linux-kernel - Re: [PATCH 6/9] KVM: SVM: WARN if KVM attempts emulation on #UD or #GP for SEV guests

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Message-ID: <23c80e45-856c-b188-44a4-08a97d5e5ba3@redhat.com>
Date:   Tue, 25 Jan 2022 15:56:22 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Liam Merwick <liam.merwick@...cle.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Tom Lendacky <thomas.lendacky@....com>,
        Brijesh Singh <brijesh.singh@....com>
Subject: Re: [PATCH 6/9] KVM: SVM: WARN if KVM attempts emulation on #UD or
 #GP for SEV guests

On 1/20/22 18:04, Sean Christopherson wrote:
>>> +	WARN_ON_ONCE(emul_type & (EMULTYPE_TRAP_UD | EMULTYPE_VMWARE_GP));
>> What about EMULTYPE_TRAP_UD_FORCED?
> Hmm, yeah, it's worth adding, there's no additional cost.  I was thinking it was
> a modifier to EMULTYPE_TRAP_UD, but it's a replacement specifically to bypass
> the EmulateOnUD check (which I should have remembered since I added the type...).
> 

Added on top:

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index d5fe71862bcb..85bbfba1fa07 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4269,7 +4269,9 @@ static bool svm_can_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type,
  		return true;
  
  	/* #UD and #GP should never be intercepted for SEV guests. */
-	WARN_ON_ONCE(emul_type & (EMULTYPE_TRAP_UD | EMULTYPE_VMWARE_GP));
+	WARN_ON_ONCE(emul_type & (EMULTYPE_TRAP_UD |
+				  EMULTYPE_TRAP_UD_FORCED |
+				  EMULTYPE_VMWARE_GP));
  
  	/*
  	 * Emulation is impossible for SEV-ES guests as KVM doesn't have access


Paolo