Re: [PATCH 5/6] libxl: allow a generation ID to be specified at domain creation

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 03/06/14 14:15, David Vrabel wrote:
> Toolstacks may specify a VM generation ID using the
> u.hvm.generation_id field into libxl_domain_build_info structure, when
> creating a domain.
>
> The toolstack is responsible for providing the correct generation ID
> according to the Microsoft specification (e.g., generating new random
> ones as appropriate when restoring).
>
> Although the specification requires that a ACPI Notify event is raised
> if the generation ID is changed, the generation ID is never changed
> when the domain is in a state to receive such an event (it's either
> newly created or suspended).
>
> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
> ---
>  tools/libxl/Makefile         |    1 +
>  tools/libxl/libxl.h          |    5 +++
>  tools/libxl/libxl_dom.c      |   10 +++++
>  tools/libxl/libxl_internal.h |    4 ++
>  tools/libxl/libxl_types.idl  |    1 +
>  tools/libxl/libxl_vm_genid.c |   89 ++++++++++++++++++++++++++++++++++++++++++
>  6 files changed, 110 insertions(+)
>  create mode 100644 tools/libxl/libxl_vm_genid.c
>
> diff --git a/tools/libxl/Makefile b/tools/libxl/Makefile
> index 4cfa275..5d0e2ec 100644
> --- a/tools/libxl/Makefile
> +++ b/tools/libxl/Makefile
> @@ -77,6 +77,7 @@ LIBXL_OBJS = flexarray.o libxl.o libxl_create.o libxl_dm.o libxl_pci.o \
>  			libxl_json.o libxl_aoutils.o libxl_numa.o \
>  			libxl_save_callout.o _libxl_save_msgs_callout.o \
>  			libxl_qmp.o libxl_event.o libxl_fork.o $(LIBXL_OBJS-y)
> +LIBXL_OBJS += libxl_vm_genid.o
>  LIBXL_OBJS += _libxl_types.o libxl_flask.o _libxl_types_internal.o
>  
>  LIBXL_TESTS += timedereg
> diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
> index 80947c3..9dd57fd 100644
> --- a/tools/libxl/libxl.h
> +++ b/tools/libxl/libxl.h
> @@ -95,6 +95,11 @@
>  #define LIBXL_HAVE_BUILDINFO_EVENT_CHANNELS 1
>  
>  /*
> + * libxl_domain_build_info has the u.hvm.generation_id field.
> + */
> +#define LIBXL_HAVE_BUILDINFO_HVM_GENERATION_ID 1
> +
> +/*
>   * LIBXL_HAVE_DEVICE_DISK_DIRECT_IO_SAFE indicates that a
>   * 'direct_io_safe' field (of boolean type) is present in
>   * libxl_device_disk.
> diff --git a/tools/libxl/libxl_dom.c b/tools/libxl/libxl_dom.c
> index 4804fdf..80bc9ff 100644
> --- a/tools/libxl/libxl_dom.c
> +++ b/tools/libxl/libxl_dom.c
> @@ -314,6 +314,16 @@ int libxl__build_post(libxl__gc *gc, uint32_t domid,
>      if (info->cpuid != NULL)
>          libxl_cpuid_set(ctx, domid, info->cpuid);
>  
> +    if (info->type == LIBXL_DOMAIN_TYPE_HVM 
> +            && !libxl_uuid_is_nil(&info->u.hvm.generation_id)) {
> +        rc = libxl__vm_generation_id_set(CTX, domid,
> +                                         &info->u.hvm.generation_id);
> +        if (rc) {
> +            LOG(ERROR, "Failed to set VM Generation ID");
> +            return rc;
> +        }
> +    }
> +
>      ents = libxl__calloc(gc, 12 + (info->max_vcpus * 2) + 2, sizeof(char *));
>      ents[0] = "memory/static-max";
>      ents[1] = GCSPRINTF("%"PRId64, info->max_memkb);
> diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
> index 457424f..d938b90 100644
> --- a/tools/libxl/libxl_internal.h
> +++ b/tools/libxl/libxl_internal.h
> @@ -3052,6 +3052,10 @@ void libxl__numa_candidate_put_nodemap(libxl__gc *gc,
>      libxl_bitmap_copy(CTX, &cndt->nodemap, nodemap);
>  }
>  
> +_hidden int libxl__vm_generation_id_set(libxl_ctx *ctx, uint32_t domid,
> +                                        const libxl_uuid *uuid);
> +
> +
>  /* Som handy macros for defbool type. */
>  #define LIBXL__DEFBOOL_DEFAULT     (0)
>  #define LIBXL__DEFBOOL_FALSE       (-1)
> diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
> index 52f1aa9..7800509 100644
> --- a/tools/libxl/libxl_types.idl
> +++ b/tools/libxl/libxl_types.idl
> @@ -373,6 +373,7 @@ libxl_domain_build_info = Struct("domain_build_info",[
>                                         ("xen_platform_pci", libxl_defbool),
>                                         ("usbdevice_list",   libxl_string_list),
>                                         ("vendor_device",    libxl_vendor_device),
> +                                       ("generation_id",    libxl_uuid),
>                                         ])),
>                   ("pv", Struct(None, [("kernel", string),
>                                        ("slack_memkb", MemKB),
> diff --git a/tools/libxl/libxl_vm_genid.c b/tools/libxl/libxl_vm_genid.c
> new file mode 100644
> index 0000000..378dcf2
> --- /dev/null
> +++ b/tools/libxl/libxl_vm_genid.c
> @@ -0,0 +1,89 @@
> +/*
> + * Copyright (C) 2014 Citrix Systems R&D Ltd.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU Lesser General Public License as published
> + * by the Free Software Foundation; version 2.1 only. with the special
> + * exception on linking described in file LICENSE.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU Lesser General Public License for more details.
> + */
> +
> +#include "libxl_osdeps.h" /* must come before any other headers */
> +
> +#include "libxl_internal.h"
> +
> +#include <xenctrl.h>
> +#include <xen/hvm/params.h>
> +
> +/*
> + * Set a HVM domain's VM Generation ID.
> + *
> + * For further details, refer to the "Virtual Machine Generation ID"
> + * document from Microsoft.
> + * 
> + *   http://www.microsoft.com/en-us/download/details.aspx?id=30707
> + */
> +int libxl__vm_generation_id_set(libxl_ctx *ctx, uint32_t domid,
> +                                const libxl_uuid *uuid)
> +{
> +    GC_INIT(ctx);
> +    char *dom_path;
> +    char *key;
> +    uint64_t genid[2];
> +    uint64_t paddr = 0;
> +    int rc;
> +
> +    memcpy(genid, libxl_uuid_bytearray((libxl_uuid *)uuid), 16);
> +
> +    /*
> +     * Set the "platform/generation-id" XenStore key to pass the ID to
> +     * hvmloader.
> +     */
> +    dom_path = libxl__xs_get_dompath(gc, domid);
> +    if (!dom_path) {
> +        rc = ERROR_FAIL;
> +        goto out;
> +    }
> +    key = libxl__sprintf(gc, "%s/platform/generation-id", dom_path);
> +    rc = libxl__xs_write(gc, XBT_NULL, key, "%"PRIu64 ":%" PRIu64,
> +                         genid[0], genid[1]);
> +    if (rc < 0)
> +        goto out;
> +
> +    /*
> +     * Update the ID in guest memory (if available).
> +     */
> +    xc_get_hvm_param(ctx->xch, domid, HVM_PARAM_VM_GENERATION_ID_ADDR, &paddr);

This will break 32bit toolstack builds, because xc_get_hvm_param() takes
a pointer to an unsigned long pointer rather than a uint64_t pointer.

It appears that it will also silently truncate the 64bit hvm param to
32bits for a 32bit toolstack...

~Andrew

> +    if (paddr) {
> +        void *vaddr;
> +
> +        vaddr = xc_map_foreign_range(ctx->xch, domid, XC_PAGE_SIZE,
> +                                     PROT_READ | PROT_WRITE,
> +                                     paddr >> XC_PAGE_SHIFT);
> +        if (vaddr == NULL) {
> +            rc = ERROR_FAIL;
> +            goto out;
> +        }
> +        memcpy(vaddr + (paddr & ~XC_PAGE_MASK), genid, 2 * sizeof(*genid));
> +        munmap(vaddr, XC_PAGE_SIZE);
> +
> +        /*
> +         * The spec requries an ACPI Notify event is injected into the
> +         * guest when the generation ID is changed.
> +         *
> +         * This is only called for domains that are suspended or newly
> +         * created and they won't be in a state to receive such an
> +         * event.
> +         */
> +    }
> +
> +    rc = 0;
> +
> +  out:
> +    GC_FREE;
> +    return rc;
> +}