Feature:

- Register a pfn_is_ram helper to speed up reading of /proc/vmcore.
 Bug-fixes:
  - Three pvops call for Xen were undefined causing BUG_ONs.
  - Add a quirk so that the shutdown watches (used by kdump) are not used with older Xen (3.4).
  - Fix ungraceful state transition for the HVC console.
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Merge tag 'stable/for-linus-3.7-rc0-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen

Pull Xen fixes from Konrad Rzeszutek Wilk:
 "This has four bug-fixes and one tiny feature that I forgot to put
  initially in my tree due to oversight.

  The feature is for kdump kernels to speed up the /proc/vmcore reading.
  There is a ram_is_pfn helper function that the different platforms can
  register for.  We are now doing that.

  The bug-fixes cover some embarrassing struct pv_cpu_ops variables
  being set to NULL on Xen (but not baremetal).  We had a similar issue
  in the past with {write|read}_msr_safe and this fills the three
  missing ones.  The other bug-fix is to make the console output (hvc)
  be capable of dealing with misbehaving backends and not fall flat on
  its face.  Lastly, a quirk for older XenBus implementations that came
  with an ancient v3.4 hypervisor (so RHEL5 based) - reading of certain
  non-existent attributes just hangs the guest during bootup - so we
  take precaution of not doing that on such older installations.

  Feature:
   - Register a pfn_is_ram helper to speed up reading of /proc/vmcore.
  Bug-fixes:
   - Three pvops call for Xen were undefined causing BUG_ONs.
   - Add a quirk so that the shutdown watches (used by kdump) are not
     used with older Xen (3.4).
   - Fix ungraceful state transition for the HVC console."

* tag 'stable/for-linus-3.7-rc0-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen:
  xen/pv-on-hvm kexec: add quirk for Xen 3.4 and shutdown watches.
  xen/bootup: allow {read|write}_cr8 pvops call.
  xen/bootup: allow read_tscp call for Xen PV guests.
  xen pv-on-hvm: add pfn_is_ram helper for kdump
  xen/hvc: handle backend CLOSED without CLOSING

arch/x86/xen/enlighten.c

@@ -987,7 +987,16 @@ static void xen_write_cr4(unsigned long cr4)
 
 	native_write_cr4(cr4);
 }
-
+#ifdef CONFIG_X86_64
+static inline unsigned long xen_read_cr8(void)
+{
+	return 0;
+}
+static inline void xen_write_cr8(unsigned long val)
+{
+	BUG_ON(val);
+}
+#endif
 static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)
 {
 	int ret;
@@ -1156,6 +1165,11 @@ static const struct pv_cpu_ops xen_cpu_ops __initconst = {
 	.read_cr4_safe = native_read_cr4_safe,
 	.write_cr4 = xen_write_cr4,
 
+#ifdef CONFIG_X86_64
+	.read_cr8 = xen_read_cr8,
+	.write_cr8 = xen_write_cr8,
+#endif
+
 	.wbinvd = native_wbinvd,
 
 	.read_msr = native_read_msr_safe,
@@ -1164,6 +1178,8 @@ static const struct pv_cpu_ops xen_cpu_ops __initconst = {
 	.read_tsc = native_read_tsc,
 	.read_pmc = native_read_pmc,
 
+	.read_tscp = native_read_tscp,
+
 	.iret = xen_iret,
 	.irq_enable_sysexit = xen_sysexit,
 #ifdef CONFIG_X86_64

arch/x86/xen/mmu.c

@@ -47,6 +47,7 @@
 #include <linux/gfp.h>
 #include <linux/memblock.h>
 #include <linux/seq_file.h>
+#include <linux/crash_dump.h>
 
 #include <trace/events/xen.h>
 
@@ -2381,6 +2382,43 @@ void xen_destroy_contiguous_region(unsigned long vstart, unsigned int order)
 EXPORT_SYMBOL_GPL(xen_destroy_contiguous_region);
 
 #ifdef CONFIG_XEN_PVHVM
+#ifdef CONFIG_PROC_VMCORE
+/*
+ * This function is used in two contexts:
+ * - the kdump kernel has to check whether a pfn of the crashed kernel
+ *   was a ballooned page. vmcore is using this function to decide
+ *   whether to access a pfn of the crashed kernel.
+ * - the kexec kernel has to check whether a pfn was ballooned by the
+ *   previous kernel. If the pfn is ballooned, handle it properly.
+ * Returns 0 if the pfn is not backed by a RAM page, the caller may
+ * handle the pfn special in this case.
+ */
+static int xen_oldmem_pfn_is_ram(unsigned long pfn)
+{
+	struct xen_hvm_get_mem_type a = {
+		.domid = DOMID_SELF,
+		.pfn = pfn,
+	};
+	int ram;
+
+	if (HYPERVISOR_hvm_op(HVMOP_get_mem_type, &a))
+		return -ENXIO;
+
+	switch (a.mem_type) {
+		case HVMMEM_mmio_dm:
+			ram = 0;
+			break;
+		case HVMMEM_ram_rw:
+		case HVMMEM_ram_ro:
+		default:
+			ram = 1;
+			break;
+	}
+
+	return ram;
+}
+#endif
+
 static void xen_hvm_exit_mmap(struct mm_struct *mm)
 {
 	struct xen_hvm_pagetable_dying a;
@@ -2411,6 +2449,9 @@ void __init xen_hvm_init_mmu_ops(void)
 {
 	if (is_pagetable_dying_supported())
 		pv_mmu_ops.exit_mmap = xen_hvm_exit_mmap;
+#ifdef CONFIG_PROC_VMCORE
+	register_oldmem_pfn_is_ram(&xen_oldmem_pfn_is_ram);
+#endif
 }
 #endif
 

drivers/tty/hvc/hvc_xen.c

@@ -478,7 +478,6 @@ static void xencons_backend_changed(struct xenbus_device *dev,
 	case XenbusStateInitialising:
 	case XenbusStateInitialised:
 	case XenbusStateUnknown:
-	case XenbusStateClosed:
 		break;
 
 	case XenbusStateInitWait:
@@ -488,6 +487,10 @@ static void xencons_backend_changed(struct xenbus_device *dev,
 		xenbus_switch_state(dev, XenbusStateConnected);
 		break;
 
+	case XenbusStateClosed:
+		if (dev->state == XenbusStateClosed)
+			break;
+		/* Missed the backend's CLOSING state -- fallthrough */
 	case XenbusStateClosing:
 		xenbus_frontend_closed(dev);
 		break;

drivers/xen/xenbus/xenbus_xs.c

@@ -48,6 +48,7 @@
 #include <xen/xenbus.h>
 #include <xen/xen.h>
 #include "xenbus_comms.h"
+#include <asm/xen/hypervisor.h>
 
 struct xs_stored_msg {
 	struct list_head list;
@@ -618,7 +619,24 @@ static struct xenbus_watch *find_watch(const char *token)
 
 	return NULL;
 }
+/*
+ * Certain older XenBus toolstack cannot handle reading values that are
+ * not populated. Some Xen 3.4 installation are incapable of doing this
+ * so if we are running on anything older than 4 do not attempt to read
+ * control/platform-feature-xs_reset_watches.
+ */
+static bool xen_strict_xenbus_quirk()
+{
+	uint32_t eax, ebx, ecx, edx, base;
 
+	base = xen_cpuid_base();
+	cpuid(base + 1, &eax, &ebx, &ecx, &edx);
+
+	if ((eax >> 16) < 4)
+		return true;
+	return false;
+
+}
 static void xs_reset_watches(void)
 {
 	int err, supported = 0;
@@ -626,6 +644,9 @@ static void xs_reset_watches(void)
 	if (!xen_hvm_domain() || xen_initial_domain())
 		return;
 
+	if (xen_strict_xenbus_quirk())
+		return;
+
 	err = xenbus_scanf(XBT_NIL, "control",
 			"platform-feature-xs_reset_watches", "%d", &supported);
 	if (err != 1 || !supported)

include/xen/interface/hvm/hvm_op.h

@@ -43,4 +43,23 @@ struct xen_hvm_pagetable_dying {
 typedef struct xen_hvm_pagetable_dying xen_hvm_pagetable_dying_t;
 DEFINE_GUEST_HANDLE_STRUCT(xen_hvm_pagetable_dying_t);
  
+enum hvmmem_type_t {
+    HVMMEM_ram_rw,             /* Normal read/write guest RAM */
+    HVMMEM_ram_ro,             /* Read-only; writes are discarded */
+    HVMMEM_mmio_dm,            /* Reads and write go to the device model */
+};
+
+#define HVMOP_get_mem_type    15
+/* Return hvmmem_type_t for the specified pfn. */
+struct xen_hvm_get_mem_type {
+    /* Domain to be queried. */
+    domid_t domid;
+    /* OUT variable. */
+    uint16_t mem_type;
+    uint16_t pad[2]; /* align next field on 8-byte boundary */
+    /* IN variable. */
+    uint64_t pfn;
+};
+DEFINE_GUEST_HANDLE_STRUCT(xen_hvm_get_mem_type);
+
 #endif /* __XEN_PUBLIC_HVM_HVM_OP_H__ */