linux-kernel - Re: [PATCH v4 00/19] x86/reboot: KVM: Clean up "emergency" virt code

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Message-ID: <169110224628.1966361.853135096516007767.b4-ty@google.com>
Date:   Thu,  3 Aug 2023 17:40:26 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Andrew Cooper <Andrew.Cooper3@...rix.com>,
        Kai Huang <kai.huang@...el.com>, Chao Gao <chao.gao@...el.com>
Subject: Re: [PATCH v4 00/19] x86/reboot: KVM: Clean up "emergency" virt code

On Fri, 21 Jul 2023 13:18:40 -0700, Sean Christopherson wrote:
> If there are no objections, my plan is to take this through the KVM tree
> for 6.6.
> 
> Instead of having the reboot code blindly try to disable virtualization
> during an emergency, use the existing callback into KVM to disable virt
> as "needed".  In quotes because KVM still somewhat blindly attempts to
> disable virt, e.g. if KVM is loaded but doesn't have active VMs and thus
> hasn't enabled hardware.  That could theoretically be "fixed", but due to
> the callback being invoked from NMI context, I'm not convinced it would
> be worth the complexity.  E.g. false positives would still be possible,
> and KVM would have to play games with the per-CPU hardware_enabled flag
> to ensure there are no false negatives.
> 
> [...]

Applied to kvm-x86 misc, thanks!

[01/19] x86/reboot: VMCLEAR active VMCSes before emergency reboot
        https://github.com/kvm-x86/linux/commit/b23c83ad2c63
[02/19] x86/reboot: Harden virtualization hooks for emergency reboot
        https://github.com/kvm-x86/linux/commit/5e408396c60c
[03/19] x86/reboot: KVM: Handle VMXOFF in KVM's reboot callback
        https://github.com/kvm-x86/linux/commit/119b5cb4ffd0
[04/19] x86/reboot: KVM: Disable SVM during reboot via virt/KVM reboot callback
        https://github.com/kvm-x86/linux/commit/baeb4de7ad12
[05/19] x86/reboot: Assert that IRQs are disabled when turning off virtualization
        https://github.com/kvm-x86/linux/commit/ad93c1a7c010
[06/19] x86/reboot: Hoist "disable virt" helpers above "emergency reboot" path
        https://github.com/kvm-x86/linux/commit/edc8deb087d8
[07/19] x86/reboot: Disable virtualization during reboot iff callback is registered
        https://github.com/kvm-x86/linux/commit/59765db5fc82
[08/19] x86/reboot: Expose VMCS crash hooks if and only if KVM_{INTEL,AMD} is enabled
        https://github.com/kvm-x86/linux/commit/261cd5ed934e
[09/19] x86/virt: KVM: Open code cpu_has_vmx() in KVM VMX
        https://github.com/kvm-x86/linux/commit/b6a6af0d19ce
[10/19] x86/virt: KVM: Move VMXOFF helpers into KVM VMX
        https://github.com/kvm-x86/linux/commit/22e420e12739
[11/19] KVM: SVM: Make KVM_AMD depend on CPU_SUP_AMD or CPU_SUP_HYGON
        https://github.com/kvm-x86/linux/commit/554856b69e3d
[12/19] x86/virt: Drop unnecessary check on extended CPUID level in cpu_has_svm()
        https://github.com/kvm-x86/linux/commit/5df8ecfe3632
[13/19] x86/virt: KVM: Open code cpu_has_svm() into kvm_is_svm_supported()
        https://github.com/kvm-x86/linux/commit/85fd29dd5fe4
[14/19] KVM: SVM: Check that the current CPU supports SVM in kvm_is_svm_supported()
        https://github.com/kvm-x86/linux/commit/c4db4f20f3bf
[15/19] KVM: VMX: Ensure CPU is stable when probing basic VMX support
        https://github.com/kvm-x86/linux/commit/f9a8866040fc
[16/19] x86/virt: KVM: Move "disable SVM" helper into KVM SVM
        https://github.com/kvm-x86/linux/commit/76ab8161083b
[17/19] KVM: x86: Force kvm_rebooting=true during emergency reboot/crash
        https://github.com/kvm-x86/linux/commit/6ae44e012f4c
[18/19] KVM: SVM: Use "standard" stgi() helper when disabling SVM
        https://github.com/kvm-x86/linux/commit/2e6b9bd49b70
[19/19] KVM: VMX: Skip VMCLEAR logic during emergency reboots if CR4.VMXE=0
        https://github.com/kvm-x86/linux/commit/a788fbb763b5

--
https://github.com/kvm-x86/linux/tree/next
https://github.com/kvm-x86/linux/tree/fixes