Matias Zabaljauregui wrote:
Jeremy, I fixed the code following your comments (hope you still
remember).
I'd like to ask you again about this one:
/* Found in switcher.S */
extern unsigned long default_idt_entries[];
diff --git a/arch/x86/include/asm/lguest_hcall.h
b/arch/x86/include/asm/lguest_hcall.h
index 0f4ee71..3860153 100644
--- a/arch/x86/include/asm/lguest_hcall.h
+++ b/arch/x86/include/asm/lguest_hcall.h
@@ -17,6 +17,7 @@
#define LHCALL_SET_PMD 15
#define LHCALL_LOAD_TLS 16
#define LHCALL_NOTIFY 17
+#define LHCALL_SET_PUD 18
PGD is more accurate than PUD (here, and the rest of the patch). The
pud level of the pagetable is the 4th level used by 64-bit; PAE just has
PGD, PMD and PTE levels. Due to pagetable level folding, the PGD is
sometimes referred to as the PUD when looking "up" the pagetable tree
(ie, the PUD is logically the next level up from the PMD), but its still
just an alias for the PGD. Since the hypervisor interface shouldn't
care about how the guest OS manages its pagetables, it should use a
consistent naming for the levels as they "really" are. Lguest
traditionally uses the same names that Linux does, so PGD is appropriate.
I understand, but then should we change also the LHCALL_SET_PMD name ?
this is the one used for setting a new pgd when PAE is NOT activated.
Yeah, that would be consistent. In non-PAE, the pmd is just the next
logical level up from the pte, but just an alias name for the pgd.
So, just to confirm: even if we are implementing pv_mmu_ops.set_pud
replacement (lguest_set_pud in our case), we should use LHCALL_SET_PGD
hypercall name in this code because that is what host is going to
actually do?
Yeah, I guess. The set_pud notation makes some sense within Linux
because of its pagetable-folding, but the actual lguest implementation
is mapping between the guest's abstractions to the hypervisor abi's.
(In Xen this wasn't much of an issue because its the same hypercall for
updating a pagetable at any level, and the hypervisor can work out
what's going on for itself.)
J
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