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From: Alexander Graf <agraf@suse.de>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Michael Ellerman <michael@ellerman.id.au>,
	Paul Mackerras <paulus@samba.org>,
	"qemu-ppc@nongnu.org list:PowerPC" <qemu-ppc@nongnu.org>,
	qemu-devel qemu-devel <qemu-devel@nongnu.org>,
	David Gibson <david@gibson.dropbear.id.au>
Subject: Re: [Qemu-devel] [PATCH 5/5] pseries: Move XICS initialization before cpu initialization
Date: Sat, 16 Mar 2013 07:07:30 +0100	[thread overview]
Message-ID: <3B6E68DC-2ADF-4801-A859-4005C5750557@suse.de> (raw)
In-Reply-To: <1363412487.1244.21.camel@pasglop>



Am 16.03.2013 um 06:41 schrieb Benjamin Herrenschmidt <benh@kernel.crashing.org>:

> On Sat, 2013-03-16 at 06:33 +0100, Alexander Graf wrote:
>>>> We're changing that notion in the in-kernel XICS discussions.  The
>> flow will look like this:
>>>> 
>>>> * create vcpus
>>>> * create XICS
>>>> * foreach (vcpu)
>>>>     * enable_cap(vcpu, CAP_XICS_SERVER, xics_handle)
>>> 
>>> This is stupid. Why have the VCPU initialize itself for non-kernel
>>> interrupts and *then* switch it over ?
>> 
>> Because non-kernel initialization is a nop.
> 
> And ?

Compared to the previous aproach of a vm wide irq type, we win:

  - less vm global state
  - possibility of defining the 'cpu nr' from the pic's point of view
  - the same mechanism and code paths for hotplug and non-hotplug
  - possibility of supporting multiple pics
  - less implicit assumptions

While the code changes required to make this work should be minimal over the "set irq architecture" approach. It really makes life easier for everyone.


Alex

  reply	other threads:[~2013-03-16  6:07 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-03-14  1:53 [Qemu-devel] [0/5] Assorted pending pseries machine patches David Gibson
2013-03-14  1:53 ` [Qemu-devel] [PATCH 1/5] target-ppc: Synchronize VPA state with KVM David Gibson
2013-03-15 12:22   ` Alexander Graf
2013-04-08  5:01     ` [Qemu-devel] [Qemu-ppc] " David Gibson
2013-03-14  1:53 ` [Qemu-devel] [PATCH 2/5] pseries: Remove "busname" property for PCI host bridge David Gibson
2013-03-15 12:39   ` Alexander Graf
2013-03-14  1:53 ` [Qemu-devel] [PATCH 3/5] pseries: Fixes and enhancements to L1 cache properties David Gibson
2013-03-15 12:27   ` Alexander Graf
2013-03-16  7:10     ` [Qemu-devel] [Qemu-ppc] " David Gibson
2013-03-18 11:10       ` Andreas Färber
2013-03-19  0:52         ` David Gibson
2013-03-18 10:54     ` [Qemu-devel] " Andreas Färber
2013-03-18 11:05       ` Alexander Graf
2013-03-19 11:06         ` Andreas Färber
2013-03-19 11:09           ` Alexander Graf
2013-03-19 11:16             ` Andreas Färber
2013-03-19 11:37               ` Alexander Graf
2013-03-19  1:00       ` [Qemu-devel] [Qemu-ppc] " David Gibson
2013-03-19 10:10         ` Alexander Graf
2013-03-14  1:53 ` [Qemu-devel] [PATCH 4/5] target-ppc: Remove CONFIG_PSERIES dependency in kvm.c David Gibson
2013-03-15 12:39   ` Alexander Graf
2013-03-14  1:53 ` [Qemu-devel] [PATCH 5/5] pseries: Move XICS initialization before cpu initialization David Gibson
2013-03-15 12:33   ` Alexander Graf
2013-03-16  3:14     ` Benjamin Herrenschmidt
2013-03-16  5:33       ` Alexander Graf
2013-03-16  5:41         ` Benjamin Herrenschmidt
2013-03-16  6:07           ` Alexander Graf [this message]
2013-03-18  2:55     ` [Qemu-devel] [Qemu-ppc] " David Gibson
2013-03-18  3:12       ` Alexander Graf
2013-03-18  3:38         ` David Gibson
2013-03-21 10:01           ` Alexander Graf

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