xen/grant: Implement an grant frame array struct (v3).

The 'xen_hvm_resume_frames' used to be an 'unsigned long'
and contain the virtual address of the grants. That was OK
for most architectures (PVHVM, ARM) were the grants are contiguous
in memory. That however is not the case for PVH - in which case
we will have to do a lookup for each virtual address for the PFN.

Instead of doing that, lets make it a structure which will contain
the array of PFNs, the virtual address and the count of said PFNs.

Also provide a generic functions: gnttab_setup_auto_xlat_frames and
gnttab_free_auto_xlat_frames to populate said structure with
appropriate values for PVHVM and ARM.

To round it off, change the name from 'xen_hvm_resume_frames' to
a more descriptive one - 'xen_auto_xlat_grant_frames'.

For PVH, in patch "xen/pvh: Piggyback on PVHVM for grant driver"
we will populate the 'xen_auto_xlat_grant_frames' by ourselves.

v2 moves the xen_remap in the gnttab_setup_auto_xlat_frames
and also introduces xen_unmap for gnttab_free_auto_xlat_frames.

Suggested-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
[v3: Based on top of 'asm/xen/page.h: remove redundant semicolon']
Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

arch/arm/include/asm/xen/page.h

@@ -118,5 +118,6 @@ static inline bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 }
 
 #define xen_remap(cookie, size) ioremap_cached((cookie), (size))
+#define xen_unmap(cookie) iounmap((cookie))
 
 #endif /* _ASM_ARM_XEN_PAGE_H */

arch/arm/xen/enlighten.c

@@ -208,6 +208,7 @@ static int __init xen_guest_init(void)
 	const char *version = NULL;
 	const char *xen_prefix = "xen,xen-";
 	struct resource res;
+	unsigned long grant_frames;
 
 	node = of_find_compatible_node(NULL, NULL, "xen,xen");
 	if (!node) {
@@ -224,10 +225,10 @@ static int __init xen_guest_init(void)
 	}
 	if (of_address_to_resource(node, GRANT_TABLE_PHYSADDR, &res))
 		return 0;
-	xen_hvm_resume_frames = res.start;
+	grant_frames = res.start;
 	xen_events_irq = irq_of_parse_and_map(node, 0);
 	pr_info("Xen %s support found, events_irq=%d gnttab_frame_pfn=%lx\n",
-			version, xen_events_irq, (xen_hvm_resume_frames >> PAGE_SHIFT));
+			version, xen_events_irq, (grant_frames >> PAGE_SHIFT));
 	xen_domain_type = XEN_HVM_DOMAIN;
 
 	xen_setup_features();
@@ -265,6 +266,10 @@ static int __init xen_guest_init(void)
 	if (xen_vcpu_info == NULL)
 		return -ENOMEM;
 
+	if (gnttab_setup_auto_xlat_frames(grant_frames)) {
+		free_percpu(xen_vcpu_info);
+		return -ENOMEM;
+	}
 	gnttab_init();
 	if (!xen_initial_domain())
 		xenbus_probe(NULL);

arch/x86/include/asm/xen/page.h

@@ -227,5 +227,6 @@ void make_lowmem_page_readonly(void *vaddr);
 void make_lowmem_page_readwrite(void *vaddr);
 
 #define xen_remap(cookie, size) ioremap((cookie), (size));
+#define xen_unmap(cookie) iounmap((cookie))
 
 #endif /* _ASM_X86_XEN_PAGE_H */

drivers/xen/grant-table.c

@@ -65,8 +65,7 @@ static unsigned int nr_grant_frames;
 static int gnttab_free_count;
 static grant_ref_t gnttab_free_head;
 static DEFINE_SPINLOCK(gnttab_list_lock);
-unsigned long xen_hvm_resume_frames;
-EXPORT_SYMBOL_GPL(xen_hvm_resume_frames);
+struct grant_frames xen_auto_xlat_grant_frames;
 
 static union {
 	struct grant_entry_v1 *v1;
@@ -838,6 +837,51 @@ unsigned int gnttab_max_grant_frames(void)
 }
 EXPORT_SYMBOL_GPL(gnttab_max_grant_frames);
 
+int gnttab_setup_auto_xlat_frames(unsigned long addr)
+{
+	xen_pfn_t *pfn;
+	unsigned int max_nr_gframes = __max_nr_grant_frames();
+	unsigned int i;
+	void *vaddr;
+
+	if (xen_auto_xlat_grant_frames.count)
+		return -EINVAL;
+
+	vaddr = xen_remap(addr, PAGE_SIZE * max_nr_gframes);
+	if (vaddr == NULL) {
+		pr_warn("Failed to ioremap gnttab share frames (addr=0x%08lx)!\n",
+			addr);
+		return -ENOMEM;
+	}
+	pfn = kcalloc(max_nr_gframes, sizeof(pfn[0]), GFP_KERNEL);
+	if (!pfn) {
+		xen_unmap(vaddr);
+		return -ENOMEM;
+	}
+	for (i = 0; i < max_nr_gframes; i++)
+		pfn[i] = PFN_DOWN(addr) + i;
+
+	xen_auto_xlat_grant_frames.vaddr = vaddr;
+	xen_auto_xlat_grant_frames.pfn = pfn;
+	xen_auto_xlat_grant_frames.count = max_nr_gframes;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(gnttab_setup_auto_xlat_frames);
+
+void gnttab_free_auto_xlat_frames(void)
+{
+	if (!xen_auto_xlat_grant_frames.count)
+		return;
+	kfree(xen_auto_xlat_grant_frames.pfn);
+	xen_unmap(xen_auto_xlat_grant_frames.vaddr);
+
+	xen_auto_xlat_grant_frames.pfn = NULL;
+	xen_auto_xlat_grant_frames.count = 0;
+	xen_auto_xlat_grant_frames.vaddr = NULL;
+}
+EXPORT_SYMBOL_GPL(gnttab_free_auto_xlat_frames);
+
 /* Handling of paged out grant targets (GNTST_eagain) */
 #define MAX_DELAY 256
 static inline void
@@ -1068,6 +1112,7 @@ static int gnttab_map(unsigned int start_idx, unsigned int end_idx)
 		struct xen_add_to_physmap xatp;
 		unsigned int i = end_idx;
 		rc = 0;
+		BUG_ON(xen_auto_xlat_grant_frames.count < nr_gframes);
 		/*
 		 * Loop backwards, so that the first hypercall has the largest
 		 * index, ensuring that the table will grow only once.
@@ -1076,7 +1121,7 @@ static int gnttab_map(unsigned int start_idx, unsigned int end_idx)
 			xatp.domid = DOMID_SELF;
 			xatp.idx = i;
 			xatp.space = XENMAPSPACE_grant_table;
-			xatp.gpfn = (xen_hvm_resume_frames >> PAGE_SHIFT) + i;
+			xatp.gpfn = xen_auto_xlat_grant_frames.pfn[i];
 			rc = HYPERVISOR_memory_op(XENMEM_add_to_physmap, &xatp);
 			if (rc != 0) {
 				pr_warn("grant table add_to_physmap failed, err=%d\n",
@@ -1174,11 +1219,10 @@ static int gnttab_setup(void)
 		return -ENOSYS;
 
 	if (xen_feature(XENFEAT_auto_translated_physmap) && gnttab_shared.addr == NULL) {
-		gnttab_shared.addr = xen_remap(xen_hvm_resume_frames,
-						PAGE_SIZE * max_nr_gframes);
+		gnttab_shared.addr = xen_auto_xlat_grant_frames.vaddr;
 		if (gnttab_shared.addr == NULL) {
-			pr_warn("Failed to ioremap gnttab share frames (addr=0x%08lx)!\n",
-					xen_hvm_resume_frames);
+			pr_warn("gnttab share frames (addr=0x%08lx) is not mapped!\n",
+				(unsigned long)xen_auto_xlat_grant_frames.vaddr);
 			return -ENOMEM;
 		}
 	}

drivers/xen/platform-pci.c

@@ -108,6 +108,7 @@ static int platform_pci_init(struct pci_dev *pdev,
 	long ioaddr;
 	long mmio_addr, mmio_len;
 	unsigned int max_nr_gframes;
+	unsigned long grant_frames;
 
 	if (!xen_domain())
 		return -ENODEV;
@@ -154,13 +155,16 @@ static int platform_pci_init(struct pci_dev *pdev,
 	}
 
 	max_nr_gframes = gnttab_max_grant_frames();
-	xen_hvm_resume_frames = alloc_xen_mmio(PAGE_SIZE * max_nr_gframes);
+	grant_frames = alloc_xen_mmio(PAGE_SIZE * max_nr_gframes);
+	if (gnttab_setup_auto_xlat_frames(grant_frames))
+		goto out;
 	ret = gnttab_init();
 	if (ret)
-		goto out;
+		goto grant_out;
 	xenbus_probe(NULL);
 	return 0;
-
+grant_out:
+	gnttab_free_auto_xlat_frames();
 out:
 	pci_release_region(pdev, 0);
 mem_out:

include/xen/grant_table.h

@@ -178,8 +178,15 @@ int arch_gnttab_map_status(uint64_t *frames, unsigned long nr_gframes,
 			   grant_status_t **__shared);
 void arch_gnttab_unmap(void *shared, unsigned long nr_gframes);
 
-extern unsigned long xen_hvm_resume_frames;
+struct grant_frames {
+	xen_pfn_t *pfn;
+	unsigned int count;
+	void *vaddr;
+};
+extern struct grant_frames xen_auto_xlat_grant_frames;
 unsigned int gnttab_max_grant_frames(void);
+int gnttab_setup_auto_xlat_frames(unsigned long addr);
+void gnttab_free_auto_xlat_frames(void);
 
 #define gnttab_map_vaddr(map) ((void *)(map.host_virt_addr))