Hi Penny,
On 18/05/2021 06:21, Penny Zheng wrote:
Static Allocation refers to system or sub-system(domains) for which memory
areas are pre-defined by configuration using physical address ranges.
Those pre-defined memory, -- Static Momery, as parts of RAM reserved in the
s/Momery/Memory/
beginning, shall never go to heap allocator or boot allocator for any use.
Domains on Static Allocation is supported through device tree property
`xen,static-mem` specifying reserved RAM banks as this domain's guest RAM.
By default, they shall be mapped to the fixed guest RAM address
`GUEST_RAM0_BASE`, `GUEST_RAM1_BASE`.
This patch introduces this new `xen,static-mem` property to define static
memory nodes in device tree file.
This patch also documents and parses this new attribute at boot time and
stores related info in static_mem for later initialization.
Signed-off-by: Penny Zheng <penny.zh...@arm.com>
---
docs/misc/arm/device-tree/booting.txt | 33 +++++++++++++++++
xen/arch/arm/bootfdt.c | 52 +++++++++++++++++++++++++++
xen/include/asm-arm/setup.h | 2 ++
3 files changed, 87 insertions(+)
diff --git a/docs/misc/arm/device-tree/booting.txt
b/docs/misc/arm/device-tree/booting.txt
index 5243bc7fd3..d209149d71 100644
--- a/docs/misc/arm/device-tree/booting.txt
+++ b/docs/misc/arm/device-tree/booting.txt
@@ -268,3 +268,36 @@ The DTB fragment is loaded at 0xc000000 in the example
above. It should
follow the convention explained in docs/misc/arm/passthrough.txt. The
DTB fragment will be added to the guest device tree, so that the guest
kernel will be able to discover the device.
+
+
+Static Allocation
+=============
+
+Static Allocation refers to system or sub-system(domains) for which memory
+areas are pre-defined by configuration using physical address ranges.
+Those pre-defined memory, -- Static Momery, as parts of RAM reserved in the
s/Momery/Memory/
+beginning, shall never go to heap allocator or boot allocator for any use.
+
+Domains on Static Allocation is supported through device tree property
+`xen,static-mem` specifying reserved RAM banks as this domain's guest RAM.
I would suggest to use "physical RAM" when you refer to the host memory.
+By default, they shall be mapped to the fixed guest RAM address
+`GUEST_RAM0_BASE`, `GUEST_RAM1_BASE`.
There are a few bits that needs to clarified or part of the description:
1) "By default" suggests there is an alternative possibility.
However, I don't see any.
2) Will the first region of xen,static-mem be mapped to
GUEST_RAM0_BASE and the second to GUEST_RAM1_BASE? What if a third
region is specificed?
3) We don't guarantee the base address and the size of the banks.
Wouldn't it be better to let the admin select the region he/she wants?
4) How do you determine the number of cells for the address and the size?
+Static Allocation is only supported on AArch64 for now.
The code doesn't seem to be AArch64 specific. So why can't this be used
for 32-bit Arm?
+
+The dtb property should look like as follows:
+
+ chosen {
+ domU1 {
+ compatible = "xen,domain";
+ #address-cells = <0x2>;
+ #size-cells = <0x2>;
+ cpus = <2>;
+ xen,static-mem = <0x0 0x30000000 0x0 0x20000000>;
+
+ ...
+ };
+ };
+
+DOMU1 on Static Allocation has reserved RAM bank at 0x30000000 of 512MB size
Do you mean "DomU1 will have a static memory of 512MB reserved from the
physical address..."?
+as guest RAM.
diff --git a/xen/arch/arm/bootfdt.c b/xen/arch/arm/bootfdt.c
index dcff512648..e9f14e6a44 100644
--- a/xen/arch/arm/bootfdt.c
+++ b/xen/arch/arm/bootfdt.c
@@ -327,6 +327,55 @@ static void __init process_chosen_node(const void *fdt,
int node,
add_boot_module(BOOTMOD_RAMDISK, start, end-start, false);
}
+static int __init process_static_memory(const void *fdt, int node,
+ const char *name,
+ u32 address_cells, u32 size_cells,
+ void *data)
+{
+ int i;
+ int banks;
+ const __be32 *cell;
+ paddr_t start, size;
+ u32 reg_cells = address_cells + size_cells;
+ struct meminfo *mem = data;
+ const struct fdt_property *prop;
+
+ if ( address_cells < 1 || size_cells < 1 )
+ {
+ printk("fdt: invalid #address-cells or #size-cells for static memory");
+ return -EINVAL;
+ }
+
+ /*
+ * Check if static memory property belongs to a specific domain, that is,
+ * its node `domUx` has compatible string "xen,domain".
+ */
+ if ( fdt_node_check_compatible(fdt, node, "xen,domain") != 0 )
+ printk("xen,static-mem property can only locate under /domUx node.\n");
+
+ prop = fdt_get_property(fdt, node, name, NULL);
+ if ( !prop )
+ return -ENOENT;
+
+ cell = (const __be32 *)prop->data;
+ banks = fdt32_to_cpu(prop->len) / (reg_cells * sizeof (u32));
+
+ for ( i = 0; i < banks && mem->nr_banks < NR_MEM_BANKS; i++ )
+ {
+ device_tree_get_reg(&cell, address_cells, size_cells, &start, &size);
+ /* Some DT may describe empty bank, ignore them */
+ if ( !size )
+ continue;
+ mem->bank[mem->nr_banks].start = start;
+ mem->bank[mem->nr_banks].size = size;
+ mem->nr_banks++;
+ }
+
+ if ( i < banks )
+ return -ENOSPC;
+ return 0;
+}
+
static int __init early_scan_node(const void *fdt,
int node, const char *name, int depth,
u32 address_cells, u32 size_cells,
@@ -345,6 +394,9 @@ static int __init early_scan_node(const void *fdt,
process_multiboot_node(fdt, node, name, address_cells, size_cells);
else if ( depth == 1 && device_tree_node_matches(fdt, node, "chosen") )
process_chosen_node(fdt, node, name, address_cells, size_cells);
+ else if ( depth == 2 && fdt_get_property(fdt, node, "xen,static-mem",
NULL) )
+ process_static_memory(fdt, node, "xen,static-mem", address_cells,
+ size_cells, &bootinfo.static_mem);
I am a bit concerned to add yet another method to parse the DT and all
the extra code it will add like in patch #2.
From the host PoV, they are memory reserved for a specific purpose.
Would it be possible to consider the reserve-memory binding for that
purpose? This will happen outside of chosen, but we could use a phandle
to refer the region.
if ( rc < 0 )
printk("fdt: node `%s': parsing failed\n", name);
diff --git a/xen/include/asm-arm/setup.h b/xen/include/asm-arm/setup.h
index 5283244015..5e9f296760 100644
--- a/xen/include/asm-arm/setup.h
+++ b/xen/include/asm-arm/setup.h
@@ -74,6 +74,8 @@ struct bootinfo {
#ifdef CONFIG_ACPI
struct meminfo acpi;
#endif
+ /* Static Memory */
+ struct meminfo static_mem;
};
extern struct bootinfo bootinfo;
Cheers,
--
Julien Grall