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i386: Hyper-V SynIC requires POST_MESSAGES/SIGNAL_EVENTS privileges 

When Hyper-V SynIC is enabled, we may need to allow Windows guests to make
hypercalls (POST_MESSAGES/SIGNAL_EVENTS). No issue is currently observed
because KVM is very permissive, allowing these hypercalls regarding of
guest visible CPUid bits.

Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20210608120817.1325125-9-vkuznets@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
This commit is contained in:
Vitaly Kuznetsov 2021-06-08 14:08:16 +02:00 committed by Eduardo Habkost
parent b26f68c36b
commit cce087f628
2 changed files with 12 additions and 0 deletions
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6
target/i386/kvm/hyperv-proto.h
View File

@ -38,6 +38,12 @@
#define HV_ACCESS_FREQUENCY_MSRS (1u << 11)
#define HV_ACCESS_REENLIGHTENMENTS_CONTROL (1u << 13)
/*
* HV_CPUID_FEATURES.EBX bits
*/
#define HV_POST_MESSAGES (1u << 4)
#define HV_SIGNAL_EVENTS (1u << 5)
/*
* HV_CPUID_FEATURES.EDX bits
*/

6
target/i386/kvm/kvm.c
View File

@ -1346,6 +1346,12 @@ static int hyperv_fill_cpuids(CPUState *cs,
/* Unconditionally required with any Hyper-V enlightenment */
c->eax |= HV_HYPERCALL_AVAILABLE;
/* SynIC and Vmbus devices require messages/signals hypercalls */
if (hyperv_feat_enabled(cpu, HYPERV_FEAT_SYNIC) &&
!cpu->hyperv_synic_kvm_only) {
c->ebx |= HV_POST_MESSAGES | HV_SIGNAL_EVENTS;
}
/* Not exposed by KVM but needed to make CPU hotplug in Windows work */
c->edx |= HV_CPU_DYNAMIC_PARTITIONING_AVAILABLE;