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authorOleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>2021-12-09 22:05:34 +0200
committerJuergen Gross <jgross@suse.com>2022-01-06 09:53:38 +0100
commitd1a928eac72962b562162c25baf45ce147e27247 (patch)
tree8fc44cbedd4f423cb931b5924932e548dd024625 /drivers/xen
parent9dd060afe2dfd4e3f67b6732fdc681e52cd7cbd9 (diff)
xen/unpopulated-alloc: Add mechanism to use Xen resource
The main reason of this change is that unpopulated-alloc code cannot be used in its current form on Arm, but there is a desire to reuse it to avoid wasting real RAM pages for the grant/foreign mappings. The problem is that system "iomem_resource" is used for the address space allocation, but the really unallocated space can't be figured out precisely by the domain on Arm without hypervisor involvement. For example, not all device I/O regions are known by the time domain starts creating grant/foreign mappings. And following the advise from "iomem_resource" we might end up reusing these regions by a mistake. So, the hypervisor which maintains the P2M for the domain is in the best position to provide unused regions of guest physical address space which could be safely used to create grant/foreign mappings. Introduce new helper arch_xen_unpopulated_init() which purpose is to create specific Xen resource based on the memory regions provided by the hypervisor to be used as unused space for Xen scratch pages. If arch doesn't define arch_xen_unpopulated_init() the default "iomem_resource" will be used. Update the arguments list of allocate_resource() in fill_list() to always allocate a region from the hotpluggable range (maximum possible addressable physical memory range for which the linear mapping could be created). If arch doesn't define arch_get_mappable_range() the default range (0,-1) will be used. The behaviour on x86 won't be changed by current patch as both arch_xen_unpopulated_init() and arch_get_mappable_range() are not implemented for it. Also fallback to allocate xenballooned pages (balloon out RAM pages) if we do not have any suitable resource to work with (target_resource is invalid) and as the result we won't be able to provide unpopulated pages on a request. Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org> Link: https://lore.kernel.org/r/1639080336-26573-5-git-send-email-olekstysh@gmail.com Signed-off-by: Juergen Gross <jgross@suse.com>
Diffstat (limited to 'drivers/xen')
-rw-r--r--drivers/xen/unpopulated-alloc.c86
1 files changed, 82 insertions, 4 deletions
diff --git a/drivers/xen/unpopulated-alloc.c b/drivers/xen/unpopulated-alloc.c
index a03dc5b1f37b..a8b41057c382 100644
--- a/drivers/xen/unpopulated-alloc.c
+++ b/drivers/xen/unpopulated-alloc.c
@@ -8,6 +8,7 @@
#include <asm/page.h>
+#include <xen/balloon.h>
#include <xen/page.h>
#include <xen/xen.h>
@@ -15,13 +16,29 @@ static DEFINE_MUTEX(list_lock);
static struct page *page_list;
static unsigned int list_count;
+static struct resource *target_resource;
+
+/*
+ * If arch is not happy with system "iomem_resource" being used for
+ * the region allocation it can provide it's own view by creating specific
+ * Xen resource with unused regions of guest physical address space provided
+ * by the hypervisor.
+ */
+int __weak __init arch_xen_unpopulated_init(struct resource **res)
+{
+ *res = &iomem_resource;
+
+ return 0;
+}
+
static int fill_list(unsigned int nr_pages)
{
struct dev_pagemap *pgmap;
- struct resource *res;
+ struct resource *res, *tmp_res = NULL;
void *vaddr;
unsigned int i, alloc_pages = round_up(nr_pages, PAGES_PER_SECTION);
- int ret = -ENOMEM;
+ struct range mhp_range;
+ int ret;
res = kzalloc(sizeof(*res), GFP_KERNEL);
if (!res)
@@ -30,14 +47,40 @@ static int fill_list(unsigned int nr_pages)
res->name = "Xen scratch";
res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
- ret = allocate_resource(&iomem_resource, res,
- alloc_pages * PAGE_SIZE, 0, -1,
+ mhp_range = mhp_get_pluggable_range(true);
+
+ ret = allocate_resource(target_resource, res,
+ alloc_pages * PAGE_SIZE, mhp_range.start, mhp_range.end,
PAGES_PER_SECTION * PAGE_SIZE, NULL, NULL);
if (ret < 0) {
pr_err("Cannot allocate new IOMEM resource\n");
goto err_resource;
}
+ /*
+ * Reserve the region previously allocated from Xen resource to avoid
+ * re-using it by someone else.
+ */
+ if (target_resource != &iomem_resource) {
+ tmp_res = kzalloc(sizeof(*tmp_res), GFP_KERNEL);
+ if (!tmp_res) {
+ ret = -ENOMEM;
+ goto err_insert;
+ }
+
+ tmp_res->name = res->name;
+ tmp_res->start = res->start;
+ tmp_res->end = res->end;
+ tmp_res->flags = res->flags;
+
+ ret = request_resource(&iomem_resource, tmp_res);
+ if (ret < 0) {
+ pr_err("Cannot request resource %pR (%d)\n", tmp_res, ret);
+ kfree(tmp_res);
+ goto err_insert;
+ }
+ }
+
pgmap = kzalloc(sizeof(*pgmap), GFP_KERNEL);
if (!pgmap) {
ret = -ENOMEM;
@@ -95,6 +138,11 @@ static int fill_list(unsigned int nr_pages)
err_memremap:
kfree(pgmap);
err_pgmap:
+ if (tmp_res) {
+ release_resource(tmp_res);
+ kfree(tmp_res);
+ }
+err_insert:
release_resource(res);
err_resource:
kfree(res);
@@ -112,6 +160,14 @@ int xen_alloc_unpopulated_pages(unsigned int nr_pages, struct page **pages)
unsigned int i;
int ret = 0;
+ /*
+ * Fallback to default behavior if we do not have any suitable resource
+ * to allocate required region from and as the result we won't be able to
+ * construct pages.
+ */
+ if (!target_resource)
+ return xen_alloc_ballooned_pages(nr_pages, pages);
+
mutex_lock(&list_lock);
if (list_count < nr_pages) {
ret = fill_list(nr_pages - list_count);
@@ -159,6 +215,11 @@ void xen_free_unpopulated_pages(unsigned int nr_pages, struct page **pages)
{
unsigned int i;
+ if (!target_resource) {
+ xen_free_ballooned_pages(nr_pages, pages);
+ return;
+ }
+
mutex_lock(&list_lock);
for (i = 0; i < nr_pages; i++) {
pages[i]->zone_device_data = page_list;
@@ -201,3 +262,20 @@ static int __init init(void)
}
subsys_initcall(init);
#endif
+
+static int __init unpopulated_init(void)
+{
+ int ret;
+
+ if (!xen_domain())
+ return -ENODEV;
+
+ ret = arch_xen_unpopulated_init(&target_resource);
+ if (ret) {
+ pr_err("xen:unpopulated: Cannot initialize target resource\n");
+ target_resource = NULL;
+ }
+
+ return ret;
+}
+early_initcall(unpopulated_init);