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Re: [Xen-devel] [V5 PATCH 6/7] pvh dom0: Add and remove foreign pages
On 12/05/2013 02:05 AM, Mukesh Rathor wrote:
In this patch, a new function, xenmem_add_foreign_to_p2m(), is added
to map pages from foreign guest into current dom0 for domU creation.
Such pages are typed p2m_map_foreign. Also, support is added here to
XENMEM_remove_from_physmap to remove such pages. Note, in the remove
path, we must release the refcount that was taken during the map phase.
Signed-off-by: Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>
---
xen/arch/x86/mm.c | 88 +++++++++++++++++++++++++++++++++++++++++----
xen/common/memory.c | 40 ++++++++++++++++++--
xen/include/asm-arm/p2m.h | 2 +
3 files changed, 119 insertions(+), 11 deletions(-)
diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index e3da479..1a4d564 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -2810,7 +2810,7 @@ static struct domain *get_pg_owner(domid_t domid)
goto out;
}
- if ( unlikely(paging_mode_translate(curr)) )
+ if ( !is_pvh_domain(curr) && unlikely(paging_mode_translate(curr)) )
{
MEM_LOG("Cannot mix foreign mappings with translated domains");
goto out;
@@ -4520,9 +4520,75 @@ static int handle_iomem_range(unsigned long s, unsigned
long e, void *p)
return 0;
}
+/*
+ * Add frames from foreign domain to target domain's physmap. Similar to
+ * XENMAPSPACE_gmfn but the frame is foreign being mapped into current,
+ * and is not removed from foreign domain.
+ * Usage: libxl on pvh dom0 creating a guest and doing privcmd_ioctl_mmap.
+ * Side Effect: the mfn for fgfn will be refcounted so it is not lost
+ * while mapped here. The refcnt is released in do_memory_op()
+ * via XENMEM_remove_from_physmap.
+ * Returns: 0 ==> success
+ */
+static int xenmem_add_foreign_to_p2m(struct domain *tdom, unsigned long fgfn,
+ unsigned long gpfn, struct domain *fdom)
+{
+ p2m_type_t p2mt, p2mt_prev;
+ int rc = 0;
+ unsigned long prev_mfn, mfn = 0;
+ struct page_info *page = NULL;
+
+ if ( tdom == fdom || !tdom || !fdom || !is_pvh_domain(tdom) )
+ return -EINVAL;
+
+ /* following will take a refcnt on the mfn */
+ page = get_page_from_gfn(fdom, fgfn, &p2mt, P2M_ALLOC);
+ if ( !page || !p2m_is_valid(p2mt) )
+ {
+ if ( page )
+ put_page(page);
+ return -EINVAL;
+ }
+ mfn = page_to_mfn(page);
+
+ /* Remove previously mapped page if it is present. */
+ prev_mfn = mfn_x(get_gfn(tdom, gpfn, &p2mt_prev));
+ if ( mfn_valid(prev_mfn) )
+ {
+ if ( is_xen_heap_mfn(prev_mfn) )
+ /* Xen heap frames are simply unhooked from this phys slot */
+ guest_physmap_remove_page(tdom, gpfn, prev_mfn, 0);
+ else
+ /* Normal domain memory is freed, to avoid leaking memory. */
+ guest_remove_page(tdom, gpfn);
+ }
+ /*
+ * Create the new mapping. Can't use guest_physmap_add_page() because it
+ * will update the m2p table which will result in mfn -> gpfn of dom0
+ * and not fgfn of domU.
+ */
+ if ( set_foreign_p2m_entry(tdom, gpfn, _mfn(mfn)) == 0 )
+ {
+ gdprintk(XENLOG_WARNING, "set_foreign_p2m_entry failed. "
+ "gpfn:%lx mfn:%lx fgfn:%lx td:%d fd:%d\n",
+ gpfn, mfn, fgfn, tdom->domain_id, fdom->domain_id);
+ put_page(page);
+ rc = -EINVAL;
+ }
+
+ /*
+ * We must do this put_gfn after set_foreign_p2m_entry so another cpu
+ * doesn't populate the gpfn before us.
+ */
+ put_gfn(tdom, gpfn);
+
+ return rc;
+}
+
static int xenmem_add_to_physmap_once(
struct domain *d,
- const struct xen_add_to_physmap *xatp)
+ const struct xen_add_to_physmap *xatp,
+ struct domain *fdom)
{
struct page_info *page = NULL;
unsigned long gfn = 0; /* gcc ... */
@@ -4581,6 +4647,13 @@ static int xenmem_add_to_physmap_once(
page = mfn_to_page(mfn);
break;
}
+
+ case XENMAPSPACE_gmfn_foreign:
+ {
+ rc = xenmem_add_foreign_to_p2m(d, xatp->idx, xatp->gpfn, fdom);
+ return rc;
+ }
+
default:
break;
}
@@ -4646,7 +4719,7 @@ static int xenmem_add_to_physmap(struct domain *d,
start_xatp = *xatp;
while ( xatp->size > 0 )
{
- rc = xenmem_add_to_physmap_once(d, xatp);
+ rc = xenmem_add_to_physmap_once(d, xatp, NULL);
if ( rc < 0 )
return rc;
@@ -4672,11 +4745,12 @@ static int xenmem_add_to_physmap(struct domain *d,
return rc;
}
- return xenmem_add_to_physmap_once(d, xatp);
+ return xenmem_add_to_physmap_once(d, xatp, NULL);
}
static int xenmem_add_to_physmap_range(struct domain *d,
- struct xen_add_to_physmap_range *xatpr)
+ struct xen_add_to_physmap_range *xatpr,
+ struct domain *fdom)
{
/* Process entries in reverse order to allow continuations */
while ( xatpr->size > 0 )
@@ -4693,7 +4767,7 @@ static int xenmem_add_to_physmap_range(struct domain *d,
xatp.space = xatpr->space;
xatp.idx = idx;
xatp.gpfn = gpfn;
- rc = xenmem_add_to_physmap_once(d, &xatp);
+ rc = xenmem_add_to_physmap_once(d, &xatp, fdom);
if ( copy_to_guest_offset(xatpr->errs, xatpr->size-1, &rc, 1) )
return -EFAULT;
@@ -4780,7 +4854,7 @@ long arch_memory_op(int op, XEN_GUEST_HANDLE_PARAM(void)
arg)
}
rc = xsm_add_to_physmap(XSM_TARGET, current->domain, d, fd);
if ( rc == 0 )
- rc = xenmem_add_to_physmap_range(d, &xatpr);
+ rc = xenmem_add_to_physmap_range(d, &xatpr, fd);
rcu_unlock_domain(d);
if ( fd )
diff --git a/xen/common/memory.c b/xen/common/memory.c
index eb7b72b..ae11828 100644
--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -675,9 +675,11 @@ long do_memory_op(unsigned long cmd,
XEN_GUEST_HANDLE_PARAM(void) arg)
case XENMEM_remove_from_physmap:
{
+ unsigned long mfn;
struct xen_remove_from_physmap xrfp;
struct page_info *page;
struct domain *d;
+ p2m_type_t p2mt;
if ( copy_from_guest(&xrfp, arg, 1) )
return -EFAULT;
@@ -693,11 +695,41 @@ long do_memory_op(unsigned long cmd,
XEN_GUEST_HANDLE_PARAM(void) arg)
return rc;
}
- page = get_page_from_gfn(d, xrfp.gpfn, NULL, P2M_ALLOC);
- if ( page )
+ /*
+ * if PVH, the gfn could be mapped to a mfn from foreign domain by the
+ * user space tool during domain creation. We need to check for that,
+ * free it up from the p2m, and release refcnt on it. In such a case,
+ * page would be NULL and the following call would not have refcnt'd
+ * the page. See also xenmem_add_foreign_to_p2m().
+ */
+ page = get_page_from_gfn(d, xrfp.gpfn, &p2mt, P2M_ALLOC);
+
+ if ( page || p2m_is_foreign(p2mt) )
{
- guest_physmap_remove_page(d, xrfp.gpfn, page_to_mfn(page), 0);
- put_page(page);
+ if ( page )
+ mfn = page_to_mfn(page);
+#ifdef CONFIG_X86
+ else
+ {
+ p2m_type_t tp;
+ struct domain *foreign_dom;
+
+ mfn = mfn_x(get_gfn_query(d, xrfp.gpfn, &tp));
+ foreign_dom = page_get_owner(mfn_to_page(mfn));
+ ASSERT(is_pvh_domain(d));
+ ASSERT(d != foreign_dom);
+ ASSERT(p2m_is_foreign(tp));
+ }
+#endif
Here, you can reduce the CONFIG_X86 something like that
else
{
stuct domain *foreign_dom;
#ifdef CONFIG_x86
p2m_type_t tp;
mfn = mfn_x(get_gfn_query(d, xrfp.gpfn, &tp);
ASSERT(is_pvh_domain(d));
ASSERT(p2m_is_forein(tp));
#else
mfn = gmfn_to_mfn(d, xrfp.gpfn);
#endif
foreign_dom = page_get_owner(mfn_to_page(mfn));
ASSERT(d != foreign_dom);
}
Until p2m_is_foreign(_t) is correctly setup on ARM, remove_from_physmap
in ARM will never go to the else part, so it's fine.
+ guest_physmap_remove_page(d, xrfp.gpfn, mfn, 0);
+ if (page)
+ put_page(page);
+
+ if ( p2m_is_foreign(p2mt) )
+ {
+ put_page(mfn_to_page(mfn));
+ put_gfn(d, xrfp.gpfn);
+ }
}
else
rc = -ENOENT;
diff --git a/xen/include/asm-arm/p2m.h b/xen/include/asm-arm/p2m.h
index c660820..f079f00 100644
--- a/xen/include/asm-arm/p2m.h
+++ b/xen/include/asm-arm/p2m.h
@@ -110,6 +110,8 @@ static inline int get_page_and_type(struct page_info *page,
return rc;
}
+#define p2m_is_foreign(_t) (0)
+
#endif /* _XEN_P2M_H */
/*
--
Julien Grall
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