Re: [Xen-devel] [PATCH 11/38] arm: implement p2m lookup

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2012-06-07 at 10:03 +0100, Tim Deegan wrote:
> At 15:39 +0000 on 01 Jun (1338565180), Ian Campbell wrote:
> > +/*
> > + * Lookup the MFN corresponding to a domain's PFN.
> > + *
> > + * There are no processor functions to do a stage 2 only lookup therefore 
> > we
> > + * do a a software walk.
> > + */
> > +paddr_t p2m_lookup(struct domain *d, paddr_t paddr)
> > +{
> > +    struct p2m_domain *p2m = &d->arch.p2m;
> > +    lpae_t pte, *first = NULL, *second = NULL, *third = NULL;
> > +    paddr_t maddr = INVALID_PADDR;
> > +
> > +    spin_lock(&p2m->lock);
> > +
> > +    first = __map_domain_page(p2m->first_level);
> > +    if ( !first[first_table_offset(paddr)].p2m.valid )
> > +        goto done_err;
> > +    if ( !first[first_table_offset(paddr)].p2m.table )
> > +    {
> > +        pte = first[first_table_offset(paddr)];
> > +        goto done;
> > +    }
> 
> This would be neater as: 
>        pte = first[first_table_offset(paddr)];
>        if ( !pte.p2m.valid || !pte.p2m.table )
>            goto done;
> 
> and test for pte.valid at 'done'.

Yes, that looks nice, although you still need a bit of a quirk for the
third level table bit. Patch below.

> It would be nice to do the three levels in a loop as well, but the weird
> way the table bit behaves in third-level entries might make that more
> confusing than the straight-line version.

This also has the same issue as with *_table_offset as the other similar
functions discussed earlier.

8<-----------------------------------------------------------

>From 347855d863303720cbf5ceb0f1e067660108d3f1 Mon Sep 17 00:00:00 2001
From: Ian Campbell <ian.campbell@xxxxxxxxxx>
Date: Fri, 13 Apr 2012 16:24:58 +0100
Subject: [PATCH] arm: implement p2m lookup

Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
---
 xen/arch/arm/p2m.c        |   45 +++++++++++++++++++++++++++++++++++++++++++++
 xen/include/asm-arm/p2m.h |    3 +++
 2 files changed, 48 insertions(+), 0 deletions(-)

diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index 6df5b62..145d9fe 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -32,6 +32,51 @@ void p2m_load_VTTBR(struct domain *d)
     isb(); /* Ensure update is visible */
 }
 
+/*
+ * Lookup the MFN corresponding to a domain's PFN.
+ *
+ * There are no processor functions to do a stage 2 only lookup therefore we
+ * do a a software walk.
+ */
+paddr_t p2m_lookup(struct domain *d, paddr_t paddr)
+{
+    struct p2m_domain *p2m = &d->arch.p2m;
+    lpae_t pte, *first = NULL, *second = NULL, *third = NULL;
+    paddr_t maddr = INVALID_PADDR;
+
+    spin_lock(&p2m->lock);
+
+    first = __map_domain_page(p2m->first_level);
+
+    pte = first[first_table_offset(paddr)];
+    if ( !pte.p2m.valid || !pte.p2m.table )
+        goto done;
+
+    second = map_domain_page(first[first_table_offset(paddr)].p2m.base);
+    pte = second[second_table_offset(paddr)];
+    if ( !pte.p2m.valid || !pte.p2m.table )
+        goto done;
+
+    third = map_domain_page(second[second_table_offset(paddr)].p2m.base);
+    pte = third[third_table_offset(paddr)];
+
+    /* This bit must be one in the level 3 entry */
+    if ( !pte.p2m.table )
+        pte.bits = 0;
+
+done:
+    if ( pte.p2m.valid )
+        maddr = (pte.bits & PADDR_MASK & PAGE_MASK) | (paddr & ~PAGE_MASK);
+
+    if (third) unmap_domain_page(third);
+    if (second) unmap_domain_page(second);
+    if (first) unmap_domain_page(first);
+
+    spin_unlock(&p2m->lock);
+
+    return maddr;
+}
+
 int guest_physmap_mark_populate_on_demand(struct domain *d,
                                           unsigned long gfn,
                                           unsigned int order)
diff --git a/xen/include/asm-arm/p2m.h b/xen/include/asm-arm/p2m.h
index 349923a..1afd5cb 100644
--- a/xen/include/asm-arm/p2m.h
+++ b/xen/include/asm-arm/p2m.h
@@ -32,6 +32,9 @@ int p2m_alloc_table(struct domain *d);
 /* */
 void p2m_load_VTTBR(struct domain *d);
 
+/* */
+paddr_t p2m_lookup(struct domain *d, paddr_t gpfn);
+
 /* Setup p2m RAM mapping for domain d from start-end. */
 int p2m_populate_ram(struct domain *d, paddr_t start, paddr_t end);
 /* Map MMIO regions in the p2m: start_gaddr and end_gaddr is the range
-- 
1.7.9.1





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