From: Paolo Bonzini <pbonzini@redhat.com>
To: Steve Rutherford <srutherford@google.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
mtosatti@redhat.com, rkrcmar@redhat.com
Subject: Re: [PATCH 3/4] KVM: i8254: remove unnecessary irqchip_in_kernel check
Date: Thu, 30 Jul 2015 09:25:01 +0200 [thread overview]
Message-ID: <55B9D14D.1040600@redhat.com> (raw)
In-Reply-To: <20150730043645.GF15229@google.com>
On 30/07/2015 06:36, Steve Rutherford wrote:
> On Wed, Jul 29, 2015 at 03:28:57PM +0200, Paolo Bonzini wrote:
>> > The PIT is only created if irqchip_in_kernel returns true, so the
>> > check is superfluous.
> I poked around. Looks to me like the existence of an IOAPIC is not
> checked on the creation of the in-kernel PIT.
You're right, and presumably it's also legal to create the PIT before
KVM_CREATE_IRQCHIP.
> Userspace might limit itself to
> that scenario (PIT implies IOAPIC in-kernel), but that isn't enforced at PIT
> creation.
I'll play with the "PIT without IOAPIC" scenario and see if something
breaks badly with this patch. From reading the code it seems like it
should not introduce any problems (oopses or similar), but I'll set this
patch aside for now.
Paolo
next prev parent reply other threads:[~2015-07-30 7:25 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-29 13:28 [PATCH 0/4] KVM: cleanups around memory barriers and irqchip_in_kernel Paolo Bonzini
2015-07-29 13:28 ` [PATCH 1/4] KVM: x86: remove unnecessary memory barriers for shared MSRs Paolo Bonzini
2015-07-29 13:28 ` [PATCH 2/4] KVM: document memory barriers for kvm->vcpus/kvm->online_vcpus Paolo Bonzini
2015-07-30 11:40 ` Christian Borntraeger
2015-07-30 12:46 ` Paolo Bonzini
2015-07-30 13:57 ` Christian Borntraeger
2015-07-30 14:02 ` Paolo Bonzini
2015-07-30 14:05 ` Christian Borntraeger
2015-07-29 13:28 ` [PATCH 3/4] KVM: i8254: remove unnecessary irqchip_in_kernel check Paolo Bonzini
2015-07-30 4:36 ` Steve Rutherford
2015-07-30 7:25 ` Paolo Bonzini [this message]
2015-07-29 13:28 ` [PATCH 4/4] KVM: x86: clean/fix memory barriers in irqchip_in_kernel Paolo Bonzini
2015-07-30 3:32 ` Steve Rutherford
2015-07-30 7:26 ` Paolo Bonzini
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