Am 03.01.2017 um 17:12 schrieb Paolo Bonzini:
On 03/01/2017 14:04, David Hildenbrand wrote:
Am 16.12.2016 um 16:10 schrieb Radim Krčmář:
We don't treat kvm->arch.vpic specially anymore, so the setup can look
like ioapic. This gets a bit more information out of return values.
This originally saved us from a race condition as far as I can
reconstruct from the commit history. Think the problem was
vpic being set but routes not being set up yet.
commit 71ba994c94a81c37185ef2fb5190844286ba9aca
Author: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Date: Wed Jul 29 12:31:15 2015 +0200
KVM: x86: clean/fix memory barriers in irqchip_in_kernel
The memory barriers are trying to protect against concurrent RCU-based
interrupt injection, but the IRQ routing table is not valid at the time
kvm->arch.vpic is written. Fix this by writing kvm->arch.vpic last.
kvm_destroy_pic then need not set kvm->arch.vpic to NULL; modify it
to take a struct kvm_pic* and reuse it if the IOAPIC creation fails.
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
I assume that this is now fixed via the irqchip_mode, as it is stored
last? If so, I really like this patch :)
Yes, the previous patch referred to that when it said
"irqchip_in_kernel() tried to save a bit by reusing pic_irqchip()", and
what this commit message means by "not trteating kvm->arch.vpic
specially anymore".
Thanks for confirming!
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Paolo
--
David
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