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Reply-To: alex.popov@linux.com
Subject: Re: [PATCH 1/1] x86/apic: Introduce paravirq irq_domain
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To: Jan Kiszka <jan.kiszka@siemens.com>, Paolo Bonzini <pbonzini@redhat.com>
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        Christoph Hellwig <hch@infradead.org>, Ingo Molnar <mingo@redhat.com>,
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        x86@kernel.org, kvm@vger.kernel.org
From: Alexander Popov <alex.popov@linux.com>
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Date: Thu, 18 Aug 2016 01:58:51 +0300
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On 17.08.2016 17:36, Jan Kiszka wrote:
> On 2016-08-15 14:37, Paolo Bonzini wrote:
>> On 15/08/2016 13:51, Alexander Popov wrote:
>>> It seems to me that the idea of an irq_domain for interrupts injected
>>> by a hypervisor is quite generic.
>>
>> True, but all of Xen, KVM and VMware use PCI devices for this.
> 
> So does Jailhouse. We have to have the code anyway because we need to
> keep Linux alive after taking over control. Thus it is actually easier
> to reuse the same logic for para-virtualized domains (non-root cells).

Hello, Jan! Yes, I see.

I can only say that Xen, KVM, VMware and Jailhouse happily use hypercalls,
which are a valid interface between a hypervisor and its guests.

Positive Technologies hypervisor called Gvandra (named after a big Caucasus
mountain) tries to use only the hypercalls and avoid PCI device emulation
to become slimmer.

Best regards,
Alexander