Merge tag 'stable/for-linus-3.6-rc3-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen

Pull three xen bug-fixes from Konrad Rzeszutek Wilk:
 - Revert the kexec fix which caused on non-kexec shutdowns a race.
 - Reuse existing P2M leafs - instead of requiring to allocate a large
   area of bootup virtual address estate.
 - Fix a one-off error when adding PFNs for balloon pages.

* tag 'stable/for-linus-3.6-rc3-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen:
  xen/setup: Fix one-off error when adding for-balloon PFNs to the P2M.
  xen/p2m: Reuse existing P2M leafs if they are filled with 1:1 PFNs or INVALID.
  Revert "xen PVonHVM: move shared_info to MMIO before kexec"

1 files changed, 11 insertions, 107 deletions

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index bf4bda6d3e9a..9642d4a38602 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -31,7 +31,6 @@
 #include <linux/pci.h>
 #include <linux/gfp.h>
 #include <linux/memblock.h>
-#include <linux/syscore_ops.h>
 
 #include <xen/xen.h>
 #include <xen/interface/xen.h>
@@ -1470,130 +1469,38 @@ asmlinkage void __init xen_start_kernel(void)
 #endif
 }
 
-#ifdef CONFIG_XEN_PVHVM
-/*
- * The pfn containing the shared_info is located somewhere in RAM. This
- * will cause trouble if the current kernel is doing a kexec boot into a
- * new kernel. The new kernel (and its startup code) can not know where
- * the pfn is, so it can not reserve the page. The hypervisor will
- * continue to update the pfn, and as a result memory corruption occours
- * in the new kernel.
- *
- * One way to work around this issue is to allocate a page in the
- * xen-platform pci device's BAR memory range. But pci init is done very
- * late and the shared_info page is already in use very early to read
- * the pvclock. So moving the pfn from RAM to MMIO is racy because some
- * code paths on other vcpus could access the pfn during the small
- * window when the old pfn is moved to the new pfn. There is even a
- * small window were the old pfn is not backed by a mfn, and during that
- * time all reads return -1.
- *
- * Because it is not known upfront where the MMIO region is located it
- * can not be used right from the start in xen_hvm_init_shared_info.
- *
- * To minimise trouble the move of the pfn is done shortly before kexec.
- * This does not eliminate the race because all vcpus are still online
- * when the syscore_ops will be called. But hopefully there is no work
- * pending at this point in time. Also the syscore_op is run last which
- * reduces the risk further.
- */
-
-static struct shared_info *xen_hvm_shared_info;
-
-static void xen_hvm_connect_shared_info(unsigned long pfn)
+void __ref xen_hvm_init_shared_info(void)
 {
+        int cpu;
         struct xen_add_to_physmap xatp;
+        static struct shared_info *shared_info_page = 0;
 
+        if (!shared_info_page)
+                shared_info_page = (struct shared_info *)
+                        extend_brk(PAGE_SIZE, PAGE_SIZE);
         xatp.domid = DOMID_SELF;
         xatp.idx = 0;
         xatp.space = XENMAPSPACE_shared_info;
-        xatp.gpfn = pfn;
+        xatp.gpfn = __pa(shared_info_page) >> PAGE_SHIFT;
         if (HYPERVISOR_memory_op(XENMEM_add_to_physmap, &xatp))
                 BUG();
 
-}
-static void xen_hvm_set_shared_info(struct shared_info *sip)
-{
-        int cpu;
-
-        HYPERVISOR_shared_info = sip;
+        HYPERVISOR_shared_info = (struct shared_info *)shared_info_page;
 
         /* xen_vcpu is a pointer to the vcpu_info struct in the shared_info
          * page, we use it in the event channel upcall and in some pvclock
          * related functions. We don't need the vcpu_info placement
          * optimizations because we don't use any pv_mmu or pv_irq op on
          * HVM.
-         * When xen_hvm_set_shared_info is run at boot time only vcpu 0 is
-         * online but xen_hvm_set_shared_info is run at resume time too and
+         * When xen_hvm_init_shared_info is run at boot time only vcpu 0 is
+         * online but xen_hvm_init_shared_info is run at resume time too and
          * in that case multiple vcpus might be online. */
         for_each_online_cpu(cpu) {
                 per_cpu(xen_vcpu, cpu) = &HYPERVISOR_shared_info->vcpu_info[cpu];
         }
 }
 
-/* Reconnect the shared_info pfn to a mfn */
-void xen_hvm_resume_shared_info(void)
-{
-        xen_hvm_connect_shared_info(__pa(xen_hvm_shared_info) >> PAGE_SHIFT);
-}
-
-#ifdef CONFIG_KEXEC
-static struct shared_info *xen_hvm_shared_info_kexec;
-static unsigned long xen_hvm_shared_info_pfn_kexec;
-
-/* Remember a pfn in MMIO space for kexec reboot */
-void __devinit xen_hvm_prepare_kexec(struct shared_info *sip, unsigned long pfn)
-{
-        xen_hvm_shared_info_kexec = sip;
-        xen_hvm_shared_info_pfn_kexec = pfn;
-}
-
-static void xen_hvm_syscore_shutdown(void)
-{
-        struct xen_memory_reservation reservation = {
-                .domid = DOMID_SELF,
-                .nr_extents = 1,
-        };
-        unsigned long prev_pfn;
-        int rc;
-
-        if (!xen_hvm_shared_info_kexec)
-                return;
-
-        prev_pfn = __pa(xen_hvm_shared_info) >> PAGE_SHIFT;
-        set_xen_guest_handle(reservation.extent_start, &prev_pfn);
-
-        /* Move pfn to MMIO, disconnects previous pfn from mfn */
-        xen_hvm_connect_shared_info(xen_hvm_shared_info_pfn_kexec);
-
-        /* Update pointers, following hypercall is also a memory barrier */
-        xen_hvm_set_shared_info(xen_hvm_shared_info_kexec);
-
-        /* Allocate new mfn for previous pfn */
-        do {
-                rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
-                if (rc == 0)
-                        msleep(123);
-        } while (rc == 0);
-
-        /* Make sure the previous pfn is really connected to a (new) mfn */
-        BUG_ON(rc != 1);
-}
-
-static struct syscore_ops xen_hvm_syscore_ops = {
-        .shutdown = xen_hvm_syscore_shutdown,
-};
-#endif
-
-/* Use a pfn in RAM, may move to MMIO before kexec. */
-static void __init xen_hvm_init_shared_info(void)
-{
-        /* Remember pointer for resume */
-        xen_hvm_shared_info = extend_brk(PAGE_SIZE, PAGE_SIZE);
-        xen_hvm_connect_shared_info(__pa(xen_hvm_shared_info) >> PAGE_SHIFT);
-        xen_hvm_set_shared_info(xen_hvm_shared_info);
-}
-
+#ifdef CONFIG_XEN_PVHVM
 static void __init init_hvm_pv_info(void)
 {
         int major, minor;
@@ -1644,9 +1551,6 @@ static void __init xen_hvm_guest_init(void)
         init_hvm_pv_info();
 
         xen_hvm_init_shared_info();
-#ifdef CONFIG_KEXEC
-        register_syscore_ops(&xen_hvm_syscore_ops);
-#endif
 
         if (xen_feature(XENFEAT_hvm_callback_vector))
                 xen_have_vector_callback = 1;