On Mon, May 16, 2022 at 3:17 PM Peter Xu <peterx@xxxxxxxxxx> wrote:
>
> On Fri, Apr 29, 2022 at 06:39:35PM +0000, David Matlack wrote:
> > +static void perf_test_l1_guest_code(struct vmx_pages *vmx, uint64_t vcpu_id)
> > +{
> > +#define L2_GUEST_STACK_SIZE 64
> > + unsigned long l2_guest_stack[L2_GUEST_STACK_SIZE];
> > + unsigned long *rsp;
> > +
> > + GUEST_ASSERT(vmx->vmcs_gpa);
> > + GUEST_ASSERT(prepare_for_vmx_operation(vmx));
> > + GUEST_ASSERT(load_vmcs(vmx));
> > + GUEST_ASSERT(ept_1g_pages_supported());
> > +
> > + rsp = &l2_guest_stack[L2_GUEST_STACK_SIZE - 1];
> > + *rsp = vcpu_id;
> > + prepare_vmcs(vmx, perf_test_l2_guest_entry, rsp);
>
> Just to purely ask: is this setting the same stack pointer to all the
> vcpus?
No, but I understand the confusion since typically selftests use
symbols like "l2_guest_code" that are global. But "l2_guest_stack" is
actually a local variable so it will be allocated on the stack. Each
vCPU runs on a separate stack, so they will each run with their own
"l2_guest_stack".
>
> > +
> > + GUEST_ASSERT(!vmlaunch());
> > + GUEST_ASSERT(vmreadz(VM_EXIT_REASON) == EXIT_REASON_VMCALL);
> > + GUEST_DONE();
> > +}
>
> [...]
>
> > +/* Identity map the entire guest physical address space with 1GiB Pages. */
> > +void nested_map_all_1g(struct vmx_pages *vmx, struct kvm_vm *vm)
> > +{
> > + __nested_map(vmx, vm, 0, 0, vm->max_gfn << vm->page_shift, PG_LEVEL_1G);
> > +}
>
> Could max_gfn be large? Could it consumes a bunch of pages even if mapping
> 1G only?
Since the selftests only support 4-level EPT, this will use at most
513 pages. If we add support for 5-level EPT we may need to revisit
this approach.
>
> Thanks,
>
> --
> Peter Xu
>
