xen: fixes for 4.19-rc2

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Merge tag 'for-linus-4.19b-rc2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

Pull xen fixes from Juergen Gross:

 - minor cleanup avoiding a warning when building with new gcc

 - a patch to add a new sysfs node for Xen frontend/backend drivers to
   make it easier to obtain the state of a pv device

 - two fixes for 32-bit pv-guests to avoid intermediate L1TF vulnerable
   PTEs

* tag 'for-linus-4.19b-rc2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  x86/xen: remove redundant variable save_pud
  xen: export device state to sysfs
  x86/pae: use 64 bit atomic xchg function in native_ptep_get_and_clear
  x86/xen: don't write ptes directly in 32-bit PV guests

Documentation/ABI/stable/sysfs-bus-xen-backend

@@ -73,3 +73,12 @@ KernelVersion:	3.0
 Contact:	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
 Description:
                 Number of sectors written by the frontend.
+
+What:		/sys/bus/xen-backend/devices/*/state
+Date:		August 2018
+KernelVersion:	4.19
+Contact:	Joe Jin <joe.jin@oracle.com>
+Description:
+                The state of the device. One of: 'Unknown',
+                'Initialising', 'Initialised', 'Connected', 'Closing',
+                'Closed', 'Reconfiguring', 'Reconfigured'.

arch/x86/include/asm/pgtable-3level.h

@@ -2,6 +2,8 @@
 #ifndef _ASM_X86_PGTABLE_3LEVEL_H
 #define _ASM_X86_PGTABLE_3LEVEL_H
 
+#include <asm/atomic64_32.h>
+
 /*
  * Intel Physical Address Extension (PAE) Mode - three-level page
  * tables on PPro+ CPUs.
@@ -150,10 +152,7 @@ static inline pte_t native_ptep_get_and_clear(pte_t *ptep)
 {
 	pte_t res;
 
-	/* xchg acts as a barrier before the setting of the high bits */
+	res.pte = (pteval_t)arch_atomic64_xchg((atomic64_t *)ptep, 0);
-	res.pte_low = xchg(&ptep->pte_low, 0);
-	res.pte_high = ptep->pte_high;
-	ptep->pte_high = 0;
 
 	return res;
 }

arch/x86/xen/mmu_pv.c

@@ -435,14 +435,13 @@ static void xen_set_pud(pud_t *ptr, pud_t val)
 static void xen_set_pte_atomic(pte_t *ptep, pte_t pte)
 {
 	trace_xen_mmu_set_pte_atomic(ptep, pte);
-	set_64bit((u64 *)ptep, native_pte_val(pte));
+	__xen_set_pte(ptep, pte);
 }
 
 static void xen_pte_clear(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
 {
 	trace_xen_mmu_pte_clear(mm, addr, ptep);
-	if (!xen_batched_set_pte(ptep, native_make_pte(0)))
+	__xen_set_pte(ptep, native_make_pte(0));
-		native_pte_clear(mm, addr, ptep);
 }
 
 static void xen_pmd_clear(pmd_t *pmdp)
@@ -1570,7 +1569,7 @@ static void __init xen_set_pte_init(pte_t *ptep, pte_t pte)
 		pte = __pte_ma(((pte_val_ma(*ptep) & _PAGE_RW) | ~_PAGE_RW) &
 			       pte_val_ma(pte));
 #endif
-	native_set_pte(ptep, pte);
+	__xen_set_pte(ptep, pte);
 }
 
 /* Early in boot, while setting up the initial pagetable, assume
@@ -2061,7 +2060,6 @@ void __init xen_relocate_p2m(void)
 	pud_t *pud;
 	pgd_t *pgd;
 	unsigned long *new_p2m;
-	int save_pud;
 
 	size = PAGE_ALIGN(xen_start_info->nr_pages * sizeof(unsigned long));
 	n_pte = roundup(size, PAGE_SIZE) >> PAGE_SHIFT;
@@ -2091,7 +2089,6 @@ void __init xen_relocate_p2m(void)
 
 	pgd = __va(read_cr3_pa());
 	new_p2m = (unsigned long *)(2 * PGDIR_SIZE);
-	save_pud = n_pud;
 	for (idx_pud = 0; idx_pud < n_pud; idx_pud++) {
 		pud = early_memremap(pud_phys, PAGE_SIZE);
 		clear_page(pud);

drivers/xen/xenbus/xenbus_probe.c

@@ -402,10 +402,19 @@ static ssize_t modalias_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(modalias);
 
+static ssize_t state_show(struct device *dev,
+			    struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%s\n",
+			xenbus_strstate(to_xenbus_device(dev)->state));
+}
+static DEVICE_ATTR_RO(state);
+
 static struct attribute *xenbus_dev_attrs[] = {
 	&dev_attr_nodename.attr,
 	&dev_attr_devtype.attr,
 	&dev_attr_modalias.attr,
+	&dev_attr_state.attr,
 	NULL,
 };