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Re: [Xen-devel] [PATCH v3 3/6] xen/arm: keep track of reserved-memory regions
Hi,
On 6/22/19 12:56 AM, Stefano Stabellini wrote:
As we parse the device tree in Xen, keep track of the reserved-memory
regions as they need special treatment (follow-up patches will make use
of the stored information.)
Reuse process_memory_node to add reserved-memory regions to the
bootinfo.reserved_mem array.
Refuse to continue once we reach the max number of reserved memory
regions to avoid accidentally mapping any portions of them into a VM.
Signed-off-by: Stefano Stabellini <stefanos@xxxxxxxxxx>
---
It is cleaner to avoid sharing the whole function process_memory_node
between the normal memory case and the reserved-memory case. I'll do it
in the next version once I understand the best way do to it.
parse_reg(....)
{
if (reg not present)
return -ENOPRESENT
/* parse regs */
return (full) ? -EFULL : 0;
}
process_memory_node(....)
{
return parse_reg(...);
}
process_reserved_region()
{
ret = parse_reg(...);
if ( ret == -EFULL )
panic(....);
else if ( ret != -ENOPRESENT )
return ret;
return 0;
}
---
Changes in v3:
- match only /reserved-memory
- put the warning back in place for reg not present on a normal memory
region
- refuse to continue once we reach the max number of reserved memory
regions
Changes in v2:
- call process_memory_node from process_reserved_memory_node to avoid
duplication
---
xen/arch/arm/bootfdt.c | 38 +++++++++++++++++++++++++++++++------
xen/include/asm-arm/setup.h | 1 +
2 files changed, 33 insertions(+), 6 deletions(-)
diff --git a/xen/arch/arm/bootfdt.c b/xen/arch/arm/bootfdt.c
index 611724433b..b24ab10cb9 100644
--- a/xen/arch/arm/bootfdt.c
+++ b/xen/arch/arm/bootfdt.c
@@ -135,6 +135,8 @@ static int __init process_memory_node(const void *fdt, int
node,
const __be32 *cell;
paddr_t start, size;
u32 reg_cells = address_cells + size_cells;
+ struct meminfo *mem;
+ bool reserved = (bool)data;
if ( address_cells < 1 || size_cells < 1 )
{
@@ -143,29 +145,49 @@ static int __init process_memory_node(const void *fdt,
int node,
return 0;
}
+ if ( reserved )
+ mem = &bootinfo.reserved_mem;
+ else
+ mem = &bootinfo.mem;
Rather than passing a bool, you could pass bootinfo.{mem, reserved_mem}
in parameter.
+
prop = fdt_get_property(fdt, node, "reg", NULL);
if ( !prop )
{
- printk("fdt: node `%s': missing `reg' property\n", name);
+ if ( !reserved )
+ printk("fdt: node `%s': missing `reg' property\n", name);
I would just get rid of this print and return an error than allow the
caller to decide what to do.
return 0;
}
cell = (const __be32 *)prop->data;
banks = fdt32_to_cpu(prop->len) / (reg_cells * sizeof (u32));
- for ( i = 0; i < banks && bootinfo.mem.nr_banks < NR_MEM_BANKS; i++ )
+ for ( i = 0; i < banks && mem->nr_banks < NR_MEM_BANKS; i++ )
{
device_tree_get_reg(&cell, address_cells, size_cells, &start, &size);
if ( !size )
continue;
- bootinfo.mem.bank[bootinfo.mem.nr_banks].start = start;
- bootinfo.mem.bank[bootinfo.mem.nr_banks].size = size;
- bootinfo.mem.nr_banks++;
+ mem->bank[mem->nr_banks].start = start;
+ mem->bank[mem->nr_banks].size = size;
+ mem->nr_banks++;
}
+ /*
+ * We reached the max number of supported reserved-memory regions.
+ * Stop and refuse to continue. We don't want to risk Xen allocating
+ * those regions as normal memory to a VM.
The last sentence is confusing because reserved-region are normal memory
that have been carved out for a specific usage. Also, the problem is not
only with VM but any memory allocation.
So a better sentence would be: "We don't want to give the pages to the
allocator".
+ */
+ BUG_ON(reserved && mem->nr_banks == NR_MEM_BANKS);
return 0;
}
+static int __init process_reserved_memory_node(const void *fdt, int node,
+ const char *name, int depth,
+ u32 address_cells, u32
size_cells)
+{
+ device_tree_for_each_node(fdt, node, depth, process_memory_node,
(void*)true);
+ return 0;
+}
+
static void __init process_multiboot_node(const void *fdt, int node,
const char *name,
u32 address_cells, u32 size_cells)
@@ -299,7 +321,11 @@ static int __init early_scan_node(const void *fdt,
if ( device_tree_node_matches(fdt, node, "memory") )
rc = process_memory_node(fdt, node, name, depth,
- address_cells, size_cells, NULL);
+ address_cells, size_cells, (void*)false);
+ else if ( depth == 1 && !strcmp(name, "reserved-memory") &&
+ strlen(name) == strlen("reserved-memory") )
+ rc = process_reserved_memory_node(fdt, node, name, depth,
+ address_cells, size_cells);
else if ( depth <= 3 && (device_tree_node_compatible(fdt, node,
"xen,multiboot-module" ) ||
device_tree_node_compatible(fdt, node, "multiboot,module" )))
process_multiboot_node(fdt, node, name, address_cells, size_cells);
diff --git a/xen/include/asm-arm/setup.h b/xen/include/asm-arm/setup.h
index 8bf3d5910a..efcba545c2 100644
--- a/xen/include/asm-arm/setup.h
+++ b/xen/include/asm-arm/setup.h
@@ -66,6 +66,7 @@ struct bootcmdlines {
struct bootinfo {
struct meminfo mem;
+ struct meminfo reserved_mem;
struct bootmodules modules;
struct bootcmdlines cmdlines;
#ifdef CONFIG_ACPI
Cheers,
--
Julien Grall
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