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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH v2 1/9] xen/arm: introduce static shared memory
On Fri, 6 May 2022, Penny Zheng wrote:
> From: Penny Zheng <penny.zheng@xxxxxxx>
>
> This patch serie introduces a new feature: setting up static
> shared memory on a dom0less system, through device tree configuration.
>
> This commit parses shared memory node at boot-time, and reserve it in
> bootinfo.reserved_mem to avoid other use.
>
> This commits proposes a new Kconfig CONFIG_STATIC_SHM to wrap
> static-shm-related codes, and this option depends on static memory(
> CONFIG_STATIC_MEMORY). That's because that later we want to reuse a few
> helpers, guarded with CONFIG_STATIC_MEMORY, like acquire_staticmem_pages, etc,
> on static shared memory.
>
> Signed-off-by: Penny Zheng <penny.zheng@xxxxxxx>
Thanks Penny, this version of the series is already so much better than
v1! I have only few minor comments left on the series. One NIT at the
bottom of this file.
> ---
> v2 change:
> - document refinement
> - remove bitmap and use the iteration to check
> - add a new field nr_shm_domain to keep the number of shared domain
> ---
> docs/misc/arm/device-tree/booting.txt | 120 ++++++++++++++++++++++++++
> xen/arch/arm/Kconfig | 6 ++
> xen/arch/arm/bootfdt.c | 68 +++++++++++++++
> xen/arch/arm/include/asm/setup.h | 3 +
> 4 files changed, 197 insertions(+)
>
> diff --git a/docs/misc/arm/device-tree/booting.txt
> b/docs/misc/arm/device-tree/booting.txt
> index a94125394e..e63ce171fc 100644
> --- a/docs/misc/arm/device-tree/booting.txt
> +++ b/docs/misc/arm/device-tree/booting.txt
> @@ -355,3 +355,123 @@ device-tree:
>
> This will reserve a 512MB region starting at the host physical address
> 0x30000000 to be exclusively used by DomU1.
> +
> +Static Shared Memory
> +====================
> +
> +The static shared memory device tree nodes allow users to statically set up
> +shared memory on dom0less system, enabling domains to do shm-based
> +communication.
> +
> +- compatible
> +
> + "xen,domain-shared-memory-v1"
> +
> +- xen,shm-id
> +
> + An u8 value represents the unique identifier of the shared memory region.
> + The maximum identifier shall be "xen,shm-id = <0xff>".
> +
> +- xen,shared-mem
> +
> + An array takes a physical address, which is the base address of the
> + shared memory region in host physical address space, a size, and a guest
> + physical address, as the target address of the mapping. The number of
> cells
> + for the host address (and size) is the same as the guest pseudo-physical
> + address and they are inherited from the parent node.
> +
> +- role (Optional)
> +
> + A string property specifying the ownership of a shared memory region,
> + the value must be one of the following: "owner", or "borrower"
> + A shared memory region could be explicitly backed by one domain, which is
> + called "owner domain", and all the other domains who are also sharing
> + this region are called "borrower domain".
> + If not specified, the default value is "borrower" and owner is
> + "dom_shared", a system domain.
> +
> +As an example:
> +
> +chosen {
> + #address-cells = <0x1>;
> + #size-cells = <0x1>;
> + xen,xen-bootargs = "console=dtuart dtuart=serial0 bootscrub=0";
> +
> + ......
> +
> + /* this is for Dom0 */
> + dom0-shared-mem@10000000 {
> + compatible = "xen,domain-shared-memory-v1";
> + role = "owner";
> + xen,shm-id = <0x0>;
> + xen,shared-mem = <0x10000000 0x10000000 0x10000000>;
> + }
> +
> + domU1 {
> + compatible = "xen,domain";
> + #address-cells = <0x1>;
> + #size-cells = <0x1>;
> + memory = <0 131072>;
> + cpus = <2>;
> + vpl011;
> +
> + /*
> + * shared memory region identified as 0x0(xen,shm-id = <0x0>)
> + * is shared between Dom0 and DomU1.
> + */
> + domU1-shared-mem@10000000 {
> + compatible = "xen,domain-shared-memory-v1";
> + role = "borrower";
> + xen,shm-id = <0x0>;
> + xen,shared-mem = <0x10000000 0x10000000 0x50000000>;
> + }
> +
> + /*
> + * shared memory region identified as 0x1(xen,shm-id = <0x1>)
> + * is shared between DomU1 and DomU2.
> + */
> + domU1-shared-mem@50000000 {
> + compatible = "xen,domain-shared-memory-v1";
> + xen,shm-id = <0x1>;
> + xen,shared-mem = <0x50000000 0x20000000 0x60000000>;
> + }
> +
> + ......
> +
> + };
> +
> + domU2 {
> + compatible = "xen,domain";
> + #address-cells = <0x1>;
> + #size-cells = <0x1>;
> + memory = <0 65536>;
> + cpus = <1>;
> +
> + /*
> + * shared memory region identified as 0x1(xen,shm-id = <0x1>)
> + * is shared between domU1 and domU2.
> + */
> + domU2-shared-mem@50000000 {
> + compatible = "xen,domain-shared-memory-v1";
> + xen,shm-id = <0x1>;
> + xen,shared-mem = <0x50000000 0x20000000 0x70000000>;
> + }
> +
> + ......
> + };
> +};
> +
> +This is an example with two static shared memory regions.
> +
> +For the static shared memory region identified as 0x0, host physical
> +address starting at 0x10000000 of 256MB will be reserved to be shared between
> +Dom0 and DomU1. It will get mapped at 0x10000000 in Dom0 guest physical
> address
> +space, and at 0x50000000 in DomU1 guest physical address space. Dom0 is
> +explicitly defined as the owner domain, and DomU1 is the borrower domain.
> +
> +For the static shared memory region identified as 0x1, host physical
> +address starting at 0x50000000 of 512MB will be reserved to be shared between
> +DomU1 and DomU2. It will get mapped at 0x60000000 in DomU1 guest physical
> +address space, and at 0x70000000 in DomU2 guest physical address space. DomU1
> +and DomU2 are both the borrower domain, the owner domain is the default owner
> +domain dom_shared.
> diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
> index ecfa6822e4..5ee9921f56 100644
> --- a/xen/arch/arm/Kconfig
> +++ b/xen/arch/arm/Kconfig
> @@ -106,6 +106,12 @@ config TEE
>
> source "arch/arm/tee/Kconfig"
>
> +config STATIC_SHM
> + bool "Statically shared memory on a dom0less system" if UNSUPPORTED
> + depends on STATIC_MEMORY
> + help
> + This option enables statically shared memory on a dom0less system.
> +
> endmenu
>
> menu "ARM errata workaround via the alternative framework"
> diff --git a/xen/arch/arm/bootfdt.c b/xen/arch/arm/bootfdt.c
> index e318ef9603..9bd08776a7 100644
> --- a/xen/arch/arm/bootfdt.c
> +++ b/xen/arch/arm/bootfdt.c
> @@ -363,6 +363,70 @@ static int __init process_domain_node(const void *fdt,
> int node,
> size_cells, &bootinfo.reserved_mem, true);
> }
>
> +#ifdef CONFIG_STATIC_SHM
> +static int __init process_shm_node(const void *fdt, int node,
> + u32 address_cells, u32 size_cells)
> +{
> + const struct fdt_property *prop;
> + const __be32 *cell;
> + paddr_t paddr, size;
> + struct meminfo *mem = &bootinfo.reserved_mem;
> + unsigned long i;
> +
> + if ( address_cells < 1 || size_cells < 1 )
> + {
> + printk("fdt: invalid #address-cells or #size-cells for static shared
> memory node.\n");
> + return -EINVAL;
> + }
> +
> + prop = fdt_get_property(fdt, node, "xen,shared-mem", NULL);
> + if ( !prop )
> + return -ENOENT;
> +
> + /*
> + * xen,shared-mem = <paddr, size, gaddr>;
> + * Memory region starting from physical address #paddr of #size shall
> + * be mapped to guest physical address #gaddr as static shared memory
> + * region.
> + */
> + cell = (const __be32 *)prop->data;
> + device_tree_get_reg(&cell, address_cells, size_cells, &paddr, &size);
> + for ( i = 0; i < mem->nr_banks; i++ )
> + {
> + /*
> + * A static shared memory region could be shared between multiple
> + * domains.
> + */
> + if ( paddr == mem->bank[i].start && size == mem->bank[i].size )
> + break;
> + }
> +
> + if ( i == mem->nr_banks )
> + {
> + if ( i < NR_MEM_BANKS )
> + {
> + /* Static shared memory shall be reserved from any other use. */
> + mem->bank[mem->nr_banks].start = paddr;
> + mem->bank[mem->nr_banks].size = size;
> + mem->bank[mem->nr_banks].xen_domain = true;
> + mem->nr_banks++;
> + }
> + else
> + {
> + printk("Warning: Max number of supported memory regions
> reached.\n");
> + return -ENOSPC;
> + }
> + }
> + /*
> + * keep a count of the number of domains, which later may be used to
> + * calculate the number of the reference count.
> + */
> + mem->bank[i].nr_shm_domain++;
> +
> + return 0;
> +}
> +#endif
> +
> static int __init early_scan_node(const void *fdt,
> int node, const char *name, int depth,
> u32 address_cells, u32 size_cells,
> @@ -383,6 +447,10 @@ static int __init early_scan_node(const void *fdt,
> process_chosen_node(fdt, node, name, address_cells, size_cells);
> else if ( depth == 2 && device_tree_node_compatible(fdt, node,
> "xen,domain") )
> rc = process_domain_node(fdt, node, name, address_cells, size_cells);
> +#ifdef CONFIG_STATIC_SHM
> + else if ( depth <= 3 && device_tree_node_compatible(fdt, node,
> "xen,domain-shared-memory-v1") )
> + rc = process_shm_node(fdt, node, address_cells, size_cells);
> +#endif
>
> if ( rc < 0 )
> printk("fdt: node `%s': parsing failed\n", name);
> diff --git a/xen/arch/arm/include/asm/setup.h
> b/xen/arch/arm/include/asm/setup.h
> index 7a1e1d6798..38e02ced36 100644
> --- a/xen/arch/arm/include/asm/setup.h
> +++ b/xen/arch/arm/include/asm/setup.h
> @@ -27,6 +27,9 @@ struct membank {
> paddr_t start;
> paddr_t size;
> bool xen_domain; /* whether the memory bank is bound to a Xen domain. */
> +#ifdef CONFIG_STATIC_SHM
> + unsigned long nr_shm_domain;
> +#endif
This is a NIT but unsigned int would be more than enough. The benefit is
that the following uint8_t end up not needing extra memory on arm64. I
realize this is an overoptimization so it is fine anyway.
Other than this, the patch looks good to me.
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