[Xen-devel] [PATCH 2/4] libxc: support of linear p2m list for migration of pv-domains

[Juergen Gross <jgross@xxxxxxxx>]

In order to be able to migrate pv-domains with more than 512 GB of RAM
the p2m information can be specified by the guest kernel via a virtual
mapped linear p2m list instead of a 3 level tree.

Add support for this new p2m format in libxc.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 tools/libxc/xc_sr_save_x86_pv.c | 139 +++++++++++++++++++++++++++++++++++++++-
 1 file changed, 136 insertions(+), 3 deletions(-)

diff --git a/tools/libxc/xc_sr_save_x86_pv.c b/tools/libxc/xc_sr_save_x86_pv.c
index d7acd37..0237378 100644
--- a/tools/libxc/xc_sr_save_x86_pv.c
+++ b/tools/libxc/xc_sr_save_x86_pv.c
@@ -116,7 +116,7 @@ static int map_p2m_leaves(struct xc_sr_context *ctx, 
xen_pfn_t *mfns,
  * frames making up the guests p2m table.  Construct a list of pfns making up
  * the table.
  */
-static int map_p2m(struct xc_sr_context *ctx)
+static int map_p2m_tree(struct xc_sr_context *ctx)
 {
     /* Terminology:
      *
@@ -138,8 +138,6 @@ static int map_p2m(struct xc_sr_context *ctx)
     void *guest_fl = NULL;
     size_t local_fl_size;
 
-    ctx->x86_pv.max_pfn = GET_FIELD(ctx->x86_pv.shinfo, arch.max_pfn,
-                                    ctx->x86_pv.width) - 1;
     fpp = PAGE_SIZE / ctx->x86_pv.width;
     fll_entries = (ctx->x86_pv.max_pfn / (fpp * fpp)) + 1;
     if ( fll_entries > fpp )
@@ -270,6 +268,141 @@ err:
 }
 
 /*
+ * Map the guest p2m frames specified via a cr3 value, a virtual address, and
+ * the maximum pfn.
+ */
+static int map_p2m_list(struct xc_sr_context *ctx, uint64_t p2m_cr3)
+{
+    xc_interface *xch = ctx->xch;
+    xen_vaddr_t p2m_vaddr, p2m_end, mask, off;
+    xen_pfn_t p2m_mfn, mfn, saved_mfn, max_pfn;
+    uint64_t *ptes;
+    xen_pfn_t *mfns;
+    unsigned fpp, n_pages, level, shift, idx_start, idx_end, idx, saved_idx;
+    int rc = -1;
+
+    p2m_mfn = cr3_to_mfn(ctx, p2m_cr3);
+    if ( p2m_mfn == 0 || p2m_mfn > ctx->x86_pv.max_mfn )
+    {
+        ERROR("Bad p2m_cr3 value %#lx", p2m_cr3);
+        errno = ERANGE;
+        return -1;
+    }
+
+    p2m_vaddr = GET_FIELD(ctx->x86_pv.shinfo, arch.p2m_vaddr,
+                          ctx->x86_pv.width);
+    fpp = PAGE_SIZE / ctx->x86_pv.width;
+    ctx->x86_pv.p2m_frames = (ctx->x86_pv.max_pfn + fpp) / fpp;
+    p2m_end = p2m_vaddr + ctx->x86_pv.p2m_frames * PAGE_SIZE - 1;
+    DPRINTF("p2m list from %#lx to %#lx, root at %#lx", p2m_vaddr, p2m_end,
+            p2m_mfn);
+    DPRINTF("max_pfn %#lx, p2m_frames %d", ctx->x86_pv.max_pfn,
+            ctx->x86_pv.p2m_frames);
+
+    mask = (ctx->x86_pv.width == 8) ?
+           0x0000ffffffffffffULL : 0x00000000ffffffffULL;
+
+    mfns = malloc(sizeof(*mfns));
+    if ( !mfns )
+    {
+        ERROR("Cannot allocate memory for array of %u mfns", 1);
+        goto err;
+    }
+    mfns[0] = p2m_mfn;
+    off = 0;
+    saved_mfn = 0;
+    idx_start = idx_end = saved_idx = 0;
+
+    for ( level = ctx->x86_pv.levels; level > 0; level-- )
+    {
+        n_pages = idx_end - idx_start + 1;
+        ptes = xc_map_foreign_pages(xch, ctx->domid, PROT_READ, mfns, n_pages);
+        if ( !ptes )
+        {
+            PERROR("Failed to map %u page table pages for p2m list", n_pages);
+            goto err;
+        }
+        free(mfns);
+
+        shift = level * 9 + 3;
+        idx_start = ((p2m_vaddr - off) & mask) >> shift;
+        idx_end = ((p2m_end - off) & mask) >> shift;
+        idx = idx_end - idx_start + 1;
+        mfns = malloc(sizeof(*mfns) * idx);
+        if ( !mfns )
+        {
+            ERROR("Cannot allocate memory for array of %u mfns", idx);
+            goto err;
+        }
+
+        for ( idx = idx_start; idx <= idx_end; idx++ )
+        {
+            mfn = pte_to_frame(ptes[idx]);
+            if ( mfn == 0 || mfn > ctx->x86_pv.max_mfn )
+            {
+                ERROR("Bad mfn %#lx during page table walk for vaddr %#lx at 
level %d of p2m list",
+                      mfn, off + ((xen_vaddr_t)idx << shift), level);
+                errno = ERANGE;
+                goto err;
+            }
+            mfns[idx - idx_start] = mfn;
+
+            /* Maximum pfn check at level 2. Same reasoning as for p2m tree. */
+            if ( level == 2 )
+            {
+                if ( mfn != saved_mfn )
+                {
+                    saved_mfn = mfn;
+                    saved_idx = idx - idx_start;
+                }
+            }
+        }
+
+        if ( level == 2 )
+        {
+            max_pfn = ((xen_pfn_t)saved_idx << 9) * fpp - 1;
+            if ( max_pfn < ctx->x86_pv.max_pfn )
+            {
+                ctx->x86_pv.max_pfn = max_pfn;
+                ctx->x86_pv.p2m_frames = (ctx->x86_pv.max_pfn + fpp) / fpp;
+                p2m_end = p2m_vaddr + ctx->x86_pv.p2m_frames * PAGE_SIZE - 1;
+                idx_end = idx_start + saved_idx;
+            }
+        }
+
+        munmap(ptes, n_pages * PAGE_SIZE);
+        ptes = NULL;
+        off = p2m_vaddr & ((mask >> shift) << shift);
+    }
+
+    /* Map the p2m leaves themselves. */
+    rc = map_p2m_leaves(ctx, mfns, idx_end - idx_start + 1);
+
+err:
+    free(mfns);
+    if ( ptes )
+        munmap(ptes, n_pages * PAGE_SIZE);
+
+    return rc;
+}
+
+/*
+ * Map the guest p2m frames.
+ * Depending on guest support this might either be a virtual mapped linear
+ * list (preferred format) or a 3 level tree linked via mfns.
+ */
+static int map_p2m(struct xc_sr_context *ctx)
+{
+    uint64_t p2m_cr3;
+
+    ctx->x86_pv.max_pfn = GET_FIELD(ctx->x86_pv.shinfo, arch.max_pfn,
+                                    ctx->x86_pv.width) - 1;
+    p2m_cr3 = GET_FIELD(ctx->x86_pv.shinfo, arch.p2m_cr3, ctx->x86_pv.width);
+
+    return p2m_cr3 ? map_p2m_list(ctx, p2m_cr3) : map_p2m_tree(ctx);
+}
+
+/*
  * Obtain a specific vcpus basic state and write an X86_PV_VCPU_BASIC record
  * into the stream.  Performs mfn->pfn conversion on architectural state.
  */
-- 
2.6.2


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