linux-kernel - [PATCH RFC] KVM: nSVM: remove useless kvm_clear_*

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20210802125634.309874-1-pbonzini@redhat.com>
Date:   Mon,  2 Aug 2021 08:56:34 -0400
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     mlevitsk@...hat.com
Subject: [PATCH RFC] KVM: nSVM: remove useless kvm_clear_*_queue

For an event to be in injected state when nested_svm_vmrun executes,
it must have come from exitintinfo when svm_complete_interrupts ran:

  vcpu_enter_guest
   static_call(kvm_x86_run) -> svm_vcpu_run
    svm_complete_interrupts
     // now the event went from "exitintinfo" to "injected"
   static_call(kvm_x86_handle_exit) -> handle_exit
    svm_invoke_exit_handler
      vmrun_interception
       nested_svm_vmrun

However, no event could have been in exitintinfo before a VMRUN
vmexit.  The code in svm.c is a bit more permissive than the one
in vmx.c:

        if (is_external_interrupt(svm->vmcb->control.exit_int_info) &&
            exit_code != SVM_EXIT_EXCP_BASE + PF_VECTOR &&
            exit_code != SVM_EXIT_NPF && exit_code != SVM_EXIT_TASK_SWITCH &&
            exit_code != SVM_EXIT_INTR && exit_code != SVM_EXIT_NMI)

but in any case, a VMRUN instruction would not even start to execute
during an attempted event delivery.

Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kvm/svm/nested.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 61738ff8ef33..5e13357da21e 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -659,11 +659,6 @@ int nested_svm_vmrun(struct kvm_vcpu *vcpu)
 		goto out;
 	}
 
-
-	/* Clear internal status */
-	kvm_clear_exception_queue(vcpu);
-	kvm_clear_interrupt_queue(vcpu);
-
 	/*
 	 * Since vmcb01 is not in use, we can use it to store some of the L1
 	 * state.
-- 
2.27.0