[PATCH v2 0/9] Enable Xenstore-stubdom Live Update

[PATCH v2 0/9] Enable Xenstore-stubdom Live Update

[Juergen Gross]

With this series applied I was able to perform Live Update of Xenstore
running in a PVH stubdom.

One relevant change in this series is how the Xenstore state is being
read after activating the new binary. Instead of using mmap() the
state records are read one by one via fread(). This might have a
small performance impact for the daemon live update case, but it
should be neglectable.

Changes in V2:
- rebase
- former patches 1 and 2 have been committed already
- former patch 5 moved to start of the series (has all needed Acks)
- new patches 8 and 9

Juergen Gross (9):
  xenstored: use fread() instead of mmap() for reading live update state
  libevtchn: add O_CLOEXEC support for Mini-OS
  libxengnttab: set the cloexec flag on Mini-OS
  xenstored: don't use xenevtchn_fdopen() in stubdom
  tools/libxenevtchn: add xenevtchn_bind() under Mini-OS
  xenstored: rebind event channels after live update in stubdom
  tools/xenstored: make stubdom_init() live update aware
  SUPPORT.md: add xenstorepvh-stubdom live update
  CHANGELOG.md: add xenstorepvh-stubdom live update

 CHANGELOG.md               |  1 +
 SUPPORT.md                 |  2 +-
 tools/include/xenevtchn.h  | 11 +++++
 tools/libs/evtchn/minios.c | 23 +++++++--
 tools/libs/gnttab/minios.c |  1 +
 tools/xenstored/core.c     |  5 +-
 tools/xenstored/core.h     |  8 +++-
 tools/xenstored/domain.c   | 25 ++++++----
 tools/xenstored/domain.h   |  2 +-
 tools/xenstored/lu.c       | 95 +++++++++++++++++++++++---------------
 tools/xenstored/minios.c   | 22 +++++++--
 tools/xenstored/posix.c    | 10 ++++
 12 files changed, 147 insertions(+), 58 deletions(-)

-- 
2.43.0

[PATCH v2 1/9] xenstored: use fread() instead of mmap() for reading live update state

[Juergen Gross]

Mini-OS doesn't support using mmap() for accessing a file. In order
to support reading the live update state from a 9pfs based file, use
fread() instead of mmap().

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>
---
V2:
- move to start of series
---
 tools/xenstored/lu.c | 95 +++++++++++++++++++++++++++-----------------
 1 file changed, 59 insertions(+), 36 deletions(-)

diff --git a/tools/xenstored/lu.c b/tools/xenstored/lu.c
index 77e0d377c5..f2c8b92d07 100644
--- a/tools/xenstored/lu.c
+++ b/tools/xenstored/lu.c
@@ -27,9 +27,11 @@ struct live_update *lu_status;
 
 struct lu_dump_state {
 	void *buf;
+	unsigned int buf_size;
 	unsigned int size;
-	int fd;
+	unsigned int offset;
 	char *filename;
+	FILE *fp;
 };
 
 static int lu_destroy(void *data)
@@ -80,9 +82,10 @@ bool lu_is_pending(void)
 	return lu_status != NULL;
 }
 
-static void lu_get_dump_state(struct lu_dump_state *state)
+static void lu_get_dump_state(void *ctx, struct lu_dump_state *state)
 {
 	struct stat statbuf;
+	int fd;
 
 	state->size = 0;
 
@@ -91,82 +94,107 @@ static void lu_get_dump_state(struct lu_dump_state *state)
 	if (!state->filename)
 		barf("Allocation failure");
 
-	state->fd = open(state->filename, O_RDONLY);
-	if (state->fd < 0)
-		return;
-	if (fstat(state->fd, &statbuf) != 0)
-		goto out_close;
+	fd = open(state->filename, O_RDONLY);
+	if (fd < 0)
+		barf("No state file found");
+	if (fstat(fd, &statbuf) != 0)
+		barf("Could not fstat state file");
 	state->size = statbuf.st_size;
 
-	state->buf = mmap(NULL, state->size, PROT_READ, MAP_PRIVATE,
-			  state->fd, 0);
-	if (state->buf == MAP_FAILED) {
-		state->size = 0;
-		goto out_close;
-	}
+	/* Start with a 4k buffer. If needed we'll reallocate a larger one. */
+	state->buf_size = 4096;
+	state->buf = talloc_size(ctx, state->buf_size);
+	if (!state->buf)
+		barf("Allocation failure");
 
-	return;
+	state->fp = fdopen(fd, "r");
+}
 
- out_close:
-	close(state->fd);
+static void lu_dump_close(FILE *fp)
+{
+	fclose(fp);
 }
 
 static void lu_close_dump_state(struct lu_dump_state *state)
 {
 	assert(state->filename != NULL);
 
-	munmap(state->buf, state->size);
-	close(state->fd);
+	lu_dump_close(state->fp);
 
 	unlink(state->filename);
 	talloc_free(state->filename);
+	talloc_free(state->buf);
+}
+
+static void lu_read_data(void *ctx, struct lu_dump_state *state,
+			 unsigned int size)
+{
+	if (state->offset + size > state->size)
+		barf("Inconsistent state data");
+
+	if (size > state->buf_size) {
+		state->buf = talloc_realloc_size(ctx, state->buf, size);
+		if (!state->buf)
+			barf("Allocation failure");
+		state->buf_size = size;
+	}
+
+	if (fread(state->buf, size, 1, state->fp) != 1)
+		barf("State read error");
+
+	state->offset += size;
 }
 
 void lu_read_state(void)
 {
 	struct lu_dump_state state = {};
-	struct xs_state_record_header *head;
+	struct xs_state_record_header head;
 	void *ctx = talloc_new(NULL); /* Work context for subfunctions. */
 	struct xs_state_preamble *pre;
 	unsigned int version;
 
 	syslog(LOG_INFO, "live-update: read state\n");
-	lu_get_dump_state(&state);
+	lu_get_dump_state(ctx, &state);
 	if (state.size == 0)
 		barf_perror("No state found after live-update");
 
+	lu_read_data(ctx, &state, sizeof(*pre));
 	pre = state.buf;
 	version = be32toh(pre->version);
 	if (memcmp(pre->ident, XS_STATE_IDENT, sizeof(pre->ident)) ||
 	    !version || version > XS_STATE_VERSION ||
 	    pre->flags != XS_STATE_FLAGS)
 		barf("Unknown record identifier");
-	for (head = state.buf + sizeof(*pre);
-	     head->type != XS_STATE_TYPE_END &&
-		(void *)head - state.buf < state.size;
-	     head = (void *)head + sizeof(*head) + head->length) {
-		switch (head->type) {
+
+	for (;;) {
+		lu_read_data(ctx, &state, sizeof(head));
+		head = *(struct xs_state_record_header *)(state.buf);
+		if (head.type == XS_STATE_TYPE_END)
+			break;
+		lu_read_data(ctx, &state, head.length);
+
+		switch (head.type) {
 		case XS_STATE_TYPE_GLOBAL:
-			read_state_global(ctx, head + 1);
+			read_state_global(ctx, state.buf);
 			break;
 		case XS_STATE_TYPE_CONN:
-			read_state_connection(ctx, head + 1);
+			read_state_connection(ctx, state.buf);
 			break;
 		case XS_STATE_TYPE_WATCH:
-			read_state_watch(ctx, head + 1);
+			read_state_watch(ctx, state.buf);
 			break;
 		case XS_STATE_TYPE_TA:
 			xprintf("live-update: ignore transaction record\n");
 			break;
 		case XS_STATE_TYPE_NODE:
-			read_state_node(ctx, head + 1);
+			read_state_node(ctx, state.buf);
 			break;
 		case XS_STATE_TYPE_DOMAIN:
-			read_state_domain(ctx, head + 1, version);
+			read_state_domain(ctx, state.buf, version);
 			break;
 		default:
 			xprintf("live-update: unknown state record %08x\n",
-				head->type);
+				head.type);
 			break;
 		}
 	}
@@ -271,11 +299,6 @@ static FILE *lu_dump_open(const void *ctx)
 	return fdopen(fd, "w");
 }
 
-static void lu_dump_close(FILE *fp)
-{
-	fclose(fp);
-}
-
 static const char *lu_dump_state(const void *ctx, struct connection *conn)
 {
 	FILE *fp;
-- 
2.43.0

Re: [PATCH v2 1/9] xenstored: use fread() instead of mmap() for reading live update state

[Andrew Cooper]

On 29/07/2025 12:01 pm, Juergen Gross wrote:
> diff --git a/tools/xenstored/lu.c b/tools/xenstored/lu.c
> index 77e0d377c5..f2c8b92d07 100644
> --- a/tools/xenstored/lu.c
> +++ b/tools/xenstored/lu.c
> @@ -27,9 +27,11 @@ struct live_update *lu_status;
>  
>  struct lu_dump_state {
>  	void *buf;
> +	unsigned int buf_size;
>  	unsigned int size;
> -	int fd;
> +	unsigned int offset;
>  	char *filename;
> +	FILE *fp;

I know there's already one unsigned int size here, but life is too short
to not use size_t from the get-go.

~Andrew

Re: [PATCH v2 1/9] xenstored: use fread() instead of mmap() for reading live update state

[Andrew Cooper]

On 29/07/2025 8:21 pm, Andrew Cooper wrote:
> On 29/07/2025 12:01 pm, Juergen Gross wrote:
>> diff --git a/tools/xenstored/lu.c b/tools/xenstored/lu.c
>> index 77e0d377c5..f2c8b92d07 100644
>> --- a/tools/xenstored/lu.c
>> +++ b/tools/xenstored/lu.c
>> @@ -27,9 +27,11 @@ struct live_update *lu_status;
>>  
>>  struct lu_dump_state {
>>  	void *buf;
>> +	unsigned int buf_size;
>>  	unsigned int size;
>> -	int fd;
>> +	unsigned int offset;
>>  	char *filename;
>> +	FILE *fp;
> I know there's already one unsigned int size here, but life is too short
> to not use size_t from the get-go.

That said, offset really needs to be an offs64_t if you want 32bit
guests to 9P safely on a modern filesystem.

~Andrew

Re: [PATCH v2 1/9] xenstored: use fread() instead of mmap() for reading live update state

[Jürgen Groß]

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On 29.07.25 21:25, Andrew Cooper wrote:
> On 29/07/2025 8:21 pm, Andrew Cooper wrote:
>> On 29/07/2025 12:01 pm, Juergen Gross wrote:
>>> diff --git a/tools/xenstored/lu.c b/tools/xenstored/lu.c
>>> index 77e0d377c5..f2c8b92d07 100644
>>> --- a/tools/xenstored/lu.c
>>> +++ b/tools/xenstored/lu.c
>>> @@ -27,9 +27,11 @@ struct live_update *lu_status;
>>>   
>>>   struct lu_dump_state {
>>>   	void *buf;
>>> +	unsigned int buf_size;
>>>   	unsigned int size;
>>> -	int fd;
>>> +	unsigned int offset;
>>>   	char *filename;
>>> +	FILE *fp;
>> I know there's already one unsigned int size here, but life is too short
>> to not use size_t from the get-go.
> 
> That said, offset really needs to be an offs64_t if you want 32bit
> guests to 9P safely on a modern filesystem.

For 32bit guests I don't see a problem here, as this would mean the Xenstore
state would exceed 4GB, which seems unlikely using an in-memory data base in
a system supporting less than 2GB of memory (the Mini-OS limit for 32bit is
1GB, while a 32bit daemon can use max. 2GB of virtual memory).

Using unsigned int is a potential problem in 64bit mode, though. So switching
to size_t for size and off64_t for offset seems sensible.


Juergen

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Re: [PATCH v2 1/9] xenstored: use fread() instead of mmap() for reading live update state

[Juergen Gross]

[-- Attachment #1.1.1: Type: text/plain, Size: 1459 bytes --]

On 30.07.25 08:18, Jürgen Groß wrote:
> On 29.07.25 21:25, Andrew Cooper wrote:
>> On 29/07/2025 8:21 pm, Andrew Cooper wrote:
>>> On 29/07/2025 12:01 pm, Juergen Gross wrote:
>>>> diff --git a/tools/xenstored/lu.c b/tools/xenstored/lu.c
>>>> index 77e0d377c5..f2c8b92d07 100644
>>>> --- a/tools/xenstored/lu.c
>>>> +++ b/tools/xenstored/lu.c
>>>> @@ -27,9 +27,11 @@ struct live_update *lu_status;
>>>>   struct lu_dump_state {
>>>>       void *buf;
>>>> +    unsigned int buf_size;
>>>>       unsigned int size;
>>>> -    int fd;
>>>> +    unsigned int offset;
>>>>       char *filename;
>>>> +    FILE *fp;
>>> I know there's already one unsigned int size here, but life is too short
>>> to not use size_t from the get-go.
>>
>> That said, offset really needs to be an offs64_t if you want 32bit
>> guests to 9P safely on a modern filesystem.
> 
> For 32bit guests I don't see a problem here, as this would mean the Xenstore
> state would exceed 4GB, which seems unlikely using an in-memory data base in
> a system supporting less than 2GB of memory (the Mini-OS limit for 32bit is
> 1GB, while a 32bit daemon can use max. 2GB of virtual memory).
> 
> Using unsigned int is a potential problem in 64bit mode, though. So switching
> to size_t for size and off64_t for offset seems sensible.

Meh, off64_t seems to be unknown in Mini-OS environment. Will use size_t for
offset, too.


Juergen

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[PATCH v2 2/9] libevtchn: add O_CLOEXEC support for Mini-OS

[Juergen Gross]

With Mini-OS now supporting O_CLOEXEC for the kexec case, no longer
ignore the XENEVTCHN_NO_CLOEXEC flag in minios.c.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>
---
 tools/libs/evtchn/minios.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/tools/libs/evtchn/minios.c b/tools/libs/evtchn/minios.c
index 046cd28d37..0d2a201438 100644
--- a/tools/libs/evtchn/minios.c
+++ b/tools/libs/evtchn/minios.c
@@ -114,10 +114,6 @@ static void evtchn_initialize(void)
     ftype_evtchn = alloc_file_type(&evtchn_ops);
 }
 
-/*
- * XENEVTCHN_NO_CLOEXEC is being ignored, as there is no exec() call supported
- * in Mini-OS.
- */
 int osdep_evtchn_open(xenevtchn_handle *xce, unsigned int flags)
 {
     int fd;
@@ -137,6 +133,8 @@ int osdep_evtchn_open(xenevtchn_handle *xce, unsigned int flags)
         return -1;
     }
 
+    if ( !(flags & XENEVTCHN_NO_CLOEXEC) )
+        file->cloexec = true;
     file->dev = ports;
     XEN_LIST_INIT(&ports->list);
     xce->fd = fd;
-- 
2.43.0

Re: [PATCH v2 2/9] libevtchn: add O_CLOEXEC support for Mini-OS

[Anthony PERARD]

On Tue, Jul 29, 2025 at 01:01:38PM +0200, Juergen Gross wrote:
> With Mini-OS now supporting O_CLOEXEC for the kexec case, no longer
> ignore the XENEVTCHN_NO_CLOEXEC flag in minios.c.
> 
> Signed-off-by: Juergen Gross <jgross@suse.com>
> Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>

Acked-by: Anthony PERARD <anthony.perard@vates.tech>

Thanks,

-- 
Anthony PERARD

[PATCH v2 3/9] libxengnttab: set the cloexec flag on Mini-OS

[Juergen Gross]

With Mini-OS now supporting the O_CLOEXEC flag for the kexec case,
set the related cloexec flag in minios.c.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>
---
 tools/libs/gnttab/minios.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/libs/gnttab/minios.c b/tools/libs/gnttab/minios.c
index cac89f0ba6..63bbdc7719 100644
--- a/tools/libs/gnttab/minios.c
+++ b/tools/libs/gnttab/minios.c
@@ -74,6 +74,7 @@ int osdep_gnttab_open(xengnttab_handle *xgt)
     }
 
     file->dev = gntmap;
+    file->cloexec = true;
     gntmap_init(gntmap);
     xgt->fd = fd;
     return 0;
-- 
2.43.0

Re: [PATCH v2 3/9] libxengnttab: set the cloexec flag on Mini-OS

[Anthony PERARD]

On Tue, Jul 29, 2025 at 01:01:39PM +0200, Juergen Gross wrote:
> With Mini-OS now supporting the O_CLOEXEC flag for the kexec case,
> set the related cloexec flag in minios.c.
> 
> Signed-off-by: Juergen Gross <jgross@suse.com>
> Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>

Acked-by: Anthony PERARD <anthony.perard@vates.tech>

Thanks,

-- 
Anthony PERARD

[PATCH v2 4/9] xenstored: don't use xenevtchn_fdopen() in stubdom

[Juergen Gross]

When running in a stubdom environment xenevtchn_fdopen() won't work,
as any file descriptor state is lost across kexec().

Use a wrapper to replace the call of xenevtchn_fdopen() with the
really needed xenevtchn_open() when running on top of Mini-OS.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>
---
 tools/xenstored/core.h   | 3 +++
 tools/xenstored/domain.c | 2 +-
 tools/xenstored/minios.c | 5 +++++
 tools/xenstored/posix.c  | 5 +++++
 4 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/tools/xenstored/core.h b/tools/xenstored/core.h
index 1ba9592d16..bef24a688c 100644
--- a/tools/xenstored/core.h
+++ b/tools/xenstored/core.h
@@ -29,6 +29,7 @@
 #include <stdint.h>
 #include <time.h>
 #include <errno.h>
+#include <xenevtchn.h>
 
 #include "xenstore_lib.h"
 #include "xenstore_state.h"
@@ -405,6 +406,8 @@ void handle_special_fds(void);
 int get_socket_fd(void);
 void set_socket_fd(int fd);
 
+xenevtchn_handle *evtchn_fdopen(int fd);
+
 #ifdef __MINIOS__
 void mount_9pfs(void);
 #endif
diff --git a/tools/xenstored/domain.c b/tools/xenstored/domain.c
index 2362216a7a..6767d29a19 100644
--- a/tools/xenstored/domain.c
+++ b/tools/xenstored/domain.c
@@ -1396,7 +1396,7 @@ void domain_init(int evtfd)
 	if (evtfd < 0)
 		xce_handle = xenevtchn_open(NULL, XENEVTCHN_NO_CLOEXEC);
 	else
-		xce_handle = xenevtchn_fdopen(NULL, evtfd, 0);
+		xce_handle = evtchn_fdopen(evtfd);
 
 	if (xce_handle == NULL)
 		barf_perror("Failed to open evtchn device");
diff --git a/tools/xenstored/minios.c b/tools/xenstored/minios.c
index a229954cf4..aa1f03fd6b 100644
--- a/tools/xenstored/minios.c
+++ b/tools/xenstored/minios.c
@@ -85,6 +85,11 @@ void set_socket_fd(int fd)
 {
 }
 
+xenevtchn_handle *evtchn_fdopen(int fd)
+{
+	return xenevtchn_open(NULL, XENEVTCHN_NO_CLOEXEC);
+}
+
 static void mount_thread(void *p)
 {
 	xenbus_event_queue events = NULL;
diff --git a/tools/xenstored/posix.c b/tools/xenstored/posix.c
index 6037d739d0..ebdec82215 100644
--- a/tools/xenstored/posix.c
+++ b/tools/xenstored/posix.c
@@ -408,6 +408,11 @@ void set_socket_fd(int fd)
 	sock = fd;
 }
 
+xenevtchn_handle *evtchn_fdopen(int fd)
+{
+	return xenevtchn_fdopen(NULL, fd, 0);
+}
+
 const char *xenstore_rundir(void)
 {
 	return xenstore_daemon_rundir();
-- 
2.43.0

[PATCH v2 5/9] tools/libxenevtchn: add xenevtchn_bind() under Mini-OS

[Juergen Gross]

In order to reactivate an event channel after kexec() of Mini-OS,
libxenevtchn needs to allocate the port data for the event channel
and set the handler again. Add a new interface xenevtchn_bind()
for that purpose, available under Mini-OS only.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>
---
 tools/include/xenevtchn.h  | 11 +++++++++++
 tools/libs/evtchn/minios.c | 17 +++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/tools/include/xenevtchn.h b/tools/include/xenevtchn.h
index 1255c85178..113a718d67 100644
--- a/tools/include/xenevtchn.h
+++ b/tools/include/xenevtchn.h
@@ -173,6 +173,17 @@ int xenevtchn_unmask(xenevtchn_handle *xce, evtchn_port_t port);
  */
 int xenevtchn_restrict(xenevtchn_handle *xce, domid_t domid);
 
+/**
+ * Bind an event channel under Mini-OS.
+ *
+ * Bind an event channel specified by its known port after a kexec() of
+ * Mini-OS. This function is available under Mini-OS only!
+ *
+ * @parm xce handle to the open evtchn interface
+ * @parm port the event channel to bind again
+ * @return 0 on success, -1 on failure with errno set appropriately.
+ */
+int xenevtchn_bind(xenevtchn_handle *xce, evtchn_port_t port);
 #endif
 
 /*
diff --git a/tools/libs/evtchn/minios.c b/tools/libs/evtchn/minios.c
index 0d2a201438..36e4201249 100644
--- a/tools/libs/evtchn/minios.c
+++ b/tools/libs/evtchn/minios.c
@@ -259,6 +259,23 @@ xenevtchn_port_or_error_t xenevtchn_bind_interdomain(xenevtchn_handle *xce,
     return local_port;
 }
 
+int xenevtchn_bind(xenevtchn_handle *xce, evtchn_port_t port)
+{
+    struct port_info *port_info;
+    port_info = port_alloc(xce);
+    if ( port_info == NULL )
+        return -1;
+
+    printf("xenevtchn_bind(%"PRId32")\n", port);
+    bind_evtchn(port, evtchn_handler, xce);
+
+    port_info->bound = true;
+    port_info->port = port;
+    unmask_evtchn(port);
+
+    return 0;
+}
+
 int xenevtchn_unbind(xenevtchn_handle *xce, evtchn_port_t port)
 {
     int fd = xce->fd;
-- 
2.43.0

Re: [PATCH v2 5/9] tools/libxenevtchn: add xenevtchn_bind() under Mini-OS

[Anthony PERARD]

On Tue, Jul 29, 2025 at 01:01:41PM +0200, Juergen Gross wrote:
> In order to reactivate an event channel after kexec() of Mini-OS,
> libxenevtchn needs to allocate the port data for the event channel
> and set the handler again. Add a new interface xenevtchn_bind()
> for that purpose, available under Mini-OS only.
> 
> Signed-off-by: Juergen Gross <jgross@suse.com>
> Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>
> ---
>  tools/include/xenevtchn.h  | 11 +++++++++++
>  tools/libs/evtchn/minios.c | 17 +++++++++++++++++
>  2 files changed, 28 insertions(+)
> 
> diff --git a/tools/include/xenevtchn.h b/tools/include/xenevtchn.h
> index 1255c85178..113a718d67 100644
> --- a/tools/include/xenevtchn.h
> +++ b/tools/include/xenevtchn.h
> @@ -173,6 +173,17 @@ int xenevtchn_unmask(xenevtchn_handle *xce, evtchn_port_t port);
>   */
>  int xenevtchn_restrict(xenevtchn_handle *xce, domid_t domid);
>  
> +/**
> + * Bind an event channel under Mini-OS.
> + *
> + * Bind an event channel specified by its known port after a kexec() of
> + * Mini-OS. This function is available under Mini-OS only!

Would guarding this prototype within "#ifdef __MINIOS__" be useful to
prevent it from been used? That would give an error earlier when
compiling, rather than later when linking a binary.

In anycase: Acked-by: Anthony PERARD <anthony.perard@vates.tech>

> + *
> + * @parm xce handle to the open evtchn interface
> + * @parm port the event channel to bind again
> + * @return 0 on success, -1 on failure with errno set appropriately.
> + */
> +int xenevtchn_bind(xenevtchn_handle *xce, evtchn_port_t port);
>  #endif
>  
>  /*

Thanks,

-- 
Anthony PERARD

Re: [PATCH v2 5/9] tools/libxenevtchn: add xenevtchn_bind() under Mini-OS

[Jürgen Groß]

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On 29.07.25 19:00, Anthony PERARD wrote:
> On Tue, Jul 29, 2025 at 01:01:41PM +0200, Juergen Gross wrote:
>> In order to reactivate an event channel after kexec() of Mini-OS,
>> libxenevtchn needs to allocate the port data for the event channel
>> and set the handler again. Add a new interface xenevtchn_bind()
>> for that purpose, available under Mini-OS only.
>>
>> Signed-off-by: Juergen Gross <jgross@suse.com>
>> Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>
>> ---
>>   tools/include/xenevtchn.h  | 11 +++++++++++
>>   tools/libs/evtchn/minios.c | 17 +++++++++++++++++
>>   2 files changed, 28 insertions(+)
>>
>> diff --git a/tools/include/xenevtchn.h b/tools/include/xenevtchn.h
>> index 1255c85178..113a718d67 100644
>> --- a/tools/include/xenevtchn.h
>> +++ b/tools/include/xenevtchn.h
>> @@ -173,6 +173,17 @@ int xenevtchn_unmask(xenevtchn_handle *xce, evtchn_port_t port);
>>    */
>>   int xenevtchn_restrict(xenevtchn_handle *xce, domid_t domid);
>>   
>> +/**
>> + * Bind an event channel under Mini-OS.
>> + *
>> + * Bind an event channel specified by its known port after a kexec() of
>> + * Mini-OS. This function is available under Mini-OS only!
> 
> Would guarding this prototype within "#ifdef __MINIOS__" be useful to
> prevent it from been used? That would give an error earlier when
> compiling, rather than later when linking a binary.

Yes, I can add that.

> 
> In anycase: Acked-by: Anthony PERARD <anthony.perard@vates.tech>

Thanks,


Juergen

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[PATCH v2 6/9] xenstored: rebind event channels after live update in stubdom

[Juergen Gross]

After performing a live update in stubdom environment some information
about inter-domain event channels is lost. In order to set this
information again, call xenevtchn_bind() from new_domain() in the
restore case.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>
---
 tools/xenstored/core.c   | 1 -
 tools/xenstored/core.h   | 3 +++
 tools/xenstored/domain.c | 8 ++++++--
 tools/xenstored/minios.c | 5 +++++
 tools/xenstored/posix.c  | 5 +++++
 5 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/tools/xenstored/core.c b/tools/xenstored/core.c
index 3022efdce1..e3e8607592 100644
--- a/tools/xenstored/core.c
+++ b/tools/xenstored/core.c
@@ -49,7 +49,6 @@
 #include "control.h"
 #include "lu.h"
 
-extern xenevtchn_handle *xce_handle; /* in domain.c */
 static int xce_pollfd_idx = -1;
 struct pollfd *poll_fds;
 static unsigned int current_array_size;
diff --git a/tools/xenstored/core.h b/tools/xenstored/core.h
index bef24a688c..3f7426fbe3 100644
--- a/tools/xenstored/core.h
+++ b/tools/xenstored/core.h
@@ -394,6 +394,8 @@ static inline bool domain_is_unprivileged(const struct connection *conn)
 	return conn && domid_is_unprivileged(conn->id);
 }
 
+extern xenevtchn_handle *xce_handle; /* in domain.c */
+
 /* Return the event channel used by xenbus. */
 evtchn_port_t get_xenbus_evtchn(void);
 void early_init(bool live_update, bool dofork, const char *pidfile);
@@ -407,6 +409,7 @@ int get_socket_fd(void);
 void set_socket_fd(int fd);
 
 xenevtchn_handle *evtchn_fdopen(int fd);
+int evtchn_rebind(int port);
 
 #ifdef __MINIOS__
 void mount_9pfs(void);
diff --git a/tools/xenstored/domain.c b/tools/xenstored/domain.c
index 6767d29a19..7a6ce5b91b 100644
--- a/tools/xenstored/domain.c
+++ b/tools/xenstored/domain.c
@@ -862,9 +862,13 @@ static int new_domain(struct domain *domain, int port, bool restore)
 
 	wrl_domain_new(domain);
 
-	if (restore)
+	if (restore) {
+		if (evtchn_rebind(port)) {
+			errno = ENOMEM;
+			return errno;
+		}
 		domain->port = port;
-	else {
+	} else {
 		/* Tell kernel we're interested in this event. */
 		rc = xenevtchn_bind_interdomain(xce_handle, domain->domid,
 						port);
diff --git a/tools/xenstored/minios.c b/tools/xenstored/minios.c
index aa1f03fd6b..ec5faebaf3 100644
--- a/tools/xenstored/minios.c
+++ b/tools/xenstored/minios.c
@@ -90,6 +90,11 @@ xenevtchn_handle *evtchn_fdopen(int fd)
 	return xenevtchn_open(NULL, XENEVTCHN_NO_CLOEXEC);
 }
 
+int evtchn_rebind(int port)
+{
+	return xenevtchn_bind(xce_handle, port);
+}
+
 static void mount_thread(void *p)
 {
 	xenbus_event_queue events = NULL;
diff --git a/tools/xenstored/posix.c b/tools/xenstored/posix.c
index ebdec82215..97561701ae 100644
--- a/tools/xenstored/posix.c
+++ b/tools/xenstored/posix.c
@@ -413,6 +413,11 @@ xenevtchn_handle *evtchn_fdopen(int fd)
 	return xenevtchn_fdopen(NULL, fd, 0);
 }
 
+int evtchn_rebind(int port)
+{
+	return 0;
+}
+
 const char *xenstore_rundir(void)
 {
 	return xenstore_daemon_rundir();
-- 
2.43.0

[PATCH v2 7/9] tools/xenstored: make stubdom_init() live update aware

[Juergen Gross]

Pass the live_update bool to stubdom_init() in order to be able to
handle it properly under Mini-OS.

As stubdom_init() will (re-)create the 9pfs device needed for
reading the saved state, call stubdom_init() before lu_read_state().

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>
---
 tools/xenstored/core.c   |  4 ++--
 tools/xenstored/core.h   |  2 +-
 tools/xenstored/domain.c | 15 +++++++++------
 tools/xenstored/domain.h |  2 +-
 tools/xenstored/minios.c | 12 +++++++++---
 5 files changed, 22 insertions(+), 13 deletions(-)

diff --git a/tools/xenstored/core.c b/tools/xenstored/core.c
index e3e8607592..5377d72f54 100644
--- a/tools/xenstored/core.c
+++ b/tools/xenstored/core.c
@@ -2774,14 +2774,14 @@ int main(int argc, char *argv[])
 	if (tracefile)
 		tracefile = absolute_filename(NULL, tracefile);
 
+	stubdom_init(live_update);
+
 #ifndef NO_LIVE_UPDATE
 	/* Read state in case of live update. */
 	if (live_update)
 		lu_read_state();
 #endif
 
-	stubdom_init();
-
 	check_store();
 
 	/* Get ready to listen to the tools. */
diff --git a/tools/xenstored/core.h b/tools/xenstored/core.h
index 3f7426fbe3..5071f1dedd 100644
--- a/tools/xenstored/core.h
+++ b/tools/xenstored/core.h
@@ -412,7 +412,7 @@ xenevtchn_handle *evtchn_fdopen(int fd);
 int evtchn_rebind(int port);
 
 #ifdef __MINIOS__
-void mount_9pfs(void);
+void mount_9pfs(bool live_update);
 #endif
 
 const char *xenstore_rundir(void);
diff --git a/tools/xenstored/domain.c b/tools/xenstored/domain.c
index 7a6ce5b91b..57ca98ee5b 100644
--- a/tools/xenstored/domain.c
+++ b/tools/xenstored/domain.c
@@ -1337,7 +1337,7 @@ void dom0_init(void)
 	xenevtchn_notify(xce_handle, dom0->port);
 }
 
-void stubdom_init(void)
+void stubdom_init(bool live_update)
 {
 #ifdef __MINIOS__
 	struct domain *stubdom;
@@ -1345,13 +1345,16 @@ void stubdom_init(void)
 	if (stub_domid < 0)
 		return;
 
-	stubdom = introduce_domain(NULL, stub_domid, xenbus_evtchn, false);
-	if (!stubdom)
-		barf_perror("Failed to initialize stubdom");
+	if (!live_update) {
+		stubdom = introduce_domain(NULL, stub_domid, xenbus_evtchn,
+					   false);
+		if (!stubdom)
+			barf_perror("Failed to initialize stubdom");
 
-	xenevtchn_notify(xce_handle, stubdom->port);
+		xenevtchn_notify(xce_handle, stubdom->port);
+	}
 
-	mount_9pfs();
+	mount_9pfs(live_update);
 #endif
 }
 
diff --git a/tools/xenstored/domain.h b/tools/xenstored/domain.h
index 94481fdcc0..3ca702f56d 100644
--- a/tools/xenstored/domain.h
+++ b/tools/xenstored/domain.h
@@ -93,7 +93,7 @@ int do_set_feature(const void *ctx, struct connection *conn,
 void domain_early_init(void);
 void domain_init(int evtfd);
 void dom0_init(void);
-void stubdom_init(void);
+void stubdom_init(bool live_update);
 void domain_deinit(void);
 void ignore_connection(struct connection *conn, unsigned int err);
 
diff --git a/tools/xenstored/minios.c b/tools/xenstored/minios.c
index ec5faebaf3..f04423fe09 100644
--- a/tools/xenstored/minios.c
+++ b/tools/xenstored/minios.c
@@ -131,15 +131,21 @@ static void mount_thread(void *p)
 		free(err);
 	}
 
-	p9_device = init_9pfront(0, XENSTORE_LIB_DIR);
+	p9_device = init_9pfront2(0, XENSTORE_LIB_DIR, INIT9P_FLAG_KEXEC);
 
 	/* Start logging if selected. */
 	reopen_log();
 }
 
-void mount_9pfs(void)
+void mount_9pfs(bool live_update)
 {
-	create_thread("mount-9pfs", mount_thread, NULL);
+	if (!live_update)
+		create_thread("mount-9pfs", mount_thread, NULL);
+	else {
+		p9_device = init_9pfront2(0, XENSTORE_LIB_DIR,
+					  INIT9P_FLAG_REINIT);
+		reopen_log();
+	}
 }
 
 const char *xenstore_rundir(void)
-- 
2.43.0

[PATCH v2 8/9] SUPPORT.md: add xenstorepvh-stubdom live update

[Juergen Gross]

Live update is now working with the PVH variant of xenstore-stubdom.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
V2:
- new patch
---
 SUPPORT.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/SUPPORT.md b/SUPPORT.md
index 6a82a92189..eb44ee85fd 100644
--- a/SUPPORT.md
+++ b/SUPPORT.md
@@ -280,7 +280,7 @@ or itself will not be regarded a security issue.
 ### C xenstore stubdom PVH
 
     Status: Supported
-    Status, Liveupdate: Not implemented
+    Status, Liveupdate: Supported
 
 ### OCaml xenstored daemon
 
-- 
2.43.0

[PATCH v2 9/9] CHANGELOG.md: add xenstorepvh-stubdom live update

[Juergen Gross]

Signed-off-by: Juergen Gross <jgross@suse.com>
---
V2:
- new patch
---
 CHANGELOG.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5f31ca08fe..d118bb1c8c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -26,6 +26,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
    - Support PCI passthrough for HVM domUs when dom0 is PVH (note SR-IOV
      capability usage is not yet supported on PVH dom0).
    - Smoke tests for the FreeBSD Xen builds in Cirrus CI.
+   - PVH xenstore-stubdom now supports Live Update.
 
  - On Arm:
     - Ability to enable stack protector
-- 
2.43.0