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Re: [Xen-devel] [PATCH v4 08/11] xen/arm: Handle remove foreign mapping
On 12/16/2013 04:33 PM, Ian Campbell wrote:
On Mon, 2013-12-16 at 16:26 +0000, Julien Grall wrote:
I have reworked this patch. I get a simpler patch:
commit aab2e5d2ae7d0fa87c74cae2f22044f87be33f70
Author: Julien Grall <julien.grall@xxxxxxxxxx>
Date: Fri Dec 13 16:51:03 2013 +0000
xen/arm: Handle remove foreign mapping
Modify get_page_from_gfn to take reference on foreign mapping. This will
avoid
specific handling in the common code.
Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
---
Changes in v5:
- Remove specific p2m handling in common code
- Handle foreign mapping in get_page_from_gfn
Changes in v4:
- Split patch #6 from dom0 pvh series v6.2 to retrieve only common
code.
- Rework commit title
- Rename xen_rem_foreign_from_p2m in p2m_remove_foreign
- Get the mfn from the pte. We are not sure that maddr given in
parameters is valid
Changes in v3:
- Move put_page in create_p2m_entries
- Move xenmem_rem_foreign_from_p2m in arch/arm/p2m.c
Changes in v2:
- Introduce the patch
diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index 39d8a03..f7bd7e2 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -317,10 +317,21 @@ static int create_p2m_entries(struct domain *d,
break;
case REMOVE:
{
- lpae_t pte;
+ lpae_t pte = third[third_table_offset(addr)];
+ unsigned long mfn;
+
+ maddr = (pte.bits & PADDR_MASK & PAGE_MASK);
I thought we had a macro for this, but apparently not. While looking for
it I spotted that x86 has pte_to_mfn, which sounds like a useful
innovation... (not essential as part of this series though).
+ mfn = paddr_to_pfn(maddr);
+
+ /* TODO: Handle other p2m type */
+ if ( pte.p2m.valid && p2m_is_foreign(pte.p2m.type) )
+ {
+ ASSERT(mfn_valid(mfn));
Something somewhere is making sure we don't put foreign MMIO regions
into the p2m, right?
I misread this part. And the answer is still yes because in this case
MMIO won't belong to a domain (there is no reference on it), so get_page
will return NULL when the foreign mapping is created in
xenmem_add_to_physmap_one.
+ put_page(mfn_to_page(mfn));
+ }
+
memset(&pte, 0x00, sizeof(pte));
write_pte(&third[third_table_offset(addr)], pte);
- maddr += PAGE_SIZE;
}
break;
}
diff --git a/xen/include/asm-arm/p2m.h b/xen/include/asm-arm/p2m.h
index 0eb07a8..e0b58da 100644
--- a/xen/include/asm-arm/p2m.h
+++ b/xen/include/asm-arm/p2m.h
@@ -122,9 +122,21 @@ static inline struct page_info *get_page_from_gfn(
if ( !mfn_valid(mfn) )
return NULL;
page = mfn_to_page(mfn);
- if ( !get_page(page, d) )
- return NULL;
- return page;
+
+ if ( get_page(page, d) )
This isn't noisy (even at debug level) on failure, I thought so?
Might be safer (and TBH more logical) to move it after the foreign
special case.
+ return page;
+
+ /* get_page won't work on foreign mapping because the page doesn't
+ * belong to the current domain.
+ */
+ if ( p2mt == p2m_map_foreign )
+ {
+ struct domain *fdom = page_get_owner_and_reference(page);
+ ASSERT(fdom != NULL);
ASSERT(fdom != d)
?
+ return page;
+ }
+
+ return NULL;
}
int get_page_type(struct page_info *page, unsigned long type);
--
Julien Grall
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