Re: add ivshmem property master

[Martin Kletzander <mkletzan@xxxxxxxxxx>]

[Please use git send-email or a normal client, this attachment is difficult to
go through, not to mention that the diff is completely broken]

On Fri, Feb 01, 2019 at 08:16:20AM +0000, 吴 雨霖 wrote:
> [Problem Description]
>
>  I read qemu-doc.texi in qemu-mster source code, which have a explain of migrating ivshmem below
>
> “With device property @option{master=on}, the guest will copy the shared.memory on migration to the destination host.  With @option{master=off}, the guest will not be able to migrate with the device attached.”
>
>  However, libvirt library can not recognize the property “master=on”. When I directly used command "qemu-kvm -device ivshmem-plain,id=shmem0,memdev=shmmem-shmem0,master=on,bus=pci.0,addr=0xa” to launch a guest, qemu support ivshmem property master=on.
>
>  So, I suggest adding code to support property master=on in libvirt.

QEMU supports that, but libvirt doesn't.  I remember there was a reason
for it, but I can't seem to recall what the particular reason was.

What is the reason for you to need master=on?

> [Code Review]
>
>
>
>    The below is the part of source code in qemu-master. There's no definition here  about ivshmem master.
>
> domain_conf.h
>
> struct _virDomainShmemDef {
>
>    char *name;
>
>    unsigned long long size;
>
>    int model; /* enum virDomainShmemModel */
>
>    struct {
>
>        bool enabled;
>
>        virDomainChrSourceDef chr;
>
>    } server;
>
>    struct {
>
>        bool enabled;
>
>        unsigned vectors;
>
>        virTristateSwitch ioeventfd;
>
>    } msi;
>
>    virDomainDeviceInfo info;
>
> };
>
> [changed code]
>
> src/conf/domain_conf.c
>
> src/conf/domain_conf.h
>
>
>
> [Detail of Source Code Modification]
>
>
> diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
> index 9f75dc4..b41be37 100644
> --- a/src/conf/domain_conf.c
> +++ b/src/conf/domain_conf.c
> @@ -14665,7 +14665,6 @@ virDomainShmemDefParseXML(virDomainXMLOptionPtr xmlopt,
>     xmlNodePtr save = ctxt->node;
>     xmlNodePtr server = NULL;
>
> -
>     if (VIR_ALLOC(def) < 0)
>         return NULL;
>
> -
>     if (VIR_ALLOC(def) < 0)
>         return NULL;
>
> @@ -14685,12 +14684,28 @@ virDomainShmemDefParseXML(virDomainXMLOptionPtr xmlopt,
>         VIR_FREE(tmp);
>     }
>
> +
>     if (!(def->name = virXMLPropString(node, "name"))) {
>         virReportError(VIR_ERR_XML_ERROR, "%s",
>                        _("shmem element must contain 'name' attribute"));
>         goto cleanup;
>     }
>
> +
> +       if ((tmp = virXMLPropString(node, "master"))) {
> +               int val;
> +
> +               if ((val = virTristateSwitchTypeFromString(tmp)) <= 0) {
> +                       virReportError(VIR_ERR_XML_ERROR,
> +                                                  _("invalid ivshmem master setting for shmem: '%s'"),
> +                                                  tmp);
> +                       goto cleanup;
> +               }
> +               def->master = val;
> +               VIR_FREE(tmp);
> +       }
> +
> +
>     if (virDomainParseScaledValue("./size[1]", NULL, ctxt,
>                                   &def->size, 1, ULLONG_MAX, false) < 0)
>         goto cleanup;
> diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
> index f1e6e4e..615d721 100644
> --- a/src/conf/domain_conf.h
> +++ b/src/conf/domain_conf.h
> @@ -1727,8 +1727,10 @@ typedef enum {
>
> struct _virDomainShmemDef {
>     char *name;
> +
>     unsigned long long size;
>     int model; /* enum virDomainShmemModel */
> +   virTristateSwitch master;
>     struct {
>         bool enabled;
>         virDomainChrSourceDef chr;
> }

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