From: Avi Kivity <avi@redhat.com>
To: Gleb Natapov <gleb@redhat.com>
Cc: kvm@vger.kernel.org, mtosatti@redhat.com
Subject: Re: [PATCHv4 4/5] KVM: emulator: make linearize() callable from outside of emulator
Date: Thu, 19 Jul 2012 15:52:15 +0300 [thread overview]
Message-ID: <500802FF.3030909@redhat.com> (raw)
In-Reply-To: <20120719105158.GV26120@redhat.com>
On 07/19/2012 01:51 PM, Gleb Natapov wrote:
>> > +int x86_linearize(struct x86_linearize_params *p, ulong *linear)
>> > {
>> > - struct desc_struct desc;
>> > - bool usable;
>> > ulong la;
>> > u32 lim;
>> > - u16 sel;
>> > unsigned cpl, rpl;
>> >
>> > - la = seg_base(ctxt, addr.seg) + addr.ea;
>> > - switch (ctxt->mode) {
>> > + la = get_desc_base(&p->desc) + p->ea;
>>
>> This makes 64-bit mode slower, since before the patch it avoided reading
>> the segment base for non-fs/gs segments, and only read the segment base
>> for fs/gs. After the patch we always execute 4 VMREADs (and decode the
>> results).
>>
> That's easy to fix by making caller prepare fake desc if mode is 64-bit
> and segment is non-fs/gs. The question is if this even measurable?
I'm sure it will be measurable, esp. on older processors. Why not
measure it?
--
error compiling committee.c: too many arguments to function
next prev parent reply other threads:[~2012-07-19 12:52 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-19 7:40 [PATCHv4 0/5] improve speed of "rep ins" emulation Gleb Natapov
2012-07-19 7:40 ` [PATCHv4 1/5] Provide userspace IO exit completion callback Gleb Natapov
2012-07-19 7:40 ` [PATCHv4 2/5] KVM: emulator: make x86 emulation modes enum instead of defines Gleb Natapov
2012-07-19 7:40 ` [PATCHv4 3/5] KVM: emulator: move some address manipulation function out of emulator code Gleb Natapov
2012-07-19 10:42 ` Avi Kivity
2012-07-19 10:49 ` Gleb Natapov
2012-07-19 13:34 ` Avi Kivity
2012-07-19 13:43 ` Gleb Natapov
2012-07-19 7:40 ` [PATCHv4 4/5] KVM: emulator: make linearize() callable from outside of emulator Gleb Natapov
2012-07-19 10:32 ` Avi Kivity
2012-07-19 10:51 ` Gleb Natapov
2012-07-19 12:52 ` Avi Kivity [this message]
2012-07-19 12:54 ` Gleb Natapov
2012-07-19 7:40 ` [PATCHv4 5/5] KVM: Provide fast path for "rep ins" emulation if possible Gleb Natapov
2012-07-19 10:37 ` Avi Kivity
2012-07-19 11:09 ` Gleb Natapov
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