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SubjectRe: [RFC PATCH 12/16] xen/xenbus: support xenbus frontend/backend with xenhost_t
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On 09.05.19 19:25, Ankur Arora wrote:
> As part of xenbus init, both frontend, backend interfaces need to talk
> on the correct xenbus. This might be a local xenstore (backend) or might
> be a XS_PV/XS_HVM interface (frontend) which needs to talk over xenbus
> with the remote xenstored. We bootstrap all of these with evtchn/gfn
> parameters from (*setup_xs)().
>
> Given this we can do appropriate device discovery (in case of frontend)
> and device connectivity for the backend.
> Once done, we stash the xenhost_t * in xen_bus_type, xenbus_device or
> xenbus_watch and then the frontend and backend devices implicitly use
> the correct interface.
>
> The rest of patch is just changing the interfaces where needed.
>
> Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
> ---
> drivers/block/xen-blkback/blkback.c | 10 +-
> drivers/net/xen-netfront.c | 14 +-
> drivers/pci/xen-pcifront.c | 4 +-
> drivers/xen/cpu_hotplug.c | 4 +-
> drivers/xen/manage.c | 28 +--
> drivers/xen/xen-balloon.c | 8 +-
> drivers/xen/xenbus/xenbus.h | 45 ++--
> drivers/xen/xenbus/xenbus_client.c | 32 +--
> drivers/xen/xenbus/xenbus_comms.c | 121 +++++-----
> drivers/xen/xenbus/xenbus_dev_backend.c | 30 ++-
> drivers/xen/xenbus/xenbus_dev_frontend.c | 22 +-
> drivers/xen/xenbus/xenbus_probe.c | 246 +++++++++++++--------
> drivers/xen/xenbus/xenbus_probe_backend.c | 19 +-
> drivers/xen/xenbus/xenbus_probe_frontend.c | 65 +++---
> drivers/xen/xenbus/xenbus_xs.c | 188 +++++++++-------
> include/xen/xen-ops.h | 3 +
> include/xen/xenbus.h | 54 +++--
> include/xen/xenhost.h | 20 ++
> 18 files changed, 536 insertions(+), 377 deletions(-)
>
> diff --git a/drivers/xen/xenbus/xenbus_dev_frontend.c b/drivers/xen/xenbus/xenbus_dev_frontend.c
> index c3e201025ef0..d6e0c397c6a0 100644
> --- a/drivers/xen/xenbus/xenbus_dev_frontend.c
> +++ b/drivers/xen/xenbus/xenbus_dev_frontend.c
> @@ -58,10 +58,14 @@
>
> #include <xen/xenbus.h>
> #include <xen/xen.h>
> +#include <xen/interface/xen.h>
> +#include <xen/xenhost.h>
> #include <asm/xen/hypervisor.h>
>
> #include "xenbus.h"
>
> +static xenhost_t *xh;
> +
> /*
> * An element of a list of outstanding transactions, for which we're
> * still waiting a reply.
> @@ -312,13 +316,13 @@ static void xenbus_file_free(struct kref *kref)
> */
>
> list_for_each_entry_safe(trans, tmp, &u->transactions, list) {
> - xenbus_transaction_end(trans->handle, 1);
> + xenbus_transaction_end(xh, trans->handle, 1);
> list_del(&trans->list);
> kfree(trans);
> }
>
> list_for_each_entry_safe(watch, tmp_watch, &u->watches, list) {
> - unregister_xenbus_watch(&watch->watch);
> + unregister_xenbus_watch(xh, &watch->watch);
> list_del(&watch->list);
> free_watch_adapter(watch);
> }
> @@ -450,7 +454,7 @@ static int xenbus_write_transaction(unsigned msg_type,
> (!strcmp(msg->body, "T") || !strcmp(msg->body, "F"))))
> return xenbus_command_reply(u, XS_ERROR, "EINVAL");
>
> - rc = xenbus_dev_request_and_reply(&msg->hdr, u);
> + rc = xenbus_dev_request_and_reply(xh, &msg->hdr, u);
> if (rc && trans) {
> list_del(&trans->list);
> kfree(trans);
> @@ -489,7 +493,7 @@ static int xenbus_write_watch(unsigned msg_type, struct xenbus_file_priv *u)
> watch->watch.callback = watch_fired;
> watch->dev_data = u;
>
> - err = register_xenbus_watch(&watch->watch);
> + err = register_xenbus_watch(xh, &watch->watch);
> if (err) {
> free_watch_adapter(watch);
> rc = err;
> @@ -500,7 +504,7 @@ static int xenbus_write_watch(unsigned msg_type, struct xenbus_file_priv *u)
> list_for_each_entry(watch, &u->watches, list) {
> if (!strcmp(watch->token, token) &&
> !strcmp(watch->watch.node, path)) {
> - unregister_xenbus_watch(&watch->watch);
> + unregister_xenbus_watch(xh, &watch->watch);
> list_del(&watch->list);
> free_watch_adapter(watch);
> break;
> @@ -618,8 +622,9 @@ static ssize_t xenbus_file_write(struct file *filp,
> static int xenbus_file_open(struct inode *inode, struct file *filp)
> {
> struct xenbus_file_priv *u;
> + struct xenstore_private *xs = xs_priv(xh);
>
> - if (xen_store_evtchn == 0)
> + if (xs->store_evtchn == 0)
> return -ENOENT;
>
> nonseekable_open(inode, filp);
> @@ -687,6 +692,11 @@ static int __init xenbus_init(void)
> if (!xen_domain())
> return -ENODEV;
>
> + if (xen_driver_domain() && xen_nested())
> + xh = xh_remote;
> + else
> + xh = xh_default;

This precludes any mixed use of L0 and L1 frontends. With this move you
make it impossible to e.g. use a driver domain for networking in L1 with
a L1-local PV disk, or pygrub in L1 dom0.


Juergen

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