Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Fri, 11 Nov 2022 13:19:31 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Paolo Bonzini <pbonzini@redhat.com>
Cc:     "Li, Xin3" <xin3.li@intel.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "x86@kernel.org" <x86@kernel.org>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "tglx@linutronix.de" <tglx@linutronix.de>,
        "mingo@redhat.com" <mingo@redhat.com>,
        "bp@alien8.de" <bp@alien8.de>,
        "dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
        "hpa@zytor.com" <hpa@zytor.com>,
        "Christopherson,, Sean" <seanjc@google.com>,
        "Tian, Kevin" <kevin.tian@intel.com>
Subject: Re: [RESEND PATCH 5/6] KVM: x86/VMX: add kvm_vmx_reinject_nmi_irq()
 for NMI/IRQ reinjection
Message-ID: <Y24908NWCdzUNqI0@hirez.programming.kicks-ass.net>
References: <20221110061545.1531-1-xin3.li@intel.com>
 <20221110061545.1531-6-xin3.li@intel.com>
 <Y2y+YgBUYuUHbPtd@hirez.programming.kicks-ass.net>
 <BN6PR1101MB2161976800EB14B74A24D9F3A8019@BN6PR1101MB2161.namprd11.prod.outlook.com>
 <Y24SoNKZtj/NPSGy@hirez.programming.kicks-ass.net>
 <6097036e-063f-5175-72b2-8935b12af853@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <6097036e-063f-5175-72b2-8935b12af853@redhat.com>
Precedence: bulk

On Fri, Nov 11, 2022 at 01:04:27PM +0100, Paolo Bonzini wrote:
> On 11/11/22 10:15, Peter Zijlstra wrote:
> > I don't speak virt (but this all sounds disguisting)
> 
> Yes, it is.  AMD does not need this, they just hold onto the interrupt
> until the host has issued both STGI (for NMIs) and STI (for IRQs).

Right -- Cooper just explained that to me.

> 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?

Since much of this is about preparing for FRED, can we pretty *PLEASE*
fix this VMX NMI hole instead so that all this nonsense isn't needed
anymore, please, really please?

Have FRED imply a GI flag for VMX or something and then we can all
forget about these reinjection horrors.