[PATCH RFC] xen/vsprintf: Introduce %pd formatter for domains

* [PATCH RFC] xen/vsprintf: Introduce %pd formatter for domains
@ 2018-08-30 13:06 Andrew Cooper
  2018-08-30 14:18 ` Jan Beulich
  0 siblings, 1 reply; 3+ messages in thread
From: Andrew Cooper @ 2018-08-30 13:06 UTC (permalink / raw)
  To: Xen-devel
  Cc: Stefano Stabellini, Wei Liu, George Dunlap, Andrew Cooper,
	Tim Deegan, Julien Grall, Jan Beulich

This allows all system domids to be printed by name, rather than special
casing the idle vcpus alone.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: George Dunlap <George.Dunlap@eu.citrix.com>
CC: Jan Beulich <JBeulich@suse.com>
CC: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
CC: Stefano Stabellini <sstabellini@kernel.org>
CC: Tim Deegan <tim@xen.org>
CC: Wei Liu <wei.liu2@citrix.com>
CC: Julien Grall <julien.grall@arm.com>

RFC, because this was proposed before but rejected at the time.  I'm looking
to try and turn errors like this:

  (XEN) mm.c:1023:d0v2 pg_owner d32754 l1e_owner d0, but real_pg_owner d0
  (XEN) mm.c:1099:d0v2 Error getting mfn 810020 (pfn 59db1) from L1 entry 8000000810020227 for l1e_owner d0, pg_owner d32754

into the slightly more helpful:

  (XEN) mm.c:1022:d0v2 pg_owner dXEN l1e_owner d0, but real_pg_owner d0
  (XEN) mm.c:1098:d0v2 Error getting mfn 810020 (pfn 59db1) from L1 entry 8000000810020227 for l1e_owner d0, pg_owner dXEN

although even in this case, the former printk has an awkward corner case of a
possibly NULL domain pointer, which can possibly only reasonably be fixed
inside pointer() itself.

# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
#
# Date:      Wed Aug 29 16:16:50 2018 +0000
#
# On branch xen-pd
# Your branch is ahead of 'origin/staging' by 1 commit.
#   (use "git push" to publish your local commits)
#
# Changes to be committed:
#	modified:   ../docs/misc/printk-formats.txt
#	modified:   common/vsprintf.c
#
# Untracked files:
#	System.map-after
#	System.map-before
#	dis-after
#	dis-before
#	headers-after
#	headers-before
#	include/asm-x86/asm-macros.h
#	wl-a
#	wl-b
#	xen-after
#	xen-before
#	xen-syms-after
#	xen-syms-before
#
---
 docs/misc/printk-formats.txt |  3 +++
 xen/common/vsprintf.c        | 57 +++++++++++++++++++++++++++++++++++---------
 2 files changed, 49 insertions(+), 11 deletions(-)

diff --git a/docs/misc/printk-formats.txt b/docs/misc/printk-formats.txt
index 525108f..6d2c617 100644
--- a/docs/misc/printk-formats.txt
+++ b/docs/misc/printk-formats.txt
@@ -28,5 +28,8 @@ Symbol/Function pointers:
 
 Domain and vCPU information:
 
+       %pd     Domain from a 'struct domain *d' (printed as d<domid>, but with
+               system domains represented by name, e.g. 'dIDLE')
+
        %pv     Domain and vCPU ID from a 'struct vcpu *' (printed as
                "d<domid>v<vcpuid>")
diff --git a/xen/common/vsprintf.c b/xen/common/vsprintf.c
index f92fb67..918a39d 100644
--- a/xen/common/vsprintf.c
+++ b/xen/common/vsprintf.c
@@ -264,6 +264,41 @@ static char *string(char *str, char *end, const char *s,
     return str;
 }
 
+/* Print a domain as d<num> or d<str> for system domains. */
+static char *print_domain(char *str, char *end, const struct domain *d)
+{
+    const char *name = NULL;
+
+    if ( str < end )
+        *str++ = 'd';
+
+    switch ( d->domain_id )
+    {
+    case DOMID_SELF:    name = "SELF";    break;
+    case DOMID_IO:      name = "IO";      break;
+    case DOMID_XEN:     name = "XEN";     break;
+    case DOMID_COW:     name = "COW";     break;
+    case DOMID_INVALID: name = "INVALID"; break;
+    case DOMID_IDLE:    name = "IDLE";    break;
+    }
+
+    if ( name )
+        return string(str, end, name, -1, -1, 0);
+    else
+        return number(str, end, d->domain_id, 10, -1, -1, 0);
+}
+
+/* Print a vcpu as d<domain-id>v<vcpu-id> */
+static char *print_vcpu(char *str, char *end, const struct vcpu *v)
+{
+    str = print_domain(str, end, v->domain);
+
+    if ( str < end )
+        *str = 'v';
+
+    return number(str + 1, end, v->vcpu_id, 10, -1, -1, 0);
+}
+
 static char *pointer(char *str, char *end, const char **fmt_ptr,
                      const void *arg, int field_width, int precision,
                      int flags)
@@ -273,6 +308,15 @@ static char *pointer(char *str, char *end, const char **fmt_ptr,
     /* Custom %p suffixes. See XEN_ROOT/docs/misc/printk-formats.txt */
     switch ( fmt[1] )
     {
+    case 'd': /* d<domain-id> from a struct domain */
+    {
+        const struct domain *d = arg;
+
+        ++*fmt_ptr;
+
+        return print_domain(str, end, d);
+    }
+
     case 'h': /* Raw buffer as hex string. */
     {
         const uint8_t *hex_buffer = arg;
@@ -374,17 +418,8 @@ static char *pointer(char *str, char *end, const char **fmt_ptr,
         const struct vcpu *v = arg;
 
         ++*fmt_ptr;
-        if ( unlikely(v->domain->domain_id == DOMID_IDLE) )
-            str = string(str, end, "IDLE", -1, -1, 0);
-        else
-        {
-            if ( str < end )
-                *str = 'd';
-            str = number(str + 1, end, v->domain->domain_id, 10, -1, -1, 0);
-        }
-        if ( str < end )
-            *str = 'v';
-        return number(str + 1, end, v->vcpu_id, 10, -1, -1, 0);
+
+        return print_vcpu(str, end, v);
     }
     }
 
-- 
2.1.4


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