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SubjectRe: [PATCH 6/6] x86/xen: open code alloc_vm_area in arch_gnttab_valloc
On Mon, Sep 21, 2020 at 04:44:10PM -0400, boris.ostrovsky@oracle.com wrote:
> This will end up incrementing area->ptes pointer. So perhaps something like
>
>
> pte_t **ptes = area->ptes;
>
> if (apply_to_page_range(&init_mm, (unsigned long)area->area->addr,
>                         PAGE_SIZE * nr_frames, gnttab_apply, &ptes)) {
>
>        ...

Yeah. What do you think of this version? I think it is a little
cleaner and matches what xenbus does. At this point it probably should
be split into a Xen and a alloc_vm_area removal patch, though.

---
From 74d6b797e049f72b5e9f63f14da6321c4209a792 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@lst.de>
Date: Wed, 16 Sep 2020 16:09:42 +0200
Subject: x86/xen: open code alloc_vm_area in arch_gnttab_valloc

Open code alloc_vm_area in the last remaining caller.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
arch/x86/xen/grant-table.c | 27 +++++++++++++++------
include/linux/vmalloc.h | 5 +---
mm/nommu.c | 7 ------
mm/vmalloc.c | 48 --------------------------------------
4 files changed, 21 insertions(+), 66 deletions(-)

diff --git a/arch/x86/xen/grant-table.c b/arch/x86/xen/grant-table.c
index 4988e19598c8a5..1e681bf62561a0 100644
--- a/arch/x86/xen/grant-table.c
+++ b/arch/x86/xen/grant-table.c
@@ -25,6 +25,7 @@
static struct gnttab_vm_area {
struct vm_struct *area;
pte_t **ptes;
+ int idx;
} gnttab_shared_vm_area, gnttab_status_vm_area;

int arch_gnttab_map_shared(unsigned long *frames, unsigned long nr_gframes,
@@ -90,19 +91,31 @@ void arch_gnttab_unmap(void *shared, unsigned long nr_gframes)
}
}

+static int gnttab_apply(pte_t *pte, unsigned long addr, void *data)
+{
+ struct gnttab_vm_area *area = data;
+
+ area->ptes[area->idx++] = pte;
+ return 0;
+}
+
static int arch_gnttab_valloc(struct gnttab_vm_area *area, unsigned nr_frames)
{
area->ptes = kmalloc_array(nr_frames, sizeof(*area->ptes), GFP_KERNEL);
if (area->ptes == NULL)
return -ENOMEM;
-
- area->area = alloc_vm_area(PAGE_SIZE * nr_frames, area->ptes);
- if (area->area == NULL) {
- kfree(area->ptes);
- return -ENOMEM;
- }
-
+ area->area = get_vm_area(PAGE_SIZE * nr_frames, VM_IOREMAP);
+ if (!area->area)
+ goto out_free_ptes;
+ if (apply_to_page_range(&init_mm, (unsigned long)area->area->addr,
+ PAGE_SIZE * nr_frames, gnttab_apply, area))
+ goto out_free_vm_area;
return 0;
+out_free_vm_area:
+ free_vm_area(area->area);
+out_free_ptes:
+ kfree(area->ptes);
+ return -ENOMEM;
}

static void arch_gnttab_vfree(struct gnttab_vm_area *area)
diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index 8ecd92a947ee0c..a1a4e2f8163504 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -168,6 +168,7 @@ extern struct vm_struct *__get_vm_area_caller(unsigned long size,
unsigned long flags,
unsigned long start, unsigned long end,
const void *caller);
+void free_vm_area(struct vm_struct *area);
extern struct vm_struct *remove_vm_area(const void *addr);
extern struct vm_struct *find_vm_area(const void *addr);

@@ -203,10 +204,6 @@ static inline void set_vm_flush_reset_perms(void *addr)
}
#endif

-/* Allocate/destroy a 'vmalloc' VM area. */
-extern struct vm_struct *alloc_vm_area(size_t size, pte_t **ptes);
-extern void free_vm_area(struct vm_struct *area);
-
/* for /dev/kmem */
extern long vread(char *buf, char *addr, unsigned long count);
extern long vwrite(char *buf, char *addr, unsigned long count);
diff --git a/mm/nommu.c b/mm/nommu.c
index 75a327149af127..9272f30e4c4726 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -354,13 +354,6 @@ void vm_unmap_aliases(void)
}
EXPORT_SYMBOL_GPL(vm_unmap_aliases);

-struct vm_struct *alloc_vm_area(size_t size, pte_t **ptes)
-{
- BUG();
- return NULL;
-}
-EXPORT_SYMBOL_GPL(alloc_vm_area);
-
void free_vm_area(struct vm_struct *area)
{
BUG();
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 59f2afcf26c312..9f29147deca580 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -3077,54 +3077,6 @@ int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
}
EXPORT_SYMBOL(remap_vmalloc_range);

-static int f(pte_t *pte, unsigned long addr, void *data)
-{
- pte_t ***p = data;
-
- if (p) {
- *(*p) = pte;
- (*p)++;
- }
- return 0;
-}
-
-/**
- * alloc_vm_area - allocate a range of kernel address space
- * @size: size of the area
- * @ptes: returns the PTEs for the address space
- *
- * Returns: NULL on failure, vm_struct on success
- *
- * This function reserves a range of kernel address space, and
- * allocates pagetables to map that range. No actual mappings
- * are created.
- *
- * If @ptes is non-NULL, pointers to the PTEs (in init_mm)
- * allocated for the VM area are returned.
- */
-struct vm_struct *alloc_vm_area(size_t size, pte_t **ptes)
-{
- struct vm_struct *area;
-
- area = get_vm_area_caller(size, VM_IOREMAP,
- __builtin_return_address(0));
- if (area == NULL)
- return NULL;
-
- /*
- * This ensures that page tables are constructed for this region
- * of kernel virtual address space and mapped into init_mm.
- */
- if (apply_to_page_range(&init_mm, (unsigned long)area->addr,
- size, f, ptes ? &ptes : NULL)) {
- free_vm_area(area);
- return NULL;
- }
-
- return area;
-}
-EXPORT_SYMBOL_GPL(alloc_vm_area);
-
void free_vm_area(struct vm_struct *area)
{
struct vm_struct *ret;
--
2.28.0
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