[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [PATCH v3 1/8] xen/arm: introduce static shared memory



On Thu, 12 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>
> ---
> v3 change:
> - make nr_shm_domain unsigned int
> ---
> 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>".


NIT: a 8-bit integer that represent...

Can be fixed on commit.

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


> +- 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 29671c8df0..c8e8747c3e 100644
> --- a/xen/arch/arm/bootfdt.c
> +++ b/xen/arch/arm/bootfdt.c
> @@ -360,6 +360,70 @@ 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,
> @@ -380,6 +444,10 @@ 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..35449bd7d8 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 int nr_shm_domain;
> +#endif
>  };
>  
>  struct meminfo {
> -- 
> 2.25.1
> 



 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.