[Xen-changelog] [xen staging] x86/vmx: use a MEMF_no_refcount domheap page for APIC_DEFAULT_PHYS_BASE

[patchbot@xxxxxxx]

commit ea3daabff5f2be6f5dd5c3f4d6890746c4ec5378
Author:     Paul Durrant <pdurrant@xxxxxxxxxx>
AuthorDate: Fri Jan 24 14:49:35 2020 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Fri Feb 14 14:24:50 2020 +0000

    x86/vmx: use a MEMF_no_refcount domheap page for APIC_DEFAULT_PHYS_BASE
    
    vmx_alloc_vlapic_mapping() currently contains some very odd looking code
    that allocates a MEMF_no_owner domheap page and then shares with the guest
    as if it were a xenheap page. This then requires vmx_free_vlapic_mapping()
    to call a special function in the mm code: free_shared_domheap_page().
    
    By using a MEMF_no_refcount domheap page instead, the odd looking code in
    vmx_alloc_vlapic_mapping() can simply use get_page_and_type() to set up a
    writable mapping before insertion in the P2M and vmx_free_vlapic_mapping()
    can simply release the page using put_page_alloc_ref() followed by
    put_page_and_type(). This then allows free_shared_domheap_page() to be
    purged.
    
    Signed-off-by: Paul Durrant <pdurrant@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
---
 xen/arch/x86/hvm/vmx/vmx.c | 21 ++++++++++++++++++---
 xen/arch/x86/mm.c          | 10 ----------
 xen/include/asm-x86/mm.h   |  2 --
 3 files changed, 18 insertions(+), 15 deletions(-)

diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index f6350daf4b..bc2f48bf2c 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -3029,12 +3029,22 @@ static int vmx_alloc_vlapic_mapping(struct domain *d)
     if ( !cpu_has_vmx_virtualize_apic_accesses )
         return 0;
 
-    pg = alloc_domheap_page(d, MEMF_no_owner);
+    pg = alloc_domheap_page(d, MEMF_no_refcount);
     if ( !pg )
         return -ENOMEM;
+
+    if ( !get_page_and_type(pg, d, PGT_writable_page) )
+    {
+        /*
+         * The domain can't possibly know about this page yet, so failure
+         * here is a clear indication of something fishy going on.
+         */
+        domain_crash(d);
+        return -ENODATA;
+    }
+
     mfn = page_to_mfn(pg);
     clear_domain_page(mfn);
-    share_xen_page_with_guest(pg, d, SHARE_rw);
     d->arch.hvm.vmx.apic_access_mfn = mfn;
 
     return set_mmio_p2m_entry(d, paddr_to_pfn(APIC_DEFAULT_PHYS_BASE), mfn,
@@ -3048,7 +3058,12 @@ static void vmx_free_vlapic_mapping(struct domain *d)
 
     d->arch.hvm.vmx.apic_access_mfn = _mfn(0);
     if ( !mfn_eq(mfn, _mfn(0)) )
-        free_shared_domheap_page(mfn_to_page(mfn));
+    {
+        struct page_info *pg = mfn_to_page(mfn);
+
+        put_page_alloc_ref(pg);
+        put_page_and_type(pg);
+    }
 }
 
 static void vmx_install_vlapic_mapping(struct vcpu *v)
diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index ec0970fef5..edc238e51a 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -502,16 +502,6 @@ void share_xen_page_with_guest(struct page_info *page, 
struct domain *d,
     spin_unlock(&d->page_alloc_lock);
 }
 
-void free_shared_domheap_page(struct page_info *page)
-{
-    put_page_alloc_ref(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, mfn_t mfn)
 {
     struct domain *d = v->domain;
diff --git a/xen/include/asm-x86/mm.h b/xen/include/asm-x86/mm.h
index 06d64d494d..fafb3af46d 100644
--- a/xen/include/asm-x86/mm.h
+++ b/xen/include/asm-x86/mm.h
@@ -320,8 +320,6 @@ struct page_info
 
 #define maddr_get_owner(ma)   (page_get_owner(maddr_to_page((ma))))
 
-extern void free_shared_domheap_page(struct page_info *page);
-
 #define frame_table ((struct page_info *)FRAMETABLE_VIRT_START)
 extern unsigned long max_page;
 extern unsigned long total_pages;
--
generated by git-patchbot for /home/xen/git/xen.git#staging

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