linux-kernel - Re: [PATCH 1/2] KVM: X86: Fix setup the virt_spin_lock

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Message-ID: <20180326223232.ifaoc3zyjii4gq2f@linux-n805>
Date:   Mon, 26 Mar 2018 15:32:32 -0700
From:   Davidlohr Bueso <dave@...olabs.net>
To:     Wanpeng Li <kernellwp@...il.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Kr??m??? <rkrcmar@...hat.com>,
        Davidlohr Bueso <dbueso@...e.de>
Subject: Re: [PATCH 1/2] KVM: X86: Fix setup the virt_spin_lock_key before
 static key get initialized

On Mon, 26 Mar 2018, Wanpeng Li wrote:

>I didn't see any issue when testing this patch, could you elaborate
>what's the bulky mechanism and how it conflicts with early smp bootup
>stages? In addition, do you mean the xen fix is also not suitable?

I have nothing against your patch (or the xen one for that matter), other than
the fact that both seem like band-aid solutions to being able to move up the jump
label init call. I was actually peddling a similar patch but didn't want to add
the extra callback just for that -- at least xen already had smp_ops.smp_prepare_cpus.

Instead of dropping the patches in -tip (ie: delaying the feature), I have nothing
against these fixes being merged. If a better solution is available later, we can
always move dealing with virt_spin_lock_key back into smp_prepare_boot_cpu().

Also a bit unrelated, but am I correct to assume that KVM_HINTS_DEDICATED can be
used via qemu? I've only been dealing with kernel parameters.

Thanks,
Davidlohr