From: cmetcalf@ezchip•com (Chris Metcalf)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] help guest boot up on AArch64 host with GICv2
Date: Fri, 15 Jan 2016 15:02:48 -0500 [thread overview]
Message-ID: <56995068.9050207@ezchip.com> (raw)
We are using GICv2 compatibility mode in the Fast Models/Foundation
Models simulations we are running because the boot code (ATF/UEFI)
doesn't support GICv3 in our system at the moment.
However, starting with kernel 4.2, the guest couldn't boot up because it
wasn't getting timer interrupts. I tracked this down to a kernel commit
that switched to using the "alternatives" mechanism -- rather than
seeing either a GICv2 or GICv3 and configuring appropriately, the KVM
code just configured the code that saves/restores the vgic state based
on the presence of the system register interface to the GIC CPU
interface. See the attached patch for a fix that manages this
differently and allows me to boot up the guest in this configuration.
However, even assuming this patch can be taken into an upstream tree, I
still have a couple of additional problems:
- I can boot up with the Foundation Models using this change, but not
with the Fast Models (again, using a v3 GIC but in v2 compatibility mode
in the device tree). The Fast Models dts looks like it has the same
configuration for the GIC and the timers so I'm not sure what's going on
here. Any suggestions appreciated.
- Without this change, I could only boot kernels up to 4.1. With the
change, I can boot kernels up to 4.3. But 4.4 won't boot for me either;
I haven't bisected it down yet. So any suggestions on what might be
going wrong here would also be appreciated.
We are planning to eventually use GICv3 mode in our software stack but
for the time being I assume it is interesting to resolve issues with GIC
v2 compatibility mode on GIC v3.
--
Chris Metcalf, EZChip Semiconductor
http://www.ezchip.com
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next reply other threads:[~2016-01-15 20:02 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-15 20:02 Chris Metcalf [this message]
2016-01-18 9:28 ` [PATCH] help guest boot up on AArch64 host with GICv2 Marc Zyngier
2016-01-26 20:43 ` Chris Metcalf
2016-01-27 9:12 ` Marc Zyngier
2016-01-28 20:12 ` Chris Metcalf
2016-01-29 7:24 ` Ard Biesheuvel
2016-01-29 17:49 ` Chris Metcalf
2016-01-29 17:54 ` Marc Zyngier
2016-01-29 18:29 ` Chris Metcalf
2016-01-29 18:55 ` Marc Zyngier
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