linux-kernel - [PATCH RFC 5/8] KVM: SVM: fix: Don't return an error for `GHCB_MSR_PSC

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Message-Id: <20230127025237.269680-6-jarkko@profian.com>
Date:   Fri, 27 Jan 2023 02:52:34 +0000
From:   Jarkko Sakkinen <jarkko@...fian.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.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,
        "H. Peter Anvin" <hpa@...or.com>
Cc:     Harald Hoyer <harald@...fian.com>, Tom Dohrmann <erbse.13@....de>,
        Ashish Kalra <ashish.kalra@....com>,
        Michael Roth <michael.roth@....com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Jarkko Sakkinen <jarkko@...fian.com>,
        kvm@...r.kernel.org (open list:KERNEL VIRTUAL MACHINE FOR X86 (KVM/x86)),
        linux-kernel@...r.kernel.org (open list:X86 ARCHITECTURE (32-BIT AND
        64-BIT))
Subject: [PATCH RFC 5/8] KVM: SVM: fix: Don't return an error for `GHCB_MSR_PSC_REQ`

From: Tom Dohrmann <erbse.13@....de>

There's no reason to return an error when encountering an page state change
request (PSC request) because that's normal behaviour on the guest's part.
Instead 0 should be returned to cause a VM exit so that userspace can handle
the page state change request.

Link: https://lore.kernel.org/lkml/Y77J7C2E9Xd1QcmZ@notebook/
Signed-off-by: Tom Dohrmann <erbse.13@....de>
Signed-off-by: Jarkko Sakkinen <jarkko@...fian.com>
---
 arch/x86/kvm/svm/sev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index d76127f1499a..899c78d03c35 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -4068,7 +4068,7 @@ static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)
 		vcpu->run->vmgexit.ghcb_msr = control->ghcb_gpa;
 		vcpu->arch.complete_userspace_io = snp_complete_psc_msr_protocol;
 
-		ret = -1;
+		ret = 0;
 		break;
 	case GHCB_MSR_TERM_REQ: {
 		u64 reason_set, reason_code;
-- 
2.38.1