrote:
> On 21/03/2015 07:25, Emilio G. Cota wrote:
> > Note that this test
> > if (b & ((1 << len) - 1))
> > can be simplified to
> > if (b & 1)
> > , since we know that iff the first bit of a tb is set,
> > all other bits from that tb are set too.
>
> I don't think this optimization is valid, unfortunately. It is possible
> that say a tb starts at 0x12340001 and tb_invalidate_phys_page_fast is
> called for the range starting at 0x12340000 and ending at 0x12340003.
>
> In this case you need the full test that was used before.
Good catch, haven't seen this in my tests but it could possibly happen.
v2 coming up.
Thanks,
Emilio
next prev parent reply other threads:[~2015-04-22 16:46 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-21 6:25 [Qemu-devel] [PATCH] translate-all: use bitmap helpers for PageDesc's bitmap Emilio G. Cota
2015-04-03 0:08 ` Emilio G. Cota
2015-04-03 14:18 ` Paolo Bonzini
2015-04-22 13:13 ` Paolo Bonzini
2015-04-22 16:47 ` Emilio G. Cota [this message]
2015-04-22 16:53 ` [Qemu-devel] [PATCH v2] " Emilio G. Cota
2015-04-22 20:30 ` Paolo Bonzini
2015-04-22 21:47 ` Emilio G. Cota
2015-04-22 21:50 ` [Qemu-devel] [PATCH v3] " Emilio G. Cota
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