From: Vitaly Kuznetsov Date: Fri, 21 May 2021 09:51:55 +0000 (+0200) Subject: KVM: x86: hyper-v: Check access to HVCALL_NOTIFY_LONG_SPIN_WAIT hypercall X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=34ef7d7b9c0422316ee2c34c564b222255c91532;p=linux.git KVM: x86: hyper-v: Check access to HVCALL_NOTIFY_LONG_SPIN_WAIT hypercall TLFS6.0b states that partition issuing HVCALL_NOTIFY_LONG_SPIN_WAIT must posess 'UseHypercallForLongSpinWait' privilege but there's no corresponding feature bit. Instead, we have "Recommended number of attempts to retry a spinlock failure before notifying the hypervisor about the failures. 0xFFFFFFFF indicates never notify." Use this to check access to the hypercall. Also, check against zero as the corresponding CPUID must be set (and '0' attempts before re-try is weird anyway). Signed-off-by: Vitaly Kuznetsov Signed-off-by: Paolo Bonzini Message-Id: <20210521095204.2161214-22-vkuznets@redhat.com> Signed-off-by: Paolo Bonzini --- diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c index 51fc74ea773f3..13bfa4e0b93db 100644 --- a/arch/x86/kvm/hyperv.c +++ b/arch/x86/kvm/hyperv.c @@ -2092,6 +2092,17 @@ static void kvm_hv_hypercall_read_xmm(struct kvm_hv_hcall *hc) static bool hv_check_hypercall_access(struct kvm_vcpu_hv *hv_vcpu, u16 code) { + if (!hv_vcpu->enforce_cpuid) + return true; + + switch (code) { + case HVCALL_NOTIFY_LONG_SPIN_WAIT: + return hv_vcpu->cpuid_cache.enlightenments_ebx && + hv_vcpu->cpuid_cache.enlightenments_ebx != U32_MAX; + default: + break; + } + return true; }