xen/setup: update VA mapping when releasing memory during setup

In xen_memory_setup(), if a page that is being released has a VA
mapping this must also be updated.  Otherwise, the page will be not
released completely -- it will still be referenced in Xen and won't be
freed util the mapping is removed and this prevents it from being
reallocated at a different PFN.

This was already being done for the ISA memory region in
xen_ident_map_ISA() but on many systems this was omitting a few pages
as many systems marked a few pages below the ISA memory region as
reserved in the e820 map.

This fixes errors such as:

(XEN) page_alloc.c:1148:d0 Over-allocation for domain 0: 2097153 > 2097152
(XEN) memory.c:133:d0 Could not allocate order=0 extent: id=0 memflags=0 (0 of 17)

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

4 files changed, 34 insertions, 32 deletions

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index fe06bf4ef0e3..ac90e5629508 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1308,7 +1308,6 @@ asmlinkage void __init xen_start_kernel(void)
 
         xen_raw_console_write("mapping kernel into physical memory\n");
         pgd = xen_setup_kernel_pagetable(pgd, xen_start_info->nr_pages);
-        xen_ident_map_ISA();
 
         /* Allocate and initialize top and mid mfn levels for p2m structure */
         xen_build_mfn_list_list();
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 91dc2871e336..c9a351925a0c 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1929,29 +1929,6 @@ static void xen_set_fixmap(unsigned idx, phys_addr_t phys, pgprot_t prot)
 #endif
 }
 
-void __init xen_ident_map_ISA(void)
-{
-        unsigned long pa;
-
-        /*
-         * If we're dom0, then linear map the ISA machine addresses into
-         * the kernel's address space.
-         */
-        if (!xen_initial_domain())
-                return;
-
-        xen_raw_printk("Xen: setup ISA identity maps\n");
-
-        for (pa = ISA_START_ADDRESS; pa < ISA_END_ADDRESS; pa += PAGE_SIZE) {
-                pte_t pte = mfn_pte(PFN_DOWN(pa), PAGE_KERNEL_IO);
-
-                if (HYPERVISOR_update_va_mapping(PAGE_OFFSET + pa, pte, 0))
-                        BUG();
-        }
-
-        xen_flush_tlb();
-}
-
 static void __init xen_post_allocator_init(void)
 {
         pv_mmu_ops.set_pte = xen_set_pte;
diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 30ac05a8d28f..3ebba0753d38 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -139,6 +139,13 @@ static unsigned long __init xen_do_chunk(unsigned long start,
 
         return len;
 }
+
+static unsigned long __init xen_release_chunk(unsigned long start,
+                                              unsigned long end)
+{
+        return xen_do_chunk(start, end, true);
+}
+
 static unsigned long __init xen_populate_chunk(
         const struct e820entry *list, size_t map_size,
         unsigned long max_pfn, unsigned long *last_pfn,
@@ -197,6 +204,29 @@ static unsigned long __init xen_populate_chunk(
         }
         return done;
 }
+
+static void __init xen_set_identity_and_release_chunk(
+        unsigned long start_pfn, unsigned long end_pfn, unsigned long nr_pages,
+        unsigned long *released, unsigned long *identity)
+{
+        unsigned long pfn;
+
+        /*
+         * If the PFNs are currently mapped, the VA mapping also needs
+         * to be updated to be 1:1.
+         */
+        for (pfn = start_pfn; pfn <= max_pfn_mapped && pfn < end_pfn; pfn++)
+                (void)HYPERVISOR_update_va_mapping(
+                        (unsigned long)__va(pfn << PAGE_SHIFT),
+                        mfn_pte(pfn, PAGE_KERNEL_IO), 0);
+
+        if (start_pfn < nr_pages)
+                *released += xen_release_chunk(
+                        start_pfn, min(end_pfn, nr_pages));
+
+        *identity += set_phys_range_identity(start_pfn, end_pfn);
+}
+
 static unsigned long __init xen_set_identity_and_release(
         const struct e820entry *list, size_t map_size, unsigned long nr_pages)
 {
@@ -226,14 +256,11 @@ static unsigned long __init xen_set_identity_and_release(
                         if (entry->type == E820_RAM)
                                 end_pfn = PFN_UP(entry->addr);
 
-                        if (start_pfn < end_pfn) {
-                                if (start_pfn < nr_pages)
-                                        released += xen_do_chunk(
-                                                start_pfn, min(end_pfn, nr_pages), true);
+                        if (start_pfn < end_pfn)
+                                xen_set_identity_and_release_chunk(
+                                        start_pfn, end_pfn, nr_pages,
+                                        &released, &identity);
 
-                                identity += set_phys_range_identity(
-                                        start_pfn, end_pfn);
-                        }
                         start = end;
                 }
         }
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index b095739ccd4c..506fa08d934a 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -28,7 +28,6 @@ void xen_setup_shared_info(void);
 void xen_build_mfn_list_list(void);
 void xen_setup_machphys_mapping(void);
 pgd_t *xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn);
-void xen_ident_map_ISA(void);
 void xen_reserve_top(void);
 extern unsigned long xen_max_p2m_pfn;