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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v2 1/2] xenconsoled: use grant references instead of map_foreign_range
On Thu, 10 Jan 2013, Daniel De Graaf wrote:
> Grant references for the xenstore and xenconsole shared pages exist, but
> currently only xenstore uses these references. Change the xenconsole
> daemon to prefer using the grant reference over map_foreign_range when
> mapping the shared console ring.
>
> This allows xenconsoled to be run in a domain other than dom0 if set up
> correctly - for libxl, the xenstore path /tool/xenconsoled/domid
> specifies the domain containing xenconsoled.
Unfortunately at the moment xc_dom_gnttab_init doesn't work with an
autotranslated dom0, that is the only type of dom0 that you get on ARM.
As a consequence this patch would break xenconsoled on ARM. I expect the
same to happen with PVH as well.
I also have the same issue with xenstored and I was thinking about
writing a patch to make it gracefully fallback to xc_map_foreign_range
if xc_gnttab_map_grant_ref fails.
The reason why xc_dom_gnttab_init is broken is that it uses
xc_map_foreign_range to map the grant table page of the foreign domain,
that is not a regular gpfn page, therefore it fails.
Specifically on ARM it hits the case XENMAPSPACE_gmfn_foreign in
xenmem_add_to_physmap_one, then it fails the p2m lookup and returns
EINVAL.
Do you feel up for making xc_dom_gnttab_init work for an autotranslated
dom0?
Otherwise I think that for the moment is best to modify this patch to
gracefully fallback to xc_map_foreign_range. Then we need a couple of
other patches to do the same with xenstored and libxl.
> Signed-off-by: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
> Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> Cc: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> Cc: Ian Campbell <ian.campbell@xxxxxxxxxx>
> ---
> tools/console/daemon/io.c | 48
> ++++++++++++++++++++++++++++++++++++++-------
> tools/console/daemon/io.h | 1 -
> tools/console/daemon/main.c | 2 --
> 3 files changed, 41 insertions(+), 10 deletions(-)
>
> diff --git a/tools/console/daemon/io.c b/tools/console/daemon/io.c
> index 48fe151..e1720b6 100644
> --- a/tools/console/daemon/io.c
> +++ b/tools/console/daemon/io.c
> @@ -24,6 +24,7 @@
> #include "io.h"
> #include <xenstore.h>
> #include <xen/io/console.h>
> +#include <xen/grant_table.h>
>
> #include <stdlib.h>
> #include <errno.h>
> @@ -69,6 +70,7 @@ static int log_hv_fd = -1;
> static evtchn_port_or_error_t log_hv_evtchn = -1;
> static xc_interface *xch; /* why does xenconsoled have two xc handles ? */
> static xc_evtchn *xce_handle = NULL;
> +static xc_gnttab *xcg_handle = NULL;
>
> struct buffer {
> char *data;
> @@ -501,6 +503,18 @@ static int xs_gather(struct xs_handle *xs, const char
> *dir, ...)
> va_end(ap);
> return ret;
> }
> +
> +static void domain_unmap_interface(struct domain *dom)
> +{
> + if (dom->interface == NULL)
> + return;
> + if (xcg_handle && dom->ring_ref == -1)
> + xc_gnttab_munmap(xcg_handle, dom->interface, 1);
> + else
> + munmap(dom->interface, getpagesize());
> + dom->interface = NULL;
> + dom->ring_ref = -1;
> +}
>
> static int domain_create_ring(struct domain *dom)
> {
> @@ -522,9 +536,19 @@ static int domain_create_ring(struct domain *dom)
> }
> free(type);
>
> - if (ring_ref != dom->ring_ref) {
> - if (dom->interface != NULL)
> - munmap(dom->interface, getpagesize());
> + /* If using ring_ref and it has changed, remap */
> + if (ring_ref != dom->ring_ref && dom->ring_ref != -1)
> + domain_unmap_interface(dom);
> +
> + if (!dom->interface && xcg_handle) {
> + /* Prefer using grant table */
> + dom->interface = xc_gnttab_map_grant_ref(xcg_handle,
> + dom->domid, GNTTAB_RESERVED_CONSOLE,
> + PROT_READ|PROT_WRITE);
> + dom->ring_ref = -1;
> + }
> + if (!dom->interface) {
> + /* Fall back to xc_map_foreign_range */
> dom->interface = xc_map_foreign_range(
> xc, dom->domid, getpagesize(),
> PROT_READ|PROT_WRITE,
> @@ -720,9 +744,7 @@ static void shutdown_domain(struct domain *d)
> {
> d->is_dead = true;
> watch_domain(d, false);
> - if (d->interface != NULL)
> - munmap(d->interface, getpagesize());
> - d->interface = NULL;
> + domain_unmap_interface(d);
> if (d->xce_handle != NULL)
> xc_evtchn_close(d->xce_handle);
> d->xce_handle = NULL;
> @@ -730,7 +752,7 @@ static void shutdown_domain(struct domain *d)
>
> static unsigned enum_pass = 0;
>
> -void enum_domains(void)
> +static void enum_domains(void)
> {
> int domid = 1;
> xc_dominfo_t dominfo;
> @@ -957,6 +979,14 @@ void handle_io(void)
> }
> }
>
> + xcg_handle = xc_gnttab_open(NULL, 0);
> + if (xcg_handle == NULL) {
> + dolog(LOG_DEBUG, "Failed to open xcg handle: %d (%s)",
> + errno, strerror(errno));
> + }
> +
> + enum_domains();
> +
> for (;;) {
> struct domain *d, *n;
> int max_fd = -1;
> @@ -1097,6 +1127,10 @@ void handle_io(void)
> xc_evtchn_close(xce_handle);
> xce_handle = NULL;
> }
> + if (xcg_handle != NULL) {
> + xc_gnttab_close(xcg_handle);
> + xcg_handle = NULL;
> + }
> log_hv_evtchn = -1;
> }
>
> diff --git a/tools/console/daemon/io.h b/tools/console/daemon/io.h
> index 8fa04b6..f658bfc 100644
> --- a/tools/console/daemon/io.h
> +++ b/tools/console/daemon/io.h
> @@ -21,7 +21,6 @@
> #ifndef CONSOLED_IO_H
> #define CONSOLED_IO_H
>
> -void enum_domains(void);
> void handle_io(void);
>
> #endif
> diff --git a/tools/console/daemon/main.c b/tools/console/daemon/main.c
> index 789baa6..92d2fc4 100644
> --- a/tools/console/daemon/main.c
> +++ b/tools/console/daemon/main.c
> @@ -161,8 +161,6 @@ int main(int argc, char **argv)
> if (!xen_setup())
> exit(1);
>
> - enum_domains();
> -
> handle_io();
>
> closelog();
> --
> 1.7.11.7
>
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