From b26f68c36bf6edaaa224f8a6ab285394af4d0f8c Mon Sep 17 00:00:00 2001 From: Vitaly Kuznetsov Date: Tue, 8 Jun 2021 14:08:15 +0200 Subject: [PATCH] i386: HV_HYPERCALL_AVAILABLE privilege bit is always needed According to TLFS, Hyper-V guest is supposed to check HV_HYPERCALL_AVAILABLE privilege bit before accessing HV_X64_MSR_GUEST_OS_ID/HV_X64_MSR_HYPERCALL MSRs but at least some Windows versions ignore that. As KVM is very permissive and allows accessing these MSRs unconditionally, no issue is observed. We may, however, want to tighten the checks eventually. Conforming to the spec is probably also a good idea. Enable HV_HYPERCALL_AVAILABLE bit unconditionally. Reviewed-by: Eduardo Habkost Signed-off-by: Vitaly Kuznetsov Message-Id: <20210608120817.1325125-8-vkuznets@redhat.com> Signed-off-by: Eduardo Habkost --- target/i386/kvm/kvm.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c index 945d24300c..eee1a6b46e 100644 --- a/target/i386/kvm/kvm.c +++ b/target/i386/kvm/kvm.c @@ -813,8 +813,6 @@ static struct { [HYPERV_FEAT_RELAXED] = { .desc = "relaxed timing (hv-relaxed)", .flags = { - {.func = HV_CPUID_FEATURES, .reg = R_EAX, - .bits = HV_HYPERCALL_AVAILABLE}, {.func = HV_CPUID_ENLIGHTMENT_INFO, .reg = R_EAX, .bits = HV_RELAXED_TIMING_RECOMMENDED} } @@ -823,7 +821,7 @@ static struct { .desc = "virtual APIC (hv-vapic)", .flags = { {.func = HV_CPUID_FEATURES, .reg = R_EAX, - .bits = HV_HYPERCALL_AVAILABLE | HV_APIC_ACCESS_AVAILABLE}, + .bits = HV_APIC_ACCESS_AVAILABLE}, {.func = HV_CPUID_ENLIGHTMENT_INFO, .reg = R_EAX, .bits = HV_APIC_ACCESS_RECOMMENDED} } @@ -832,8 +830,7 @@ static struct { .desc = "clocksources (hv-time)", .flags = { {.func = HV_CPUID_FEATURES, .reg = R_EAX, - .bits = HV_HYPERCALL_AVAILABLE | HV_TIME_REF_COUNT_AVAILABLE | - HV_REFERENCE_TSC_AVAILABLE} + .bits = HV_TIME_REF_COUNT_AVAILABLE | HV_REFERENCE_TSC_AVAILABLE} } }, [HYPERV_FEAT_CRASH] = { @@ -1346,6 +1343,9 @@ static int hyperv_fill_cpuids(CPUState *cs, c->ebx = hv_build_cpuid_leaf(cs, HV_CPUID_FEATURES, R_EBX); c->edx = hv_build_cpuid_leaf(cs, HV_CPUID_FEATURES, R_EDX); + /* Unconditionally required with any Hyper-V enlightenment */ + c->eax |= HV_HYPERCALL_AVAILABLE; + /* Not exposed by KVM but needed to make CPU hotplug in Windows work */ c->edx |= HV_CPU_DYNAMIC_PARTITIONING_AVAILABLE;