[Xen-devel] [PATCH for-4.10 v2 2/5] tools/dombuilder: Remove clear_page() from xc_dom_boot.c

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

pfn 0 is a legitimate (albeit unlikely) frame to use, so skipping it is wrong.
This behaviour appears to exists simply to cover the fact that zero is the
default value of an uninitialised field in dom.

ARM already clears the frames at the point that the pfns are allocated,
meaning that the added clear_page() is wasteful.  Alter x86 to match ARM and
clear the page when it is allocated.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>
Tested-by: Julien Grall <julien.grall@xxxxxxx>
---
CC: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
CC: Julien Grall <julien.grall@xxxxxxx>
---
 tools/libxc/xc_dom_arm.c  |  3 ++-
 tools/libxc/xc_dom_boot.c | 26 --------------------------
 tools/libxc/xc_dom_x86.c  |  8 ++++++++
 3 files changed, 10 insertions(+), 27 deletions(-)

diff --git a/tools/libxc/xc_dom_arm.c b/tools/libxc/xc_dom_arm.c
index 7c4997a..fce151d 100644
--- a/tools/libxc/xc_dom_arm.c
+++ b/tools/libxc/xc_dom_arm.c
@@ -91,7 +91,8 @@ static int alloc_magic_pages(struct xc_dom_image *dom)
     xc_clear_domain_page(dom->xch, dom->guest_domid, dom->console_pfn);
     xc_clear_domain_page(dom->xch, dom->guest_domid, dom->xenstore_pfn);
     xc_clear_domain_page(dom->xch, dom->guest_domid, base + 
MEMACCESS_PFN_OFFSET);
-    xc_clear_domain_page(dom->xch, dom->guest_domid, base + VUART_PFN_OFFSET);
+    xc_clear_domain_page(dom->xch, dom->guest_domid, dom->vuart_gfn);
+
     xc_hvm_param_set(dom->xch, dom->guest_domid, HVM_PARAM_CONSOLE_PFN,
             dom->console_pfn);
     xc_hvm_param_set(dom->xch, dom->guest_domid, HVM_PARAM_STORE_PFN,
diff --git a/tools/libxc/xc_dom_boot.c b/tools/libxc/xc_dom_boot.c
index 40eb518..2e5681d 100644
--- a/tools/libxc/xc_dom_boot.c
+++ b/tools/libxc/xc_dom_boot.c
@@ -62,25 +62,6 @@ static int setup_hypercall_page(struct xc_dom_image *dom)
     return rc;
 }
 
-static int clear_page(struct xc_dom_image *dom, xen_pfn_t pfn)
-{
-    xen_pfn_t dst;
-    int rc;
-
-    if ( pfn == 0 )
-        return 0;
-
-    dst = xc_dom_p2m(dom, pfn);
-    DOMPRINTF("%s: pfn 0x%" PRIpfn ", mfn 0x%" PRIpfn "",
-              __FUNCTION__, pfn, dst);
-    rc = xc_clear_domain_page(dom->xch, dom->guest_domid, dst);
-    if ( rc != 0 )
-        xc_dom_panic(dom->xch, XC_INTERNAL_ERROR,
-                     "%s: xc_clear_domain_page failed (pfn 0x%" PRIpfn
-                     ", rc=%d)", __FUNCTION__, pfn, rc);
-    return rc;
-}
-
 
 /* ------------------------------------------------------------------------ */
 
@@ -222,13 +203,6 @@ int xc_dom_boot_image(struct xc_dom_image *dom)
         if ( (rc = dom->arch_hooks->setup_pgtables(dom)) != 0 )
             return rc;
 
-    if ( (rc = clear_page(dom, dom->console_pfn)) != 0 )
-        return rc;
-    if ( (rc = clear_page(dom, dom->xenstore_pfn)) != 0 )
-        return rc;
-    if ( (rc = clear_page(dom, dom->vuart_gfn)) != 0 )
-        return rc;
-
     /* start info page */
     if ( dom->arch_hooks->start_info )
         dom->arch_hooks->start_info(dom);
diff --git a/tools/libxc/xc_dom_x86.c b/tools/libxc/xc_dom_x86.c
index 47db218..bff68a0 100644
--- a/tools/libxc/xc_dom_x86.c
+++ b/tools/libxc/xc_dom_x86.c
@@ -543,10 +543,14 @@ static int alloc_magic_pages_pv(struct xc_dom_image *dom)
     dom->xenstore_pfn = xc_dom_alloc_page(dom, "xenstore");
     if ( dom->xenstore_pfn == INVALID_PFN )
         return -1;
+    xc_clear_domain_page(dom->xch, dom->guest_domid,
+                         xc_dom_p2m(dom, dom->xenstore_pfn));
 
     dom->console_pfn = xc_dom_alloc_page(dom, "console");
     if ( dom->console_pfn == INVALID_PFN )
         return -1;
+    xc_clear_domain_page(dom->xch, dom->guest_domid,
+                         xc_dom_p2m(dom, dom->console_pfn));
 
     dom->alloc_bootstack = 1;
 
@@ -696,7 +700,11 @@ static int alloc_magic_pages_hvm(struct xc_dom_image *dom)
                      special_pfn(SPECIALPAGE_IDENT_PT) << PAGE_SHIFT);
 
     dom->console_pfn = special_pfn(SPECIALPAGE_CONSOLE);
+    xc_clear_domain_page(dom->xch, dom->guest_domid, dom->console_pfn);
+
     dom->xenstore_pfn = special_pfn(SPECIALPAGE_XENSTORE);
+    xc_clear_domain_page(dom->xch, dom->guest_domid, dom->xenstore_pfn);
+
     dom->parms.virt_hypercall = -1;
 
     rc = 0;
-- 
2.1.4


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