[Xen-ia64-devel] PAGE_ED in translate_domain_pte

[Tristan Gingold <Tristan.Gingold@xxxxxxxx>]

Hi,

I have a few questions about this changeset.
See questions in XXXXXXXXXXXX sections.

# HG changeset patch
# User awilliam@xxxxxxxxxxx
# Node ID bbf325d767687745c6838ac43fe48692b6792e54
# Parent  bd264ded5becccb904ce64c771e3853cca6abeef
[IA64] translate_domain_pte must handle ED bit and ignre bit[63:53]

made translate_domain_pte() aware _PAGE_ED bits.
_PAGE_PPN_MASK doesn't mask ED bit.
ED bit must be handled explicitly.
This case can occur by vcpu_itc_d().

Signed-off-by: Isaku Yamahata <yamahata@xxxxxxxxxxxxx>

diff -r bd264ded5bec -r bbf325d76768 xen/arch/ia64/xen/process.c
--- a/xen/arch/ia64/xen/process.c       Fri Apr 21 09:11:46 2006 -0600
+++ b/xen/arch/ia64/xen/process.c       Fri Apr 21 09:20:13 2006 -0600
@@ -87,9 +87,12 @@ unsigned long translate_domain_pte(unsig
        struct domain *d = current->domain;
        unsigned long mask, pteval2, mpaddr;
 
+       pteval &= ((1UL << 53) - 1);// ignore [63:53] bits
+
        // FIXME address had better be pre-validated on insert
        mask = ~itir_mask(itir);
-       mpaddr = ((pteval & _PAGE_PPN_MASK) & ~mask) | (address & mask);
+       mpaddr = (((pteval & ~_PAGE_ED) & _PAGE_PPN_MASK) & ~mask) |
+                (address & mask);
XXXXXXXXXXXXXXXXXXXXX
(pteval &~_PAGE_ED) & _PAGE_PPN_MASK
is equivalent to: pteval & (_PAGE_PPN_MASK & ~_PAGE_ED)
However _PAGE_PPN_MASK & _PAGE_ED = 0, so it is equivalent to
pteval & _PAGE_PPN_MASK
Therefore this change is useless.
Correct ?
XXXXXXXXXXXXXXXXXXX
        if (d == dom0) {
                if (mpaddr < dom0_start || mpaddr >= dom0_start + dom0_size) {
                        /*
@@ -114,6 +117,7 @@ unsigned long translate_domain_pte(unsig
        }
        pteval2 = lookup_domain_mpa(d,mpaddr);
        pteval2 &= _PAGE_PPN_MASK; // ignore non-addr bits
+       pteval2 |= (pteval & _PAGE_ED);
        pteval2 |= _PAGE_PL_2; // force PL0->2 (PL3 is unaffected)
        pteval2 = (pteval & ~_PAGE_PPN_MASK) | pteval2;
XXXXXXXXXXXXXXXX
~_PAGE_PPN_MASK | _PAGE_ED = ~_PAGE_PPN_MASK
Therefore the added line (+   ) is useless.
Correct ?
XXXXXXXXXXXXXXXX

Tristan.

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