From: Rik van Riel <riel@redhat.com>
To: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Gleb Natapov <gleb@redhat.com>, Ingo Molnar <mingo@redhat.com>,
"H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: [RFCv3][PATCH 2/3] fix kvm's use of __pa() on percpu areas
Date: Tue, 15 Jan 2013 13:38:13 -0500 [thread overview]
Message-ID: <50F5A215.5020708@redhat.com> (raw)
In-Reply-To: <20130109185905.0DCFC236@kernel.stglabs.ibm.com>
On 01/09/2013 01:59 PM, Dave Hansen wrote:
> In short, it is illegal to call __pa() on an address holding
> a percpu variable. The times when this actually matters are
> pretty obscure (certain 32-bit NUMA systems), but it _does_
> happen. It is important to keep KVM guests working on these
> systems because the real hardware is getting harder and
> harder to find.
>
> This bug manifested first by me seeing a plain hang at boot
> after this message:
>
> CPU 0 irqstacks, hard=f3018000 soft=f301a000
>
> or, sometimes, it would actually make it out to the console:
>
> [ 0.000000] BUG: unable to handle kernel paging request at ffffffff
>
> I eventually traced it down to the KVM async pagefault code.
> This can be worked around by disabling that code either at
> compile-time, or on the kernel command-line.
Acked-by: Rik van Riel <riel@redhat.com>
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next prev parent reply other threads:[~2013-01-15 18:38 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-09 18:59 [RFCv3][PATCH 1/3] create slow_virt_to_phys() Dave Hansen
2013-01-09 18:59 ` [RFCv3][PATCH 2/3] fix kvm's use of __pa() on percpu areas Dave Hansen
2013-01-15 18:38 ` Rik van Riel [this message]
2013-01-09 18:59 ` [RFCv3][PATCH 3/3] make DEBUG_VIRTUAL work earlier in boot Dave Hansen
2013-01-15 17:04 ` [RFCv3][PATCH 1/3] create slow_virt_to_phys() Rik van Riel
2013-01-15 19:46 ` H. Peter Anvin
2013-01-15 22:50 ` Dave Hansen
2013-01-15 23:46 ` H. Peter Anvin
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