linux-kernel - Re: [PATCH 1/1] x86/apic: Introduce paravirq irq

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Date:   Fri, 19 Aug 2016 06:47:11 -0400
From:   Jan Kiszka <jan.kiszka@...mens.com>
To:     alex.popov@...ux.com, Paolo Bonzini <pbonzini@...hat.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Christoph Hellwig <hch@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Marc Zyngier <marc.zyngier@....com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Jiang Liu <jiang.liu@...ux.intel.com>,
        Jason Cooper <jason@...edaemon.net>,
        Radim Krcmar <rkrcmar@...hat.com>,
        Joerg Roedel <joro@...tes.org>, linux-kernel@...r.kernel.org,
        x86@...nel.org, kvm@...r.kernel.org
Subject: Re: [PATCH 1/1] x86/apic: Introduce paravirq irq_domain

On 2016-08-17 18:58, Alexander Popov wrote:
> 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.

[Hmm, naming something that's supposed to be slim after something that's
rather big...]

BTW, is there a user of this interface already publicly available? You
didn't reference anything in your posting. Generally, infrastructure
extensions without in-tree users aren't well received (in the best case).

Jan

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