Confusion in acpi_sleep_machdep().
iedowse at iedowse.com
Mon Jan 1 18:46:50 PST 2007
In message <200612312043.kBVKhi7t095666 at apollo.backplane.com>, Matthew Dillon w
> I'm trying to figure out how the acpi_sleep_machdep() code works and
> there are a couple of lines I just don't understand:
> pm = vmspace_pmap(p->p_vmspace);
> cr3 = rcr3();
> page = PHYS_TO_VM_PAGE(sc->acpi_wakephys);
> pmap_enter(pm, sc->acpi_wakephys, page,
> VM_PROT_READ | VM_PROT_WRITE | VM_PROT_EXECUTE, 1);
> First, why isn't it just using kernel_pmap ? What's all the load_cr3()
> stuff for ?
> Second, why is it entering the physical address sc->acpi_wakephys
> as the virtual address in the pmap ? Shouldn't it be using
> sc->acpi_wakeaddr there?
> Anybody know ?
I don't know the details, but acpi_sleep_machdep() sets up an
identity mapping in the current process's vmspace (hence using
virtual = physical). Lazy switching of address spaces means that
cr3 may not currently refer to the same vmspace, which would break
the identity mapping, so that's the reason for the load_cr3() calls.
See revision 1.22 for a bit more information.
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