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Date: Mon, 7 Nov 2011 15:36:13 -0500
From: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: David Vrabel <david.vrabel@...rix.com>,
Jeremy Fitzhardinge <jeremy@...p.org>,
"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
"namhyung@...il.com" <namhyung@...il.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
"rientjes@...gle.com" <rientjes@...gle.com>,
"paulmck@...ux.vnet.ibm.com" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [Xen-devel] Re: [Revert] Re: [PATCH] mm: sync vmalloc address
space page tables in alloc_vm_area()
> > >
> > > oookay, I queued this for 3.1 and tagged it for a 3.0.x backport. I
> > > *think* that's the outcome of this discussion, for the short-term?
> >
> > <nods> Yup. Thanks!
>
> Hey Andrew,
>
> The long term outcome is the patchset that David worked on. I've sent
> a GIT PULL to Linus to pick up the Xen related patches that switch over
> the users of the right API:
>
> (xen) stable/vmalloc-3.2 for Linux 3.2-rc0
>
> (https://lkml.org/lkml/2011/10/29/82)
And Linus picked it up.
.. snip..
>
> Also, not sure what you thought of this patch below?
Patch included as attachment for easier review..
>
> From b9acd3abc12972be0d938d7bc2466d899023e757 Mon Sep 17 00:00:00 2001
> From: David Vrabel <david.vrabel@...rix.com>
> Date: Thu, 29 Sep 2011 16:53:32 +0100
> Subject: [PATCH] xen: map foreign pages for shared rings by updating the PTEs
> directly
>
> When mapping a foreign page with xenbus_map_ring_valloc() with the
> GNTTABOP_map_grant_ref hypercall, set the GNTMAP_contains_pte flag and
> pass a pointer to the PTE (in init_mm).
>
> After the page is mapped, the usual fault mechanism can be used to
> update additional MMs. This allows the vmalloc_sync_all() to be
> removed from alloc_vm_area().
>
> Signed-off-by: David Vrabel <david.vrabel@...rix.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Jeremy Fitzhardinge <jeremy@...p.org>
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> ---
> arch/x86/xen/grant-table.c | 2 +-
> drivers/xen/xenbus/xenbus_client.c | 11 ++++++++---
> include/linux/vmalloc.h | 2 +-
> mm/vmalloc.c | 27 +++++++++++++--------------
> 4 files changed, 23 insertions(+), 19 deletions(-)
>
> diff --git a/arch/x86/xen/grant-table.c b/arch/x86/xen/grant-table.c
> index 6bbfd7a..5a40d24 100644
> --- a/arch/x86/xen/grant-table.c
> +++ b/arch/x86/xen/grant-table.c
> @@ -71,7 +71,7 @@ int arch_gnttab_map_shared(unsigned long *frames, unsigned long nr_gframes,
>
> if (shared == NULL) {
> struct vm_struct *area =
> - alloc_vm_area(PAGE_SIZE * max_nr_gframes);
> + alloc_vm_area(PAGE_SIZE * max_nr_gframes, NULL);
> BUG_ON(area == NULL);
> shared = area->addr;
> *__shared = shared;
> diff --git a/drivers/xen/xenbus/xenbus_client.c b/drivers/xen/xenbus/xenbus_client.c
> index 229d3ad..52bc57f 100644
> --- a/drivers/xen/xenbus/xenbus_client.c
> +++ b/drivers/xen/xenbus/xenbus_client.c
> @@ -34,6 +34,7 @@
> #include <linux/types.h>
> #include <linux/vmalloc.h>
> #include <asm/xen/hypervisor.h>
> +#include <asm/xen/page.h>
> #include <xen/interface/xen.h>
> #include <xen/interface/event_channel.h>
> #include <xen/events.h>
> @@ -435,19 +436,20 @@ EXPORT_SYMBOL_GPL(xenbus_free_evtchn);
> int xenbus_map_ring_valloc(struct xenbus_device *dev, int gnt_ref, void **vaddr)
> {
> struct gnttab_map_grant_ref op = {
> - .flags = GNTMAP_host_map,
> + .flags = GNTMAP_host_map | GNTMAP_contains_pte,
> .ref = gnt_ref,
> .dom = dev->otherend_id,
> };
> struct vm_struct *area;
> + pte_t *pte;
>
> *vaddr = NULL;
>
> - area = alloc_vm_area(PAGE_SIZE);
> + area = alloc_vm_area(PAGE_SIZE, &pte);
> if (!area)
> return -ENOMEM;
>
> - op.host_addr = (unsigned long)area->addr;
> + op.host_addr = arbitrary_virt_to_machine(pte).maddr;
>
> if (HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, &op, 1))
> BUG();
> @@ -526,6 +528,7 @@ int xenbus_unmap_ring_vfree(struct xenbus_device *dev, void *vaddr)
> struct gnttab_unmap_grant_ref op = {
> .host_addr = (unsigned long)vaddr,
> };
> + unsigned int level;
>
> /* It'd be nice if linux/vmalloc.h provided a find_vm_area(void *addr)
> * method so that we don't have to muck with vmalloc internals here.
> @@ -547,6 +550,8 @@ int xenbus_unmap_ring_vfree(struct xenbus_device *dev, void *vaddr)
> }
>
> op.handle = (grant_handle_t)area->phys_addr;
> + op.host_addr = arbitrary_virt_to_machine(
> + lookup_address((unsigned long)vaddr, &level)).maddr;
>
> if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1))
> BUG();
> diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
> index 9332e52..1a77252 100644
> --- a/include/linux/vmalloc.h
> +++ b/include/linux/vmalloc.h
> @@ -118,7 +118,7 @@ unmap_kernel_range(unsigned long addr, unsigned long size)
> #endif
>
> /* Allocate/destroy a 'vmalloc' VM area. */
> -extern struct vm_struct *alloc_vm_area(size_t size);
> +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 */
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 5016f19..b5deec6 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2105,23 +2105,30 @@ void __attribute__((weak)) vmalloc_sync_all(void)
>
> static int f(pte_t *pte, pgtable_t table, unsigned long addr, void *data)
> {
> - /* apply_to_page_range() does all the hard work. */
> + 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 the kernel address space is not shared
> - * between processes, it syncs the pagetable across all
> - * processes.
> + * 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)
> +struct vm_struct *alloc_vm_area(size_t size, pte_t **ptes)
> {
> struct vm_struct *area;
>
> @@ -2135,19 +2142,11 @@ struct vm_struct *alloc_vm_area(size_t size)
> * of kernel virtual address space and mapped into init_mm.
> */
> if (apply_to_page_range(&init_mm, (unsigned long)area->addr,
> - area->size, f, NULL)) {
> + size, f, ptes ? &ptes : NULL)) {
> free_vm_area(area);
> return NULL;
> }
>
> - /*
> - * If the allocated address space is passed to a hypercall
> - * before being used then we cannot rely on a page fault to
> - * trigger an update of the page tables. So sync all the page
> - * tables here.
> - */
> - vmalloc_sync_all();
> -
> return area;
> }
> EXPORT_SYMBOL_GPL(alloc_vm_area);
> --
> 1.7.7.1
>
View attachment "0001-xen-map-foreign-pages-for-shared-rings-by-updating-t.patch" of type "text/plain" (5538 bytes)
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