[PATCH v9] x86/mem-sharing: mem-sharing a range of memory

[PATCH v9] x86/mem-sharing: mem-sharing a range of memory

[Tamas K Lengyel]

Currently mem-sharing can be performed on a page-by-page basis from the control
domain. However, this process is quite wasteful when a range of pages have to
be deduplicated.

This patch introduces a new mem_sharing memop for range sharing where
the user doesn't have to separately nominate each page in both the source and
destination domain, and the looping over all pages happen in the hypervisor.
This significantly reduces the overhead of sharing a range of memory.

Signed-off-by: Tamas K Lengyel <tamas.lengyel@zentific.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: George Dunlap <george.dunlap@eu.citrix.com>
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>

v9: style fixes and minor adjustments
---
 tools/libxc/include/xenctrl.h        |  15 ++++
 tools/libxc/xc_memshr.c              |  19 +++++
 tools/tests/mem-sharing/memshrtool.c |  22 ++++++
 xen/arch/x86/mm/mem_sharing.c        | 142 +++++++++++++++++++++++++++++++++++
 xen/include/public/memory.h          |  10 ++-
 5 files changed, 207 insertions(+), 1 deletion(-)

diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
index fdc148a..560ce7b 100644
--- a/tools/libxc/include/xenctrl.h
+++ b/tools/libxc/include/xenctrl.h
@@ -2334,6 +2334,21 @@ int xc_memshr_add_to_physmap(xc_interface *xch,
                     domid_t client_domain,
                     unsigned long client_gfn);
 
+/* Allows to deduplicate a range of memory of a client domain. Using
+ * this function is equivalent of calling xc_memshr_nominate_gfn for each gfn
+ * in the two domains followed by xc_memshr_share_gfns.
+ *
+ * May fail with -EINVAL if the source and client domain have different
+ * memory size or if memory sharing is not enabled on either of the domains.
+ * May also fail with -ENOMEM if there isn't enough memory available to store
+ * the sharing metadata before deduplication can happen.
+ */
+int xc_memshr_range_share(xc_interface *xch,
+                          domid_t source_domain,
+                          domid_t client_domain,
+                          uint64_t first_gfn,
+                          uint64_t last_gfn);
+
 /* Debug calls: return the number of pages referencing the shared frame backing
  * the input argument. Should be one or greater. 
  *
diff --git a/tools/libxc/xc_memshr.c b/tools/libxc/xc_memshr.c
index deb0aa4..f53a59a 100644
--- a/tools/libxc/xc_memshr.c
+++ b/tools/libxc/xc_memshr.c
@@ -181,6 +181,25 @@ int xc_memshr_add_to_physmap(xc_interface *xch,
     return xc_memshr_memop(xch, source_domain, &mso);
 }
 
+int xc_memshr_range_share(xc_interface *xch,
+                          domid_t source_domain,
+                          domid_t client_domain,
+                          uint64_t first_gfn,
+                          uint64_t last_gfn)
+{
+    xen_mem_sharing_op_t mso;
+
+    memset(&mso, 0, sizeof(mso));
+
+    mso.op = XENMEM_sharing_op_range_share;
+
+    mso.u.range.client_domain = client_domain;
+    mso.u.range.first_gfn = first_gfn;
+    mso.u.range.last_gfn = last_gfn;
+
+    return xc_memshr_memop(xch, source_domain, &mso);
+}
+
 int xc_memshr_domain_resume(xc_interface *xch,
                             domid_t domid)
 {
diff --git a/tools/tests/mem-sharing/memshrtool.c b/tools/tests/mem-sharing/memshrtool.c
index 437c7c9..8e5e22b 100644
--- a/tools/tests/mem-sharing/memshrtool.c
+++ b/tools/tests/mem-sharing/memshrtool.c
@@ -24,6 +24,8 @@ static int usage(const char* prog)
     printf("  nominate <domid> <gfn>  - Nominate a page for sharing.\n");
     printf("  share <domid> <gfn> <handle> <source> <source-gfn> <source-handle>\n");
     printf("                          - Share two pages.\n");
+    printf("  range <source-domid> <destination-domid> <first-gfn> <last-gfn>\n");
+    printf("                          - Share pages between domains in a range.\n");
     printf("  unshare <domid> <gfn>   - Unshare a page by grabbing a writable map.\n");
     printf("  add-to-physmap <domid> <gfn> <source> <source-gfn> <source-handle>\n");
     printf("                          - Populate a page in a domain with a shared page.\n");
@@ -180,6 +182,26 @@ int main(int argc, const char** argv)
         }
         printf("Audit returned %d errors.\n", rc);
     }
+    else if( !strcasecmp(cmd, "range") )
+    {
+        domid_t sdomid, cdomid;
+        int rc;
+        uint64_t first_gfn, last_gfn;
+
+        if ( argc != 6 )
+            return usage(argv[0]);
 
+        sdomid = strtol(argv[2], NULL, 0);
+        cdomid = strtol(argv[3], NULL, 0);
+        first_gfn = strtoul(argv[4], NULL, 0);
+        last_gfn = strtoul(argv[5], NULL, 0);
+
+        rc = xc_memshr_range_share(xch, sdomid, cdomid, first_gfn, last_gfn);
+        if ( rc < 0 )
+        {
+            printf("error executing xc_memshr_range_share: %s\n", strerror(errno));
+            return rc;
+        }
+    }
     return 0;
 }
diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c
index 47e0820..eb7674f 100644
--- a/xen/arch/x86/mm/mem_sharing.c
+++ b/xen/arch/x86/mm/mem_sharing.c
@@ -1324,6 +1324,58 @@ int relinquish_shared_pages(struct domain *d)
     return rc;
 }
 
+static int range_share(struct domain *d, struct domain *cd,
+                       struct mem_sharing_op_range *range)
+{
+    int rc = 0;
+    shr_handle_t sh, ch;
+    unsigned long start = range->opaque ?: range->first_gfn;
+
+    while ( range->last_gfn >= start )
+    {
+        /*
+         * We only break out if we run out of memory as individual pages may
+         * legitimately be unsharable and we just want to skip over those.
+         */
+        rc = mem_sharing_nominate_page(d, start, 0, &sh);
+        if ( rc == -ENOMEM )
+            break;
+
+        if ( !rc )
+        {
+            rc = mem_sharing_nominate_page(cd, start, 0, &ch);
+            if ( rc == -ENOMEM )
+                break;
+
+            if ( !rc )
+            {
+                /* If we get here this should be guaranteed to succeed. */
+                rc = mem_sharing_share_pages(d, start, sh,
+                                             cd, start, ch);
+                ASSERT(!rc);
+            }
+        }
+
+        /* Check for continuation if it's not the last iteration. */
+        if ( range->last_gfn >= ++start && hypercall_preempt_check() )
+        {
+            rc = 1;
+            break;
+        }
+    }
+
+    range->opaque = start;
+
+    /*
+     * The last page may fail with -EINVAL, and for range sharing we don't
+     * care about that.
+     */
+    if ( range->last_gfn < start && rc == -EINVAL )
+        rc = 0;
+
+    return rc;
+}
+
 int mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg)
 {
     int rc;
@@ -1498,6 +1550,96 @@ int mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg)
         }
         break;
 
+        case XENMEM_sharing_op_range_share:
+        {
+            unsigned long max_sgfn, max_cgfn;
+            struct domain *cd;
+
+            rc = -EINVAL;
+            if ( mso.u.range._pad[0] || mso.u.range._pad[1] ||
+                 mso.u.range._pad[2] )
+                 goto out;
+
+            /*
+             * We use opaque for the hypercall continuation value.
+             * Ideally the user sets this to 0 in the beginning but
+             * there is no good way of enforcing that here, so we just check
+             * that it's at least in range.
+             */
+            if ( mso.u.range.opaque &&
+                 (mso.u.range.opaque < mso.u.range.first_gfn ||
+                  mso.u.range.opaque > mso.u.range.last_gfn) )
+                goto out;
+
+            if ( !mem_sharing_enabled(d) )
+                goto out;
+
+            rc = rcu_lock_live_remote_domain_by_id(mso.u.range.client_domain,
+                                                   &cd);
+            if ( rc )
+                goto out;
+
+            /*
+             * We reuse XENMEM_sharing_op_share XSM check here as this is
+             * essentially the same concept repeated over multiple pages.
+             */
+            rc = xsm_mem_sharing_op(XSM_DM_PRIV, d, cd,
+                                    XENMEM_sharing_op_share);
+            if ( rc )
+            {
+                rcu_unlock_domain(cd);
+                goto out;
+            }
+
+            if ( !mem_sharing_enabled(cd) )
+            {
+                rcu_unlock_domain(cd);
+                rc = -EINVAL;
+                goto out;
+            }
+
+            /*
+             * Sanity check only, the client should keep the domains paused for
+             * the duration of this op.
+             */
+            if ( !atomic_read(&d->pause_count) ||
+                 !atomic_read(&cd->pause_count) )
+            {
+                rcu_unlock_domain(cd);
+                rc = -EINVAL;
+                goto out;
+            }
+
+            max_sgfn = domain_get_maximum_gpfn(d);
+            max_cgfn = domain_get_maximum_gpfn(cd);
+
+            if ( max_sgfn < mso.u.range.first_gfn ||
+                 max_sgfn < mso.u.range.last_gfn ||
+                 max_cgfn < mso.u.range.first_gfn ||
+                 max_cgfn < mso.u.range.last_gfn )
+            {
+                rcu_unlock_domain(cd);
+                rc = -EINVAL;
+                goto out;
+            }
+
+            rc = range_share(d, cd, &mso.u.range);
+            rcu_unlock_domain(cd);
+
+            if ( rc > 0 )
+            {
+                if ( __copy_to_guest(arg, &mso, 1) )
+                    rc = -EFAULT;
+                else
+                    rc = hypercall_create_continuation(__HYPERVISOR_memory_op,
+                                                       "lh", XENMEM_sharing_op,
+                                                       arg);
+            }
+            else
+                mso.u.range.opaque = 0;
+        }
+        break;
+
         case XENMEM_sharing_op_debug_gfn:
         {
             unsigned long gfn = mso.u.debug.u.gfn;
diff --git a/xen/include/public/memory.h b/xen/include/public/memory.h
index 29ec571..3badfb9 100644
--- a/xen/include/public/memory.h
+++ b/xen/include/public/memory.h
@@ -465,6 +465,7 @@ DEFINE_XEN_GUEST_HANDLE(xen_mem_access_op_t);
 #define XENMEM_sharing_op_debug_gref        5
 #define XENMEM_sharing_op_add_physmap       6
 #define XENMEM_sharing_op_audit             7
+#define XENMEM_sharing_op_range_share       8
 
 #define XENMEM_SHARING_OP_S_HANDLE_INVALID  (-10)
 #define XENMEM_SHARING_OP_C_HANDLE_INVALID  (-9)
@@ -500,7 +501,14 @@ struct xen_mem_sharing_op {
             uint64_aligned_t client_gfn;    /* IN: the client gfn */
             uint64_aligned_t client_handle; /* IN: handle to the client page */
             domid_t  client_domain; /* IN: the client domain id */
-        } share; 
+        } share;
+        struct mem_sharing_op_range {         /* OP_RANGE_SHARE */
+            uint64_aligned_t first_gfn;      /* IN: the first gfn */
+            uint64_aligned_t last_gfn;       /* IN: the last gfn */
+            uint64_aligned_t opaque;         /* Must be set to 0 */
+            domid_t client_domain;           /* IN: the client domain id */
+            uint16_t _pad[3];                /* Must be set to 0 */
+        } range;
         struct mem_sharing_op_debug {     /* OP_DEBUG_xxx */
             union {
                 uint64_aligned_t gfn;      /* IN: gfn to debug          */
-- 
2.8.1


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Re: [PATCH v9] x86/mem-sharing: mem-sharing a range of memory

[Wei Liu]

On Mon, Aug 01, 2016 at 11:14:27AM -0600, Tamas K Lengyel wrote:
> Currently mem-sharing can be performed on a page-by-page basis from the control
> domain. However, this process is quite wasteful when a range of pages have to
> be deduplicated.
> 
> This patch introduces a new mem_sharing memop for range sharing where
> the user doesn't have to separately nominate each page in both the source and
> destination domain, and the looping over all pages happen in the hypervisor.
> This significantly reduces the overhead of sharing a range of memory.
> 
> Signed-off-by: Tamas K Lengyel <tamas.lengyel@zentific.com>
> Acked-by: Wei Liu <wei.liu2@citrix.com>
> Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

I notice this patch has got sufficient acks.

I will queue this up.

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Re: [PATCH v9] x86/mem-sharing: mem-sharing a range of memory

[Tamas K Lengyel]

[-- Attachment #1.1: Type: text/plain, Size: 893 bytes --]

On Aug 2, 2016 06:17, "Wei Liu" <wei.liu2@citrix.com> wrote:
>
> On Mon, Aug 01, 2016 at 11:14:27AM -0600, Tamas K Lengyel wrote:
> > Currently mem-sharing can be performed on a page-by-page basis from the
control
> > domain. However, this process is quite wasteful when a range of pages
have to
> > be deduplicated.
> >
> > This patch introduces a new mem_sharing memop for range sharing where
> > the user doesn't have to separately nominate each page in both the
source and
> > destination domain, and the looping over all pages happen in the
hypervisor.
> > This significantly reduces the overhead of sharing a range of memory.
> >
> > Signed-off-by: Tamas K Lengyel <tamas.lengyel@zentific.com>
> > Acked-by: Wei Liu <wei.liu2@citrix.com>
> > Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
>
> I notice this patch has got sufficient acks.
>
> I will queue this up.

Thanks!
Tamas

[-- Attachment #1.2: Type: text/html, Size: 1325 bytes --]

[-- Attachment #2: Type: text/plain, Size: 127 bytes --]

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Re: [PATCH v9] x86/mem-sharing: mem-sharing a range of memory

[Wei Liu]

On Tue, Aug 02, 2016 at 01:17:01PM +0100, Wei Liu wrote:
> On Mon, Aug 01, 2016 at 11:14:27AM -0600, Tamas K Lengyel wrote:
> > Currently mem-sharing can be performed on a page-by-page basis from the control
> > domain. However, this process is quite wasteful when a range of pages have to
> > be deduplicated.
> > 
> > This patch introduces a new mem_sharing memop for range sharing where
> > the user doesn't have to separately nominate each page in both the source and
> > destination domain, and the looping over all pages happen in the hypervisor.
> > This significantly reduces the overhead of sharing a range of memory.
> > 
> > Signed-off-by: Tamas K Lengyel <tamas.lengyel@zentific.com>
> > Acked-by: Wei Liu <wei.liu2@citrix.com>
> > Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
> 
> I notice this patch has got sufficient acks.
> 
> I will queue this up.

Pushed.

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