From: Naveen N Rao <naveen@kernel.org>
To: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Sean Christopherson <seanjc@google.com>,
Borislav Petkov <bp@alien8.de>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Paolo Bonzini <pbonzini@redhat.com>,
Nikunj A Dadhania <nikunj@amd.com>,
Neeraj Upadhyay <neeraj.upadhyay@amd.com>,
Tianyu Lan <tiala@microsoft.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Thomas Gleixner <tglx@kernel.org>
Subject: Re: [RFC PATCH v3 03/27] x86/kvm: Disable PV_SEND_IPI if Secure AVIC is enabled
Date: Tue, 14 Jul 2026 15:12:57 +0530 [thread overview]
Message-ID: <alX7QbNjf7FkXVRR@blrnaveerao1> (raw)
In-Reply-To: <c2712047-cf0d-43de-be42-fa7ae80277a4@amd.com>
On Mon, Jul 13, 2026 at 12:52:06PM -0500, Tom Lendacky wrote:
> On 7/8/26 01:32, Naveen N Rao (AMD) wrote:
> > In Secure AVIC mode, Linux does not allow IPIs to be injected as the
> > hypervisor is untrusted. This is achieved by not setting the IPI vector
> > in SAVIC_ALLOWED_IRR in the Secure AVIC guest APIC Backing page. Due to
> > this, PV_SEND_IPI cannot work since it needs KVM to be able to inject
> > IPIs into the guest. Disable the same.
>
> Another guest patch...
>
> Does this have an impact on the hypervisor? Is the injected IPI just
> ignored because of the SAVIC_ALLOWED_IRR? How would the hypervisor know
> that it needs to schedule the target vCPU if not using this, a write to
> the ICR?
No impact on the hypervisor. Previous KVM implementation relied on
disabling these at the hypervisor level, which is ok too. But, this
really should be a guest policy since PV_SEND_IPI can work if the guest
chooses to allow IPIs (via SAVIC_ALLOWED_IRR).
In the absence of this, guest will use the regular IPI path and go
through the savic driver, which will do a SVM_EXIT_MSR VMGEXIT to
request hypervisor assistance for IPI delivery.
- Naveen
next prev parent reply other threads:[~2026-07-14 9:51 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-08 6:31 [RFC PATCH v3 00/27] KVM: SVM: Add support for SEV-SNP Secure AVIC Naveen N Rao (AMD)
2026-07-08 6:31 ` [RFC PATCH v3 01/27] x86/apic: Propagate APIC_SPIV writes to hv for " Naveen N Rao (AMD)
2026-07-10 2:03 ` Borislav Petkov
2026-07-10 15:02 ` Naveen N Rao
2026-07-11 4:37 ` Borislav Petkov
2026-07-13 17:38 ` Tom Lendacky
2026-07-14 8:57 ` Naveen N Rao
2026-07-08 6:32 ` [RFC PATCH v3 02/27] x86/apic: Drop savic_eoi() in favor of native_apic_msr_eoi() " Naveen N Rao (AMD)
2026-07-13 17:43 ` Tom Lendacky
2026-07-14 9:02 ` Naveen N Rao
2026-07-08 6:32 ` [RFC PATCH v3 03/27] x86/kvm: Disable PV_SEND_IPI if Secure AVIC is enabled Naveen N Rao (AMD)
2026-07-13 17:52 ` Tom Lendacky
2026-07-14 9:42 ` Naveen N Rao [this message]
2026-07-08 6:32 ` [RFC PATCH v3 04/27] x86/apic: Use AVIC_INCOMPLETE_IPI VMGEXIT for Secure AVIC IPI handling Naveen N Rao (AMD)
2026-07-13 17:59 ` Tom Lendacky
2026-07-14 10:03 ` Naveen N Rao
2026-07-08 6:32 ` [RFC PATCH v3 05/27] x86/cpufeatures: Add Secure AVIC CPU feature Naveen N Rao (AMD)
2026-07-13 18:32 ` Tom Lendacky
2026-07-08 6:32 ` [RFC PATCH v3 06/27] KVM: SVM: Add helper to check if Secure AVIC is enabled for a guest Naveen N Rao (AMD)
2026-07-13 18:35 ` Tom Lendacky
2026-07-08 6:32 ` [RFC PATCH v3 07/27] KVM: SVM: Set guest_apic_protected if Secure AVIC is enabled Naveen N Rao (AMD)
2026-07-08 6:32 ` [RFC PATCH v3 08/27] kvm: irqfd: Have kvm_arch_has_irq_bypass() take struct kvm pointer Naveen N Rao (AMD)
2026-07-08 6:32 ` [RFC PATCH v3 09/27] KVM: SVM: Disable IRQ bypass for Secure AVIC Naveen N Rao (AMD)
2026-07-08 6:32 ` [RFC PATCH v3 10/27] KVM: SVM: Add avic_ipiv_is_soft_disabled() as a wrapper around enable_ipiv Naveen N Rao (AMD)
2026-07-08 6:32 ` [RFC PATCH v3 11/27] KVM: SVM: Disable IPIv for Secure AVIC Naveen N Rao (AMD)
2026-07-08 6:32 ` [RFC PATCH v3 12/27] KVM: SVM: Short-circuit a few AVIC flows " Naveen N Rao (AMD)
2026-07-08 6:32 ` [RFC PATCH v3 13/27] KVM: SVM: Warn if we ever receive AVIC_UNACCELERATED_ACCESS #VMEXIT Naveen N Rao (AMD)
2026-07-08 6:32 ` [RFC PATCH v3 14/27] KVM: SVM: Do not inhibit AVIC for SEV-SNP guests if Secure AVIC is enabled Naveen N Rao (AMD)
2026-07-08 6:32 ` [RFC PATCH v3 15/27] KVM: SVM: Set VGIF in VMSA area for Secure AVIC guests Naveen N Rao (AMD)
2026-07-08 6:32 ` [RFC PATCH v3 16/27] KVM: SVM: Add handler for VMGEXIT Secure AVIC NAE event Naveen N Rao (AMD)
2026-07-08 6:32 ` [RFC PATCH v3 17/27] KVM: SVM: Do not intercept SECURE_AVIC_CONTROL MSR for Secure AVIC guests Naveen N Rao (AMD)
2026-07-08 6:32 ` [RFC PATCH v3 18/27] KVM: x86: Add a new kvm_x86_op protected_apic_has_injectable_intr() Naveen N Rao (AMD)
2026-07-08 6:32 ` [RFC PATCH v3 19/27] KVM: SVM: Implement kvm_x86_ops->protected_apic_has_injectable_intr() for Secure AVIC Naveen N Rao (AMD)
2026-07-08 6:32 ` [RFC PATCH v3 20/27] KVM: SVM: Implement kvm_x86_ops->protected_apic_has_interrupt() " Naveen N Rao (AMD)
2026-07-08 6:32 ` [RFC PATCH v3 21/27] KVM: SVM: Add interrupt delivery support for Secure AVIC guests Naveen N Rao (AMD)
2026-07-08 6:32 ` [RFC PATCH v3 22/27] KVM: SVM: Add support for incomplete IPI handling for Secure AVIC Naveen N Rao (AMD)
2026-07-08 6:32 ` [RFC PATCH v3 23/27] KVM: SVM: Add support for injecting NMIs for Secure AVIC guests Naveen N Rao (AMD)
2026-07-08 6:32 ` [RFC PATCH v3 24/27] KVM: SVM: Mandate use of split irqchip for Secure AVIC Naveen N Rao (AMD)
2026-07-08 6:32 ` [RFC PATCH v3 25/27] KVM: SVM: Do not inject exceptions " Naveen N Rao (AMD)
2026-07-08 6:32 ` [RFC PATCH v3 26/27] KVM: SVM: Do not intercept exceptions for Secure AVIC guests Naveen N Rao (AMD)
2026-07-08 6:32 ` [RFC PATCH v3 27/27] KVM: SVM: Advertise Secure AVIC support for SEV-SNP guests Naveen N Rao (AMD)
2026-07-08 9:20 ` [RFC PATCH v3 00/27] KVM: SVM: Add support for SEV-SNP Secure AVIC Naveen N Rao
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