From: Segher Boessenkool <segher@kernel.crashing.org>
To: Paul Mackerras <paulus@samba.org>
Cc: Linuxppc-dev <linuxppc-dev@ozlabs.org>,
KVM list <kvm@vger.kernel.org>,
kvm-ppc@vger.kernel.org, Alexander Graf <agraf@suse.de>
Subject: Re: [PATCH 10/13] kvm/powerpc: Add support for Book3S processors in hypervisor mode
Date: Fri, 27 May 2011 20:59:41 +0000 [thread overview]
Message-ID: <b833d9df4fc8e1e6a8b6a56311c6f344@kernel.crashing.org> (raw)
In-Reply-To: <20110527103334.GA4236@brick.ozlabs.ibm.com>
>>> I do the check there because I was having problems where, if the HDEC
>>> goes negative before we do the partition switch, we would
>>> occasionally
>>> not get the HDEC interrupt at all until the next time HDEC went
>>> negative, ~ 8.4 seconds later.
>>
>> Yikes - so HDEC is edge and doesn't even keep the interrupt line up?
>> That sounds like a serious hardware limitation. What if you only use
>> HDEC and it triggers while interrupts are off in a critical section?
>> Is the hardware really that broken?
>
> If HDEC expires when interrupts are off, the HDEC interrupt stays
> pending until interrupts get re-enabled. I'm not sure exactly what
> the conditions are that cause an HDEC interrupt to get lost, but they
> seem to involve at least a partition switch.
On some CPUs, if the top bit of the decrementer is 0 again when you
re-enable
the interrupt, the interrupt is lost (so it is actually
level-triggered).
The arch books talk a bit about this AFAIR.
Segher
next prev parent reply other threads:[~2011-05-27 20:59 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20110511103443.GA2837@brick.ozlabs.ibm.com>
[not found] ` <20110511104456.GK2837@brick.ozlabs.ibm.com>
2011-05-15 21:58 ` [PATCH 10/13] kvm/powerpc: Add support for Book3S processors in hypervisor mode Alexander Graf
2011-05-16 5:58 ` [PATCH 10/13] kvm/powerpc: Add support for Book3S processors in Paul Mackerras
2011-05-17 10:17 ` [PATCH 10/13] kvm/powerpc: Add support for Book3S processors in hypervisor mode Alexander Graf
2011-05-27 10:33 ` [PATCH 10/13] kvm/powerpc: Add support for Book3S processors in Paul Mackerras
2011-05-27 10:43 ` [PATCH 10/13] kvm/powerpc: Add support for Book3S processors in hypervisor mode Alexander Graf
2011-05-27 20:59 ` Segher Boessenkool [this message]
2011-05-27 23:19 ` Alexander Graf
2011-05-28 1:07 ` Segher Boessenkool
2011-05-31 20:26 ` Jimi Xenidis
2011-05-31 22:34 ` Segher Boessenkool
2011-06-01 5:11 ` [PATCH 10/13] kvm/powerpc: Add support for Book3S processors in Paul Mackerras
[not found] ` <764651B6-6DDA-49DC-AA95-52CD86FF82D9@suse.de>
[not found] ` <20110517111536.GC7924@brick.ozlabs.ibm.com>
[not found] ` <14CFAA70-1747-4902-8CC1-4BE924CAD031@suse.de>
[not found] ` <4DD25F10.4030707@redhat.com>
[not found] ` <20110519052246.GA8165@drongo>
2011-05-19 6:01 ` [PATCH 0/13] Hypervisor-mode KVM on POWER7 Alexander Graf
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=b833d9df4fc8e1e6a8b6a56311c6f344@kernel.crashing.org \
--to=segher@kernel.crashing.org \
--cc=agraf@suse.de \
--cc=kvm-ppc@vger.kernel.org \
--cc=kvm@vger.kernel.org \
--cc=linuxppc-dev@ozlabs.org \
--cc=paulus@samba.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox