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AFNElJ9tCZy3AtofOVw7npuu+pMO9Z8Itl0DZFffK3GkqISQArYz9ClUfdroX2sRdbXTCzzXcU0=@vger.kernel.org X-Gm-Message-State: AOJu0YwH/wyKu7NOCLLu8IGUzePo1A84vlPXHFLmdijF3l+fDnd+LSAM p+Om6gX5eqo+clcioPdnDbh07s8szFIDP6GB0LOm9iNyx+kJ4FpDnN8ZRYgJkAIDWGIWBgDdwX9 rtJlA+A== X-Received: from pgbbw30.prod.google.com ([2002:a05:6a02:49e:b0:c80:2541:2de8]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a20:9151:b0:3a3:a5cd:560d with SMTP id adf61e73a8af0-3b22e7c65ffmr19983378637.9.1779199561253; Tue, 19 May 2026 07:06:01 -0700 (PDT) Date: Tue, 19 May 2026 07:06:00 -0700 In-Reply-To: Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260514213115.1637082-1-seanjc@google.com> <20260514213115.1637082-3-seanjc@google.com> Message-ID: Subject: Re: [PATCH v3 2/3] KVM: SVM: Disable x2AVIC RDMSR interception for MSRs KVM actually supports From: Sean Christopherson To: Naveen N Rao Cc: Paolo Bonzini , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="us-ascii" On Fri, May 15, 2026, Naveen N Rao wrote: > On Thu, May 14, 2026 at 02:31:14PM -0700, Sean Christopherson wrote: > > When toggling x2AVIC on/off, use KVM's curated mask of x2APIC MSRs that > > can/should be passed through to the guest (or not) when 2AVIC is enabled. > > Using the effective list provided by the local APIC emulation fixes > > multiple (classes of) bugs, as the existing hand-coded list of MSRs is > > wrong on multiple fronts: > > > > - ARBPRI isn't supported by x2APIC, but its unaccelerated AVIC intercept > > is fault-like; disabling interception is nonsensical and suboptimal as > > the access generates a #VMEXIT that requires decoding the instruction. > > Nit: unless you decided against incorporating the changes we discussed > in v2, please update this part while applying. Gah, I just spaced it. I'll reword to: - ARBPRI isn't supported by KVM, isn't accelerated by AVIC (for read or write), and its #VMEXIT is fault-like, i.e. requires decoding the instruction. Disabling interception is nonsensical and suboptimal.