From 66570e966dd9cb4fd57811d0056c6472a14a2c41 Mon Sep 17 00:00:00 2001 From: Oliver Upton Date: Tue, 18 Aug 2020 15:24:28 +0000 Subject: kvm: x86: only provide PV features if enabled in guest's CPUID KVM unconditionally provides PV features to the guest, regardless of the configured CPUID. An unwitting guest that doesn't check KVM_CPUID_FEATURES before use could access paravirt features that userspace did not intend to provide. Fix this by checking the guest's CPUID before performing any paravirtual operations. Introduce a capability, KVM_CAP_ENFORCE_PV_FEATURE_CPUID, to gate the aforementioned enforcement. Migrating a VM from a host w/o this patch to a host with this patch could silently change the ABI exposed to the guest, warranting that we default to the old behavior and opt-in for the new one. Reviewed-by: Jim Mattson Reviewed-by: Peter Shier Signed-off-by: Oliver Upton Change-Id: I202a0926f65035b872bfe8ad15307c026de59a98 Message-Id: <20200818152429.1923996-4-oupton@google.com> Reviewed-by: Wanpeng Li Signed-off-by: Paolo Bonzini --- include/uapi/linux/kvm.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include') diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index 58f43aa1fc21..ca41220b40b8 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -1052,6 +1052,7 @@ struct kvm_ppc_resize_hpt { #define KVM_CAP_STEAL_TIME 187 #define KVM_CAP_X86_USER_SPACE_MSR 188 #define KVM_CAP_X86_MSR_FILTER 189 +#define KVM_CAP_ENFORCE_PV_FEATURE_CPUID 190 #ifdef KVM_CAP_IRQ_ROUTING -- cgit v1.2.3