From: Sean Christopherson <seanjc@google.com>
To: Chao Gao <chao.gao@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Andrew Cooper <Andrew.Cooper3@citrix.com>,
Kai Huang <kai.huang@intel.com>
Subject: Re: [PATCH v2 03/18] x86/reboot: Harden virtualization hooks for emergency reboot
Date: Mon, 13 Mar 2023 10:08:37 -0700 [thread overview]
Message-ID: <ZA9YlTknLKRKcCy3@google.com> (raw)
In-Reply-To: <ZA7eTpG5tpo5yIo3@gao-cwp>
On Mon, Mar 13, 2023, Chao Gao wrote:
> On Fri, Mar 10, 2023 at 01:42:17PM -0800, Sean Christopherson wrote:
> >+void cpu_emergency_register_virt_callback(cpu_emergency_virt_cb *callback)
> >+{
> >+ if (WARN_ON_ONCE(rcu_access_pointer(cpu_emergency_virt_callback)))
> >+ return;
> >+
> >+ rcu_assign_pointer(cpu_emergency_virt_callback, callback);
>
> Was it intentional to not call synchronize_rcu() (in the original
> code), different from the un-registration path?
Yes, synchronize_rcu() is needed when removing a callback to ensure any in-flight
invocations of the callback complete before KVM is unloaded, i.e. to prevent
use-after-free of the KVM module code. Registering a callback doesn't have the
same concerns, and adding a synchronize_rcu() wouldn't do anything in terms of
ensuring virtualization isn't enabled after an emergency restart/shutdown is
initiated.
next prev parent reply other threads:[~2023-03-13 17:10 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-10 21:42 [PATCH v2 00/18] x86/reboot: KVM: Clean up "emergency" virt code Sean Christopherson
2023-03-10 21:42 ` [PATCH v2 01/18] x86/reboot: VMCLEAR active VMCSes before emergency reboot Sean Christopherson
2023-03-10 21:42 ` [PATCH v2 02/18] x86/reboot: Expose VMCS crash hooks if and only if KVM_INTEL is enabled Sean Christopherson
2023-03-13 0:31 ` Huang, Kai
2023-03-13 18:31 ` Sean Christopherson
2023-03-14 1:19 ` Huang, Kai
2023-03-10 21:42 ` [PATCH v2 03/18] x86/reboot: Harden virtualization hooks for emergency reboot Sean Christopherson
2023-03-13 8:26 ` Chao Gao
2023-03-13 17:08 ` Sean Christopherson [this message]
2023-03-10 21:42 ` [PATCH v2 04/18] x86/reboot: KVM: Handle VMXOFF in KVM's reboot callback Sean Christopherson
2023-03-10 21:42 ` [PATCH v2 05/18] x86/reboot: KVM: Disable SVM during reboot via virt/KVM " Sean Christopherson
2023-03-13 0:52 ` Huang, Kai
2023-03-13 17:18 ` Sean Christopherson
2023-03-14 0:42 ` Huang, Kai
2023-03-15 0:47 ` Sean Christopherson
2023-03-15 1:30 ` Huang, Kai
2023-03-10 21:42 ` [PATCH v2 06/18] x86/reboot: Hoist "disable virt" helpers above "emergency reboot" path Sean Christopherson
2023-03-10 21:42 ` [PATCH v2 07/18] x86/reboot: Disable virtualization during reboot iff callback is registered Sean Christopherson
2023-03-13 0:54 ` Huang, Kai
2023-03-13 18:40 ` Sean Christopherson
2023-03-14 0:50 ` Huang, Kai
2023-03-10 21:42 ` [PATCH v2 08/18] x86/reboot: Assert that IRQs are disabled when turning off virtualization Sean Christopherson
2023-03-10 21:42 ` [PATCH v2 09/18] x86/virt: KVM: Open code cpu_has_vmx() in KVM VMX Sean Christopherson
2023-03-10 21:42 ` [PATCH v2 10/18] x86/virt: KVM: Move VMXOFF helpers into " Sean Christopherson
2023-03-10 21:42 ` [PATCH v2 11/18] KVM: SVM: Make KVM_AMD depend on CPU_SUP_AMD or CPU_SUP_HYGON Sean Christopherson
2023-03-10 21:42 ` [PATCH v2 12/18] x86/virt: Drop unnecessary check on extended CPUID level in cpu_has_svm() Sean Christopherson
2023-03-10 21:42 ` [PATCH v2 13/18] x86/virt: KVM: Open code cpu_has_svm() into kvm_is_svm_supported() Sean Christopherson
2023-03-10 21:42 ` [PATCH v2 14/18] KVM: SVM: Check that the current CPU supports SVM in kvm_is_svm_supported() Sean Christopherson
2023-03-13 2:47 ` Huang, Kai
2023-03-13 17:29 ` Sean Christopherson
2023-03-14 0:17 ` Huang, Kai
2023-03-10 21:42 ` [PATCH v2 15/18] KVM: VMX: Ensure CPU is stable when probing basic VMX support Sean Christopherson
2023-03-10 21:42 ` [PATCH v2 16/18] x86/virt: KVM: Move "disable SVM" helper into KVM SVM Sean Christopherson
2023-03-10 21:42 ` [PATCH v2 17/18] KVM: x86: Force kvm_rebooting=true during emergency reboot/crash Sean Christopherson
2023-03-10 21:42 ` [PATCH v2 18/18] KVM: SVM: Use "standard" stgi() helper when disabling SVM Sean Christopherson
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