From: Jan Kiszka <jan.kiszka@web.de>
To: Avi Kivity <avi@redhat.com>
Cc: qemu-devel@nongnu.org, Craig Brozefsky <craig@red-bean.com>
Subject: Re: [Qemu-devel] Re: software breakpoints disappearing/reappearing in KVM/qemu
Date: Sun, 10 Apr 2011 16:23:32 +0200 [thread overview]
Message-ID: <4DA1BD64.6000108@web.de> (raw)
In-Reply-To: <4DA1B81C.8000506@redhat.com>
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On 2011-04-10 16:01, Avi Kivity wrote:
> On 04/08/2011 11:52 PM, Jan Kiszka wrote:
>> QEMU's gdbstub in KVM mode is simply not designed to account for guests
>> swapping out code pages that contain breakpoints. Due to the fact that
>> the Linux kernel does not do these weird things to its own code,
>
> It actually happily patches its own code at certain circumstances. If
> you debug early boot or suspend/resume or cpu hotplug you're likely to
> encounter them.
Yes, it patches (alternates, jump_labels, mcount etc.), but it doesn't
swap or move code pages. At least so far.
If you need to break at such locations, there are still hardware
breakpoints, though only 4.
Jan
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next prev parent reply other threads:[~2011-04-10 14:23 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-08 18:50 [Qemu-devel] software breakpoints disappearing/reappearing in KVM/qemu Craig Brozefsky
2011-04-08 20:16 ` Blue Swirl
2011-04-08 20:37 ` Craig Brozefsky
2011-04-08 20:52 ` [Qemu-devel] " Jan Kiszka
2011-04-10 14:01 ` Avi Kivity
2011-04-10 14:23 ` Jan Kiszka [this message]
2011-04-10 14:41 ` Avi Kivity
2011-04-10 15:16 ` Jan Kiszka
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