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Date: Fri, 11 Nov 2022 15:23:13 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Paolo Bonzini <pbonzini@...hat.com>
Cc: "Li, Xin3" <xin3.li@...el.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"x86@...nel.org" <x86@...nel.org>,
"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
"tglx@...utronix.de" <tglx@...utronix.de>,
"mingo@...hat.com" <mingo@...hat.com>,
"bp@...en8.de" <bp@...en8.de>,
"dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
"hpa@...or.com" <hpa@...or.com>,
"Christopherson,, Sean" <seanjc@...gle.com>,
"Tian, Kevin" <kevin.tian@...el.com>
Subject: Re: [RESEND PATCH 5/6] KVM: x86/VMX: add kvm_vmx_reinject_nmi_irq()
for NMI/IRQ reinjection
On Fri, Nov 11, 2022 at 01:48:26PM +0100, Paolo Bonzini wrote:
> On 11/11/22 13:19, Peter Zijlstra wrote:
> > On Fri, Nov 11, 2022 at 01:04:27PM +0100, Paolo Bonzini wrote:
> > > On Intel you can optionally make it hold onto IRQs, but NMIs are always
> > > eaten by the VMEXIT and have to be reinjected manually.
> >
> > That 'optionally' thing worries me -- as in, KVM is currently
> > opting-out?
>
> Yes, because "If the “process posted interrupts” VM-execution control is 1,
> the “acknowledge interrupt on exit” VM-exit control is 1" (SDM 26.2.1.1,
> checks on VM-Execution Control Fields). Ipse dixit. Posted interrupts are
> available and used on all processors since I think Ivy Bridge.
(imagine the non-coc compliant reaction here)
So instead of fixing it, they made it worse :-(
And now FRED is arguably making it worse again, and people wonder why I
hate virt...
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