From: Paolo Bonzini <pbonzini@redhat.com>
To: Steve Rutherford <srutherford@google.com>
Cc: kvm@vger.kernel.org
Subject: Re: [PATCH v5 4/4] KVM: x86: Add support for local interrupt requests from userspace
Date: Wed, 29 Jul 2015 12:21:01 +0200 [thread overview]
Message-ID: <55B8A90D.3030202@redhat.com> (raw)
In-Reply-To: <20150728190635.GA7460@google.com>
On 28/07/2015 21:06, Steve Rutherford wrote:
>>> > > +static inline int pic_in_kernel(struct kvm *kvm)
>>> > > +{
>>> > > + int ret;
>>> > > +
>>> > > + ret = (pic_irqchip(kvm) != NULL);
>>> > > + smp_rmb();
>> >
>> > What does this memory barrier pair with? I don't think it's necessary.
> To be honest, it's probably not necessary. I couldn't find why
> irqchip_in_kernel (which this function is more or less a copy of)
> needed it's memory barrier, so I cargo culted this one in.
It's for stuff like injecting an interrupt before any CPU is created,
while another thread is doing KVM_CREATE_IRQCHIP. In your case a VCPU
has been created so you don't need it (the synchronization point is the
mutex_lock(&kvm->lock) in kvm_vm_ioctl_create_vcpu).
Paolo
next prev parent reply other threads:[~2015-07-29 10:21 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-27 23:17 [PATCH v5 1/4] KVM: x86: Split the APIC from the rest of IRQCHIP Steve Rutherford
2015-07-27 23:17 ` [PATCH v5 2/4] KVM: x86: Add KVM exit for IOAPIC EOIs Steve Rutherford
2015-07-27 23:17 ` [PATCH v5 3/4] KVM: x86: Add EOI exit bitmap inference Steve Rutherford
2015-07-29 12:38 ` Paolo Bonzini
2015-07-29 20:27 ` Steve Rutherford
2015-07-30 6:23 ` Jan Kiszka
2015-07-30 6:27 ` Steve Rutherford
2015-07-27 23:17 ` [PATCH v5 4/4] KVM: x86: Add support for local interrupt requests from userspace Steve Rutherford
2015-07-28 15:58 ` Paolo Bonzini
2015-07-28 19:06 ` Steve Rutherford
2015-07-28 22:05 ` Paolo Bonzini
2015-07-29 0:50 ` Steve Rutherford
2015-07-29 10:21 ` Paolo Bonzini [this message]
2015-07-29 10:15 ` Paolo Bonzini
2015-07-29 12:56 ` [PATCH v5 1/4] KVM: x86: Split the APIC from the rest of IRQCHIP Paolo Bonzini
2015-07-30 3:04 ` Steve Rutherford
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