linux-kernel - RE: Any standard kernel API to dynamically allocate/free per-cpu vectors on x86?

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 4 Apr 2018 23:30:38 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     Thomas Gleixner <tglx@...utronix.de>
CC:     'Greg KH' <gregkh@...uxfoundation.org>,
        "Michael Kelley (EOSG)" <Michael.H.Kelley@...rosoft.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        KY Srinivasan <kys@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>
Subject: RE: Any standard kernel API to dynamically allocate/free per-cpu
 vectors on x86?

> From: Thomas Gleixner
> > I'm wondering if there is such a standard kernel API on x86.
> > As I skimmed through the code, I haven't found it yet, if any.
> >
> We don't have a simple way to do such allocations because they involve IDT
> entry manipulation.

Hi tglx,
Thanks for the quick detailed reply!
 
> If there is no hard requirement that this stuff runs through an direct
> vector, then we could simply make these interrupts go through the normal
> interrupt path. That means you have to request them like regular device
> interrupts and the handling path is slightly longer than the direct vector
> mode. You'd get virtual interrupt numbers per cpu which also show up in
> /proc/interrupts as separate lines.
> 
> That needs a very simple and minimal virtual interrupt controller driver
> which is mostly a dummy implementation except for the activation function
> which would allow you to retrieve the vector number and store it in the
> MSR.

Can you please give a little more guidance? e.g. is there any similar driver,
any pointer to the required APIs, etc. 
I guess I need to dig into stuff like 
struct irq_domain_ops x86_vector_domain_ops and request_percpu_irq().
Your quick pointer would help a lot!

> There are a few details to be hashed out vs. CPU hotplug, but we have all
> the infrastructure in place to deal with that.
Sounds great!

BTW, so far, Hyper-V doesn't support CPU hotplug, but it supports dynamic
CPU online/offline . I guess I must also consider CPU online/offline here.

Thanks
-- Dexuan