On 01/27/2011 10:33 AM, Nadav Har'El wrote:
In this patch we add a list of L0 (hardware) VMCSs, which we'll use to hold a
hardware VMCS for each active vmcs12 (i.e., for each L2 guest).
We call each of these L0 VMCSs a "vmcs02", as it is the VMCS that L0 uses
to run its nested guest L2.
+/*
+ * Allocate an L0 VMCS (vmcs02) for the current L1 VMCS (vmcs12), if one
+ * does not already exist. The allocation is done in L0 memory, so to avoid
+ * denial-of-service attack by guests, we limit the number of concurrently-
+ * allocated vmcss. A well-behaving L1 will VMCLEAR unused vmcs12s and not
+ * trigger this limit.
No, it won't. If you run N guests on a single-cpu kvm host, you'll have
N active VMCSs.
+ */
+static int nested_create_current_vmcs(struct kvm_vcpu *vcpu)
+{
+ struct vmcs_list *new_l2_guest;
+ struct vmcs *vmcs02;
+ struct vcpu_vmx *vmx = to_vmx(vcpu);
+
+ if (nested_get_current_vmcs(vmx))
+ return 0; /* nothing to do - we already have a VMCS */
+
+ if (vmx->nested.vmcs02_num>= NESTED_MAX_VMCS)
+ return -ENOMEM;
I asked to replace this by dropping the entire vmcs02_list (or perhaps
just its tail).
+static void __nested_free_saved_vmcs(void *arg)
+{
+ struct saved_vmcs *saved_vmcs = arg;
+ int cpu = raw_smp_processor_id();
+
+ if (saved_vmcs->cpu == cpu) /* TODO: how can this not be the case? */
+ vmcs_clear(saved_vmcs->vmcs);
This check will always be true.
+ if (per_cpu(current_vmcs, cpu) == saved_vmcs->vmcs)
+ per_cpu(current_vmcs, cpu) = NULL;
And this will always be false, no? Unless you free a vmcs02 while you
use it? Don't you always switch back to vmcs01 prior to freeing?
+}
+
skip_emulated_instruction(vcpu);
@@ -4050,6 +4190,8 @@ static void free_nested(struct vcpu_vmx
nested_release_page(vmx->nested.current_vmcs12_page);
vmx->nested.current_vmptr = -1ull;
}
+
+ nested_free_all_vmcs(vmx);
}
Maybe this is the counterexample - we kill a vcpu while it is in nested
mode.
--
error compiling committee.c: too many arguments to function
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