[Xen-changelog] [xen master] VMX: allocate APIC access page from domain heap

[patchbot@xxxxxxx]

commit a2b4b8c20413302c0983b730925d59dc2fee3bb3
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Mon Dec 21 13:35:13 2015 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Dec 21 13:35:13 2015 +0100

    VMX: allocate APIC access page from domain heap
    
    ... since we don't need its virtual address anywhere (it's a
    placeholder page only after all). For this to work (and possibly be
    done elsewhere too) share_xen_page_with_guest() needs to mark pages
    handed to it as Xen heap ones.
    
    To be on the safe side, also explicitly clear the page (not having done
    so was okay due to the XSA-100 fix, but is still a latent bug since we
    don't formally guarantee allocations to come out zeroed, and in fact
    this property may disappear again as soon as the asynchronous runtime
    scrubbing patches arrive).
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Acked-by: Kevin Tian <kevin.tian@xxxxxxxxx>
---
 xen/arch/x86/hvm/vmx/vmx.c |   20 ++++++++++++--------
 xen/arch/x86/mm.c          |   13 ++++++++++++-
 xen/include/asm-x86/mm.h   |    1 +
 3 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 2922673..e056515 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -2489,18 +2489,21 @@ gp_fault:
 
 static int vmx_alloc_vlapic_mapping(struct domain *d)
 {
-    void *apic_va;
+    struct page_info *pg;
+    unsigned long mfn;
 
     if ( !cpu_has_vmx_virtualize_apic_accesses )
         return 0;
 
-    apic_va = alloc_xenheap_page();
-    if ( apic_va == NULL )
+    pg = alloc_domheap_page(d, MEMF_no_owner);
+    if ( !pg )
         return -ENOMEM;
-    share_xen_page_with_guest(virt_to_page(apic_va), d, XENSHARE_writable);
-    d->arch.hvm_domain.vmx.apic_access_mfn = virt_to_mfn(apic_va);
-    set_mmio_p2m_entry(d, paddr_to_pfn(APIC_DEFAULT_PHYS_BASE),
-        _mfn(virt_to_mfn(apic_va)), p2m_get_hostp2m(d)->default_access);
+    mfn = page_to_mfn(pg);
+    clear_domain_page(_mfn(mfn));
+    share_xen_page_with_guest(pg, d, XENSHARE_writable);
+    d->arch.hvm_domain.vmx.apic_access_mfn = mfn;
+    set_mmio_p2m_entry(d, paddr_to_pfn(APIC_DEFAULT_PHYS_BASE), _mfn(mfn),
+                       p2m_get_hostp2m(d)->default_access);
 
     return 0;
 }
@@ -2508,8 +2511,9 @@ static int vmx_alloc_vlapic_mapping(struct domain *d)
 static void vmx_free_vlapic_mapping(struct domain *d)
 {
     unsigned long mfn = d->arch.hvm_domain.vmx.apic_access_mfn;
+
     if ( mfn != 0 )
-        free_xenheap_page(mfn_to_virt(mfn));
+        free_shared_domheap_page(mfn_to_page(mfn));
 }
 
 static void vmx_install_vlapic_mapping(struct vcpu *v)
diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 92df36f..d33eb10 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -454,7 +454,7 @@ void share_xen_page_with_guest(
     /* Only add to the allocation list if the domain isn't dying. */
     if ( !d->is_dying )
     {
-        page->count_info |= PGC_allocated | 1;
+        page->count_info |= PGC_xen_heap | PGC_allocated | 1;
         if ( unlikely(d->xenheap_pages++ == 0) )
             get_knownalive_domain(d);
         page_list_add_tail(page, &d->xenpage_list);
@@ -469,6 +469,17 @@ void share_xen_page_with_privileged_guests(
     share_xen_page_with_guest(page, dom_xen, readonly);
 }
 
+void free_shared_domheap_page(struct page_info *page)
+{
+    if ( test_and_clear_bit(_PGC_allocated, &page->count_info) )
+        put_page(page);
+    if ( !test_and_clear_bit(_PGC_xen_heap, &page->count_info) )
+        ASSERT_UNREACHABLE();
+    page->u.inuse.type_info = 0;
+    page_set_owner(page, NULL);
+    free_domheap_page(page);
+}
+
 void make_cr3(struct vcpu *v, unsigned long mfn)
 {
     v->arch.cr3 = mfn << PAGE_SHIFT;
diff --git a/xen/include/asm-x86/mm.h b/xen/include/asm-x86/mm.h
index 67b34c6..1f5e335 100644
--- a/xen/include/asm-x86/mm.h
+++ b/xen/include/asm-x86/mm.h
@@ -276,6 +276,7 @@ extern void share_xen_page_with_guest(
     struct page_info *page, struct domain *d, int readonly);
 extern void share_xen_page_with_privileged_guests(
     struct page_info *page, int readonly);
+extern void free_shared_domheap_page(struct page_info *page);
 
 #define frame_table ((struct page_info *)FRAMETABLE_VIRT_START)
 #define spage_table ((struct spage_info *)SPAGETABLE_VIRT_START)
--
generated by git-patchbot for /home/xen/git/xen.git#master

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