On 06/28/2010 06:36 AM, Sheng Yang wrote:
Some guest device driver may leverage the "Non-Snoop" I/O, and explicitly
WBINVD or CLFLUSH to a RAM space. Since migration may occur before WBINVD or
CLFLUSH, we need to maintain data consistency either by:
Don't we always force enable snooping? Or is that only for the
processor, and you're worried about devices?
1: flushing cache (wbinvd) when the guest is scheduled out if there is no
wbinvd exit, or
2: execute wbinvd on all dirty physical CPUs when guest wbinvd exits.
/* fields used by HYPER-V emulation */
u64 hv_vapic;
+
+ cpumask_t wbinvd_dirty_mask;
};
Need alloc_cpumask_var()/free_cpumask_var() for very large hosts.
+static void wbinvd_ipi(void *garbage)
+{
+ wbinvd();
+}
Like Jan mentioned, this is quite heavy. What about a clflush() loop
instead? That may take more time, but at least it's preemptible. Of
course, it isn't preemptible in an IPI.
+
void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
{
+ /* Address WBINVD may be executed by guest */
+ if (vcpu->kvm->arch.iommu_domain) {
+ if (kvm_x86_ops->has_wbinvd_exit())
+ cpu_set(cpu, vcpu->arch.wbinvd_dirty_mask);
+ else if (vcpu->cpu != -1)
+ smp_call_function_single(vcpu->cpu,
+ wbinvd_ipi, NULL, 1);
Is there any point to doing this if !has_wbinvd_exit()? The vcpu might
not have migrated in time, so the cache is flushed too late.
+ }
+
kvm_x86_ops->vcpu_load(vcpu, cpu);
if (unlikely(per_cpu(cpu_tsc_khz, cpu) == 0)) {
unsigned long khz = cpufreq_quick_get(cpu);
@@ -3650,6 +3664,21 @@ int emulate_invlpg(struct kvm_vcpu *vcpu, gva_t address)
return X86EMUL_CONTINUE;
}
+int kvm_emulate_wbinvd(struct kvm_vcpu *vcpu)
+{
+ if (!vcpu->kvm->arch.iommu_domain)
+ return X86EMUL_CONTINUE;
+
+ if (kvm_x86_ops->has_wbinvd_exit()) {
+ smp_call_function_many(&vcpu->arch.wbinvd_dirty_mask,
+ wbinvd_ipi, NULL, 1);
+ cpus_clear(vcpu->arch.wbinvd_dirty_mask);
Race - a migration may set a new bit in wbinvd_dirty_mask after the
s_c_f_m().
However, it's probably benign, since we won't be entering the guest in
that period.
+ } else
+ wbinvd();
+ return X86EMUL_CONTINUE;
+}
+EXPORT_SYMBOL_GPL(kvm_emulate_wbinvd);
+
int emulate_clts(struct kvm_vcpu *vcpu)
{
kvm_x86_ops->set_cr0(vcpu, kvm_read_cr0_bits(vcpu, ~X86_CR0_TS));
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
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