Olaf Hering
2011-Oct-19 14:23 UTC
[Xen-devel] [PATCH 0 of 3] xenpaging fixes for xen-unstable
The following changes for xenpaging add checking for the p2mt in the page-in path to make the functions more robust, add some documentation to each p2m_mem_paging function, and disable paging in a PoD guest. Please review and apply. Olaf tools/xenpaging/xenpaging.c | 3 + xen/arch/x86/mm/mem_event.c | 6 ++ xen/arch/x86/mm/p2m.c | 111 ++++++++++++++++++++++++++++++++++++++++++-- 3 files changed, 116 insertions(+), 4 deletions(-) _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Olaf Hering
2011-Oct-19 14:23 UTC
[Xen-devel] [PATCH 1 of 3] xenpaging: check p2mt in p2m_mem_paging functions
# HG changeset patch
# User Olaf Hering <olaf@aepfle.de>
# Date 1319034159 -7200
# Node ID f835012a0c062e70495aa341d41e3970a121bf6a
# Parent 6880bfc48504db31e2680de01bfadf4db3b0b7a0
xenpaging: check p2mt in p2m_mem_paging functions
Add checks to forward the p2m_ram_paging* state properly during page-in.
Resume can be called several times if several vcpus called populate for
the gfn. Finish resume only once.
v2:
- remove debug output for non-p2m_ram_rw case
Signed-off-by: Olaf Hering <olaf@aepfle.de>
diff -r 6880bfc48504 -r f835012a0c06 xen/arch/x86/mm/p2m.c
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -851,16 +851,22 @@ int p2m_mem_paging_prep(struct domain *d
p2m_access_t a;
mfn_t mfn;
struct p2m_domain *p2m = p2m_get_hostp2m(d);
- int ret = -ENOMEM;
+ int ret;
p2m_lock(p2m);
mfn = p2m->get_entry(p2m, gfn, &p2mt, &a, p2m_query, NULL);
+ ret = -ENOENT;
+ /* Allow only missing pages */
+ if ( p2mt != p2m_ram_paging_in_start )
+ goto out;
+
/* Allocate a page if the gfn does not have one yet */
if ( !mfn_valid(mfn) )
{
/* Get a free page */
+ ret = -ENOMEM;
page = alloc_domheap_page(p2m->domain, 0);
if ( unlikely(page == NULL) )
goto out;
@@ -896,9 +902,13 @@ void p2m_mem_paging_resume(struct domain
{
p2m_lock(p2m);
mfn = p2m->get_entry(p2m, rsp.gfn, &p2mt, &a, p2m_query,
NULL);
- set_p2m_entry(p2m, rsp.gfn, mfn, 0, p2m_ram_rw, a);
- set_gpfn_from_mfn(mfn_x(mfn), rsp.gfn);
- audit_p2m(p2m, 1);
+ /* Allow only pages which were prepared properly, or pages which were
nominated but not evicted */
+ if ( mfn_valid(mfn) && ( p2mt == p2m_ram_paging_in || p2mt ==
p2m_ram_paging_in_start ) )
+ {
+ set_p2m_entry(p2m, rsp.gfn, mfn, 0, p2m_ram_rw, a);
+ set_gpfn_from_mfn(mfn_x(mfn), rsp.gfn);
+ audit_p2m(p2m, 1);
+ }
p2m_unlock(p2m);
}
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Olaf Hering
2011-Oct-19 14:23 UTC
[Xen-devel] [PATCH 2 of 3] xenpaging: document p2m_mem_paging functions
# HG changeset patch
# User Olaf Hering <olaf@aepfle.de>
# Date 1319034159 -7200
# Node ID cc6184fcd784f94165417073935c5fd0c4b4a76e
# Parent f835012a0c062e70495aa341d41e3970a121bf6a
xenpaging: document p2m_mem_paging functions
Add some documentation for each of the p2m_mem_paging functions to describe
what they ought to do.
Signed-off-by: Olaf Hering <olaf@aepfle.de>
diff -r f835012a0c06 -r cc6184fcd784 xen/arch/x86/mm/p2m.c
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -668,6 +668,24 @@ set_shared_p2m_entry(struct domain *d, u
}
#ifdef __x86_64__
+/**
+ * p2m_mem_paging_nominate - Mark a guest page as to-be-paged-out
+ * @d: guest domain
+ * @gfn: guest page to nominate
+ *
+ * Returns 0 for success or negative errno values if gfn is not pageable.
+ *
+ * p2m_mem_paging_nominate() is called by the pager and checks if a guest page
+ * can be paged out. If the following conditions are met the p2mt will be
+ * changed:
+ * - the gfn is backed by a mfn
+ * - the p2mt of the gfn is pageable
+ * - the mfn is not used for IO
+ * - the mfn has exactly one user and has no special meaning
+ *
+ * Once the p2mt is changed the page is readonly for the guest. On success the
+ * pager can write the page contents to disk and later evict the page.
+ */
int p2m_mem_paging_nominate(struct domain *d, unsigned long gfn)
{
struct page_info *page;
@@ -714,6 +732,25 @@ int p2m_mem_paging_nominate(struct domai
return ret;
}
+/**
+ * p2m_mem_paging_evict - Mark a guest page as paged-out
+ * @d: guest domain
+ * @gfn: guest page to evict
+ *
+ * Returns 0 for success or negative errno values if eviction is not possible.
+ *
+ * p2m_mem_paging_evict() is called by the pager and will free a guest page and
+ * release it back to Xen. If the following conditions are met the page can be
+ * freed:
+ * - the gfn is backed by a mfn
+ * - the gfn was nominated
+ * - the mfn has still exactly one user and has no special meaning
+ *
+ * After successful nomination some other process could have mapped the page.
In
+ * this case eviction can not be done. If the gfn was populated before the
pager
+ * could evict it, eviction can not be done either. In this case the gfn is
+ * still backed by a mfn.
+ */
int p2m_mem_paging_evict(struct domain *d, unsigned long gfn)
{
struct page_info *page;
@@ -773,6 +810,15 @@ int p2m_mem_paging_evict(struct domain *
return ret;
}
+/**
+ * p2m_mem_paging_drop_page - Tell pager to drop its reference to a paged page
+ * @d: guest domain
+ * @gfn: guest page to drop
+ *
+ * p2m_mem_paging_drop_page() will notify the pager that a paged-out gfn was
+ * released by the guest. The pager is supposed to drop its reference of the
+ * gfn.
+ */
void p2m_mem_paging_drop_page(struct domain *d, unsigned long gfn)
{
struct vcpu *v = current;
@@ -791,6 +837,27 @@ void p2m_mem_paging_drop_page(struct dom
}
}
+/**
+ * p2m_mem_paging_populate - Tell pager to populete a paged page
+ * @d: guest domain
+ * @gfn: guest page in paging state
+ *
+ * p2m_mem_paging_populate() will notify the pager that a page in any of the
+ * paging states needs to be written back into the guest.
+ * This function needs to be called whenever gfn_to_mfn() returns any of the
p2m
+ * paging types because the gfn may not be backed by a mfn.
+ *
+ * The gfn can be in any of the paging states, but the pager needs only be
+ * notified when the gfn is in the paging-out path (paging_out or paged). This
+ * function may be called more than once from several vcpus. If the vcpu
belongs
+ * to the guest, the vcpu must be stopped and the pager notified that the vcpu
+ * was stopped. The pager needs to handle several requests for the same gfn.
+ *
+ * If the gfn is not in the paging-out path and the vcpu does not belong to the
+ * guest, nothing needs to be done and the function assumes that a request was
+ * already sent to the pager. In this case the caller has to try again until
the
+ * gfn is fully paged in again.
+ */
void p2m_mem_paging_populate(struct domain *d, unsigned long gfn)
{
struct vcpu *v = current;
@@ -844,6 +911,17 @@ void p2m_mem_paging_populate(struct doma
mem_event_put_request(d, &d->mem_paging, &req);
}
+/**
+ * p2m_mem_paging_prep - Allocate a new page for the guest
+ * @d: guest domain
+ * @gfn: guest page in paging state
+ *
+ * p2m_mem_paging_prep() will allocate a new page for the guest if the gfn is
+ * not backed by a mfn. It is called by the pager.
+ * It is required that the gfn was already populated. The gfn may already have
a
+ * mfn if populate was called for gfn which was nominated but not evicted. In
+ * this case only the p2mt needs to be forwarded.
+ */
int p2m_mem_paging_prep(struct domain *d, unsigned long gfn)
{
struct page_info *page;
@@ -886,6 +964,21 @@ int p2m_mem_paging_prep(struct domain *d
return ret;
}
+/**
+ * p2m_mem_paging_resume - Resume guest gfn and vcpus
+ * @d: guest domain
+ * @gfn: guest page in paging state
+ *
+ * p2m_mem_paging_resume() will forward the p2mt of a gfn to ram_rw and all
+ * waiting vcpus will be unpaused again. It is called by the pager.
+ *
+ * The gfn was previously either evicted and populated, or nominated and
+ * populated. If the page was evicted the p2mt will be p2m_ram_paging_in. If
+ * the page was just nominated the p2mt will be p2m_ram_paging_in_start because
+ * the pager did not call p2m_mem_paging_prep().
+ *
+ * If the gfn was dropped the vcpu needs to be unpaused.
+ */
void p2m_mem_paging_resume(struct domain *d)
{
struct p2m_domain *p2m = p2m_get_hostp2m(d);
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Olaf Hering
2011-Oct-19 14:23 UTC
[Xen-devel] [PATCH 3 of 3] xenpaging: disallow paging in a PoD guest
# HG changeset patch
# User Olaf Hering <olaf@aepfle.de>
# Date 1319034160 -7200
# Node ID d56219addb9e921a02bce5fa8a97c43eba9bc914
# Parent cc6184fcd784f94165417073935c5fd0c4b4a76e
xenpaging: disallow paging in a PoD guest
Disallow xenpaging in a PoD guest until coexistance between the two features
is properly implemented.
Signed-off-by: Olaf Hering <olaf@aepfle.de>
diff -r cc6184fcd784 -r d56219addb9e tools/xenpaging/xenpaging.c
--- a/tools/xenpaging/xenpaging.c
+++ b/tools/xenpaging/xenpaging.c
@@ -246,6 +246,9 @@ static xenpaging_t *xenpaging_init(domid
case ENODEV:
ERROR("EPT not supported for this guest");
break;
+ case EXDEV:
+ ERROR("xenpaging not supported in a PoD guest");
+ break;
default:
ERROR("Error initialising shared page: %s",
strerror(errno));
break;
diff -r cc6184fcd784 -r d56219addb9e xen/arch/x86/mm/mem_event.c
--- a/xen/arch/x86/mm/mem_event.c
+++ b/xen/arch/x86/mm/mem_event.c
@@ -253,6 +253,7 @@ int mem_event_domctl(struct domain *d, x
case XEN_DOMCTL_MEM_EVENT_OP_PAGING:
{
struct mem_event_domain *med = &d->mem_paging;
+ struct p2m_domain *p2m = p2m_get_hostp2m(d);
rc = -ENODEV;
/* Only HAP is supported */
if ( !hap_enabled(d) )
@@ -262,6 +263,11 @@ int mem_event_domctl(struct domain *d, x
if ( boot_cpu_data.x86_vendor != X86_VENDOR_INTEL )
break;
+ rc = -EXDEV;
+ /* Disallow paging in a PoD guest */
+ if ( p2m->pod.entry_count )
+ break;
+
switch( mec->op )
{
case XEN_DOMCTL_MEM_EVENT_OP_PAGING_ENABLE:
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Tim Deegan
2011-Oct-20 10:32 UTC
Re: [Xen-devel] [PATCH 0 of 3] xenpaging fixes for xen-unstable
At 16:23 +0200 on 19 Oct (1319041400), Olaf Hering wrote:> > The following changes for xenpaging add checking for the p2mt in the page-in > path to make the functions more robust, add some documentation to each > p2m_mem_paging function, and disable paging in a PoD guest. > > Please review and apply.Applied, thanks. Double thanks for adding documentation! Tim. _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel