linux-kernel - [PATCH] KVM: x86: Only advertise KVM_CAP_READONLY

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Message-Id: <20240902144219.3716974-1-erbse.13@gmx.de>
Date: Mon,  2 Sep 2024 14:42:19 +0000
From: Tom Dohrmann <erbse.13@....de>
To: Tom Dohrmann <erbse.13@....de>
Cc: kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Sean Christopherson <seanjc@...gle.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Michael Roth <michael.roth@....com>
Subject: [PATCH] KVM: x86: Only advertise KVM_CAP_READONLY_MEM when supported by VM

Until recently, KVM_CAP_READONLY_MEM was unconditionally supported on
x86, but this is no longer the case for SEV-ES and SEV-SNP VMs.

When KVM_CHECK_EXTENSION is invoked on a VM, only advertise
KVM_CAP_READONLY_MEM when it's actually supported.

Fixes: 66155de93bcf ("KVM: x86: Disallow read-only memslots for SEV-ES and SEV-SNP (and TDX)")
Cc: Sean Christopherson <seanjc@...gle.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Michael Roth <michael.roth@....com>
Signed-off-by: Tom Dohrmann <erbse.13@....de>
---
 arch/x86/kvm/x86.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 70219e406987..9ad7fe279e72 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4656,7 +4656,6 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_ASYNC_PF_INT:
 	case KVM_CAP_GET_TSC_KHZ:
 	case KVM_CAP_KVMCLOCK_CTRL:
-	case KVM_CAP_READONLY_MEM:
 	case KVM_CAP_IOAPIC_POLARITY_IGNORED:
 	case KVM_CAP_TSC_DEADLINE_TIMER:
 	case KVM_CAP_DISABLE_QUIRKS:
@@ -4815,6 +4814,8 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_VM_TYPES:
 		r = kvm_caps.supported_vm_types;
 		break;
+	case KVM_CAP_READONLY_MEM:
+		r = kvm ? kvm_arch_has_readonly_mem(kvm) : 1;
 	default:
 		break;
 	}
--
2.34.1