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-rw-r--r--arch/x86/xen/enlighten.c118
-rw-r--r--arch/x86/xen/suspend.c2
-rw-r--r--arch/x86/xen/xen-ops.h2
3 files changed, 109 insertions, 13 deletions
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index f1814fc2cb7..a6f8acbdfc9 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -31,6 +31,7 @@
#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>
@@ -1471,38 +1472,130 @@ asmlinkage void __init xen_start_kernel(void)
#endif
}
-void __ref xen_hvm_init_shared_info(void)
+#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)
{
- 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 = __pa(shared_info_page) >> PAGE_SHIFT;
+ xatp.gpfn = pfn;
if (HYPERVISOR_memory_op(XENMEM_add_to_physmap, &xatp))
BUG();
- HYPERVISOR_shared_info = (struct shared_info *)shared_info_page;
+}
+static void xen_hvm_set_shared_info(struct shared_info *sip)
+{
+ int cpu;
+
+ HYPERVISOR_shared_info = sip;
/* 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_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
+ * 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
* in that case multiple vcpus might be online. */
for_each_online_cpu(cpu) {
per_cpu(xen_vcpu, cpu) = &HYPERVISOR_shared_info->vcpu_info[cpu];
}
}
-#ifdef CONFIG_XEN_PVHVM
+/* 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);
+}
+
static void __init init_hvm_pv_info(void)
{
int major, minor;
@@ -1553,6 +1646,9 @@ 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;
diff --git a/arch/x86/xen/suspend.c b/arch/x86/xen/suspend.c
index 45329c8c226..ae8a00c39de 100644
--- a/arch/x86/xen/suspend.c
+++ b/arch/x86/xen/suspend.c
@@ -30,7 +30,7 @@ void xen_arch_hvm_post_suspend(int suspend_cancelled)
{
#ifdef CONFIG_XEN_PVHVM
int cpu;
- xen_hvm_init_shared_info();
+ xen_hvm_resume_shared_info();
xen_callback_vector();
xen_unplug_emulated_devices();
if (xen_feature(XENFEAT_hvm_safe_pvclock)) {
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index 202d4c15015..1e4329e04e0 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -41,7 +41,7 @@ void xen_enable_syscall(void);
void xen_vcpu_restore(void);
void xen_callback_vector(void);
-void xen_hvm_init_shared_info(void);
+void xen_hvm_resume_shared_info(void);
void xen_unplug_emulated_devices(void);
void __init xen_build_dynamic_phys_to_machine(void);