Attachment 146761 Details for Bug 222467 – [XEN]: Enable shadow before memory reservation for HVM

[patch] [XEN]: Enable shadow before memory reservation for HVM

p (text/plain), 5.28 KB, created by Herbert Xu on 2007-01-28 10:57:35 UTC

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Creator: Herbert Xu

Created: 2007-01-28 10:57:35 UTC

Size: 5.28 KB

patch

obsolete

>From: Herbert Xu <herbert.xu@redhat.com>
>To: virtualist@redhat.com
>Subject: Re: [XEN]: Enable shadow before memory reservation for HVM
>Cc: virtualist@redhat.com
>Fcc: =sent
>Organization: Core
>In-Reply-To: <20070127052138.GA13865@gondor.apana.org.au>
>
>Herbert Xu <herbert.xu@redhat.com> wrote:
>> 
>> This patch fixes the "cannot allocate memory" error when starting HVM
>> guests.  The cause of this is that shadow mode is enabled after memory
>> allocation for the guest and before the physmap is filled.
>> 
>> It turns out that the bogus m2p entries are a recent introduction.  When
>> shadow2 (changeset 11151) was introduced, upstream moved the code that enables
>> shadow mode for HVM guests to user-space.  In particular, this was done after
>> memory allocation and before the physmap has been populated.  This only
>> affected HVM because PV translate mode populated the physmap before enabling
>> shadow mode.
>> 
>> Upstream has since fixed it by moving the enabling of shadow mode back into the
>> hypervisor which means that it will occur before memory allocation.  This patch
>> tries to do this in a more conservative way by simply moving the enabling of
>> shadow mode before memory allocation.
>> 
>> I've verified that running this version of xend allows me to start HVM guests
>> on a host where otherwise you can't start HVM guests at all due to this bug.
>> 
>> When we move to 3.0.4 we can remove this patch.
>
>Sorry guys but there was actually a bug in this patch.  I added the
>shadow_enable call to the generic path without checking whether the
>guest is HVM.
>
>Here is a corrected and tested version.
>
>diff -ur xen-3.0.3_0-src.orig/tools/libxc/xc_hvm_build.c xen-3.0.3_0-src/tools/libxc/xc_hvm_build.c
>--- xen-3.0.3_0-src.orig/tools/libxc/xc_hvm_build.c	2006-10-15 22:22:03.000000000 +1000
>+++ xen-3.0.3_0-src/tools/libxc/xc_hvm_build.c	2007-01-27 15:46:43.000000000 +1100
>@@ -441,18 +441,6 @@
>         goto error_out;
>     }
> 
>-    /* HVM domains must be put into shadow mode at the start of day */
>-    if ( xc_shadow_control(xc_handle, domid, XEN_DOMCTL_SHADOW_OP_ENABLE,
>-                           NULL, 0, NULL, 
>-                           XEN_DOMCTL_SHADOW_ENABLE_REFCOUNT  |
>-                           XEN_DOMCTL_SHADOW_ENABLE_TRANSLATE |
>-                           XEN_DOMCTL_SHADOW_ENABLE_EXTERNAL, 
>-                           NULL) )
>-    {
>-        PERROR("Could not enable shadow paging for domain.\n");
>-        goto error_out;
>-    }        
>-
>     memset(ctxt, 0, sizeof(*ctxt));
> 
>     ctxt->flags = VGCF_HVM_GUEST;
>diff -ur xen-3.0.3_0-src.orig/tools/python/xen/lowlevel/xc/xc.c xen-3.0.3_0-src/tools/python/xen/lowlevel/xc/xc.c
>--- xen-3.0.3_0-src.orig/tools/python/xen/lowlevel/xc/xc.c	2007-01-23 22:51:50.000000000 +1100
>+++ xen-3.0.3_0-src/tools/python/xen/lowlevel/xc/xc.c	2007-01-27 15:40:48.000000000 +1100
>@@ -647,6 +647,31 @@
>     return Py_BuildValue("i", mbarg);
> }
> 
>+static PyObject *pyxc_hvm_shadow_enable(PyObject *self,
>+                                    PyObject *args,
>+                                    PyObject *kwds)
>+{
>+    XcObject *xc = (XcObject *)self;
>+
>+    uint32_t dom;
>+
>+    static char *kwd_list[] = { "dom", NULL };
>+
>+    if ( !PyArg_ParseTupleAndKeywords(args, kwds, "i", kwd_list, &dom) )
>+        return NULL;
>+
>+    if ( xc_shadow_control(xc->xc_handle, dom, XEN_DOMCTL_SHADOW_OP_ENABLE,
>+                           NULL, 0, NULL, 
>+                           XEN_DOMCTL_SHADOW_ENABLE_REFCOUNT  |
>+                           XEN_DOMCTL_SHADOW_ENABLE_TRANSLATE |
>+                           XEN_DOMCTL_SHADOW_ENABLE_EXTERNAL, 
>+                           NULL) )
>+        return PyErr_SetFromErrno(xc_error);
>+    
>+    Py_INCREF(zero);
>+    return zero;
>+}
>+
> static PyObject *pyxc_sched_credit_domain_set(XcObject *self,
>                                               PyObject *args,
>                                               PyObject *kwds)
>@@ -1089,6 +1114,13 @@
>       " mb [int, -1]: MB of shadow memory this domain should have.\n\n"
>       "Returns: [int] MB of shadow memory in use by this domain.\n" },
> 
>+    { "hvm_shadow_enable", 
>+      (PyCFunction)pyxc_hvm_shadow_enable, 
>+      METH_VARARGS | METH_KEYWORDS, "\n"
>+      "Enable shadow pagetable\n"
>+      " dom [int]:   Identifier of domain.\n\n"
>+      "Returns: [int] 0 on success; -1 on error.\n" },
>+
>     { "domain_setmaxmem", 
>       (PyCFunction)pyxc_domain_setmaxmem, 
>       METH_VARARGS, "\n"
>diff -ur xen-3.0.3_0-src.orig/tools/python/xen/xend/XendDomainInfo.py xen-3.0.3_0-src/tools/python/xen/xend/XendDomainInfo.py
>--- xen-3.0.3_0-src.orig/tools/python/xen/xend/XendDomainInfo.py	2007-01-23 22:51:50.000000000 +1100
>+++ xen-3.0.3_0-src/tools/python/xen/xend/XendDomainInfo.py	2007-01-28 21:47:26.000000000 +1100
>@@ -1349,6 +1349,9 @@
>             shadow_cur = xc.shadow_mem_control(self.domid, shadow / 1024)
>             self.info['shadow_memory'] = shadow_cur
> 
>+            if self.image.ostype == "hvm":
>+                xc.hvm_shadow_enable(self.domid);
>+
>             # initial memory reservation
>             xc.domain_memory_increase_reservation(self.domid, reservation, 0,
>                                                   0)
>
>Cheers,
>-- 
>Visit Openswan at http://www.openswan.org/
>Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
>Home Page: http://gondor.apana.org.au/~herbert/
>PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

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Attachments on bug 222467: 146739 | 146761