linux-kernel - Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests

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Message-ID: <20170316212635-mutt-send-email-mst@kernel.org>
Date:   Thu, 16 Mar 2017 21:27:56 +0200
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     "Gabriel L. Somlo" <gsomlo@...il.com>
Cc:     Radim Krčmář <rkrcmar@...hat.com>,
        linux-kernel@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests

On Thu, Mar 16, 2017 at 03:24:41PM -0400, Gabriel L. Somlo wrote:
> On Thu, Mar 16, 2017 at 08:29:32PM +0200, Michael S. Tsirkin wrote:
> > Let's take a step back and try to figure out how is
> > mwait called. How about dumping code of VCPUs
> > around mwait?  gdb disa command will do this.
> 
> Started guest with '-s', tried to attach from gdb with
> "target remote localhost:1234", got
> "remote 'g' packet reply is too long: <lengthy string of numbers>"

Try

set arch x86-64:x86-64


> Tried typing 'cont' in the qemu monitor, got os x to crash:
> 
> panic (cpu 1 caller 0xffffff7f813ff488): pmLock: waited too long, held
> by 0xffffff7f813eff65
> 
> Hmm, maybe that's where it keeps its monitor/mwait idle loop.
> Restarted the guest, tried this from monitor:
> 
> 	dump-guest-memory foobar 0xffffff7f813e0000 0x20000
> 
> Got "'dump-guest-memory' has failed: integer is for 32-bit values"
> 
> Hmmm... I have no idea what I'm doing anymore at this point... :)
> 
> --G

I think 0xffffff7f813ff488 is a PC.

-- 
MST