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Re: [Qemu-devel] [PATCH v3 2/3] xen: write information about supported b
From: |
Juergen Gross |
Subject: |
Re: [Qemu-devel] [PATCH v3 2/3] xen: write information about supported backends |
Date: |
Wed, 11 May 2016 10:36:28 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.7.0 |
On 10/05/16 18:21, Anthony PERARD wrote:
> On Fri, May 06, 2016 at 11:42:45AM +0200, Juergen Gross wrote:
>> Add a Xenstore directory for each supported pv backend. This will allow
>> Xen tools to decide which backend type to use in case there are
>> multiple possibilities.
>>
>> The information is added under
>> /local/domain/<backend-domid>/device-model/<domid>/backends
>> before the "running" state is written to Xenstore. Using a directory
>> for each backend enables us to add parameters for specific backends
>> in the future.
>>
>> This interface is documented in the Xen source repository in the file
>> docs/misc/qemu-backends.txt
>>
>> In order to reuse the Xenstore directory creation already present in
>> hw/xen/xen_devconfig.c move the related functions to
>> hw/xen/xen_backend.c where they fit better.
>>
>> Signed-off-by: Juergen Gross <address@hidden>
>> ---
>> V3: Added .backend_register function to XenDevOps in order to have a
>> way to let the backend decide whether all prerequisites are met
>> for support.
>>
>> V2: update commit message as requested by Stefano
>> ---
>> hw/xen/xen_backend.c | 60
>> ++++++++++++++++++++++++++++++++++++++++++++
>> hw/xen/xen_devconfig.c | 52 ++------------------------------------
>> include/hw/xen/xen_backend.h | 2 ++
>> 3 files changed, 64 insertions(+), 50 deletions(-)
>>
>> diff --git a/hw/xen/xen_backend.c b/hw/xen/xen_backend.c
>> index 60575ad..6d8b3a5 100644
>> --- a/hw/xen/xen_backend.c
>> +++ b/hw/xen/xen_backend.c
>> @@ -726,6 +772,20 @@ err:
>>
>> int xen_be_register(const char *type, struct XenDevOps *ops)
>> {
>> + char path[50];
>> + int rc;
>> +
>> + if (ops->backend_register) {
>> + rc = ops->backend_register();
>> + if (rc) {
>> + return rc;
>> + }
>> + }
>> +
>> + snprintf(path, sizeof (path), "device-model/%u/backends/%s", xen_domid,
>> + type);
>> + xenstore_mkdir(path, XS_PERM_READ);
>
> Do you actually need the guest to be able to read those paths?
No, you are right.
>> diff --git a/hw/xen/xen_devconfig.c b/hw/xen/xen_devconfig.c
>> index 1f30fe4..b7d290d 100644
>> --- a/hw/xen/xen_devconfig.c
>> +++ b/hw/xen/xen_devconfig.c
>> @@ -5,54 +5,6 @@
>>
>> /* ------------------------------------------------------------- */
>>
>> -struct xs_dirs {
>> - char *xs_dir;
>> - QTAILQ_ENTRY(xs_dirs) list;
>> -};
>> -static QTAILQ_HEAD(xs_dirs_head, xs_dirs) xs_cleanup =
>> QTAILQ_HEAD_INITIALIZER(xs_cleanup);
>> -
>> -static void xen_config_cleanup_dir(char *dir)
>> -{
>> - struct xs_dirs *d;
>> -
>> - d = g_malloc(sizeof(*d));
>> - d->xs_dir = dir;
>> - QTAILQ_INSERT_TAIL(&xs_cleanup, d, list);
>> -}
>> -
>> -void xen_config_cleanup(void)
>> -{
>> - struct xs_dirs *d;
>> -
>> - QTAILQ_FOREACH(d, &xs_cleanup, list) {
>> - xs_rm(xenstore, 0, d->xs_dir);
>> - }
>> -}
>> -
>> -/* ------------------------------------------------------------- */
>> -
>> -static int xen_config_dev_mkdir(char *dev, int p)
>> -{
>> - struct xs_permissions perms[2] = {{
>> - .id = 0, /* set owner: dom0 */
>> - },{
>> - .id = xen_domid,
>> - .perms = p,
>> - }};
>> -
>
> The function looks like it as been tailored to mkdir for config of
> backends. So it does not seems out of place.
It has been tailored for config of _devices_ by the backend.
I still think it would fit better now into xen_backend.c, OTOH in case
you like it better in xen_devconfig.c I won't argue against it.
Juergen