[Xen-changelog] [xen staging] xentrace: handle sparse cpu ids correctly in xen trace buffer handling

[patchbot@xxxxxxx]

commit 74584a367051bc0d6f4b96fd360fa7bc6538fc39
Author:     Juergen Gross <jgross@xxxxxxxx>
AuthorDate: Thu Oct 4 12:47:24 2018 +0100
Commit:     George Dunlap <george.dunlap@xxxxxxxxxx>
CommitDate: Thu Oct 4 12:47:24 2018 +0100

    xentrace: handle sparse cpu ids correctly in xen trace buffer handling
    
    The per-cpu buffers for Xentrace are addressed by cpu-id, but the info
    array for the buffers is sized only by number of online cpus. This
    might lead to crashes when using Xentrace with smt=0.
    
    The t_info structure has to be sized based on nr_cpu_ids.
    
    Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
    Reviewed-by: George Dunlap <george.dunlap@xxxxxxxxxx>
---
 tools/xentrace/xentrace.c | 2 +-
 xen/common/trace.c        | 8 ++++----
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/tools/xentrace/xentrace.c b/tools/xentrace/xentrace.c
index a9cb4b15a9..4b50b8a53e 100644
--- a/tools/xentrace/xentrace.c
+++ b/tools/xentrace/xentrace.c
@@ -600,7 +600,7 @@ static unsigned int get_num_cpus(void)
         exit(EXIT_FAILURE);
     }
 
-    return physinfo.nr_cpus;
+    return physinfo.max_cpu_id + 1;
 }
 
 /**
diff --git a/xen/common/trace.c b/xen/common/trace.c
index 8cdc17b731..cc294fc384 100644
--- a/xen/common/trace.c
+++ b/xen/common/trace.c
@@ -113,7 +113,7 @@ static int calculate_tbuf_size(unsigned int pages, uint16_t 
t_info_first_offset)
     struct t_info dummy_pages;
     typeof(dummy_pages.tbuf_size) max_pages;
     typeof(dummy_pages.mfn_offset[0]) max_mfn_offset;
-    unsigned int max_cpus = num_online_cpus();
+    unsigned int max_cpus = nr_cpu_ids;
     unsigned int t_info_words;
 
     /* force maximum value for an unsigned type */
@@ -149,13 +149,13 @@ static int calculate_tbuf_size(unsigned int pages, 
uint16_t t_info_first_offset)
 
     /* 
      * NB this calculation is correct, because t_info_first_offset is
-     * in words, not bytes, not bytes
+     * in words, not bytes
      */
-    t_info_words = num_online_cpus() * pages + t_info_first_offset;
+    t_info_words = nr_cpu_ids * pages + t_info_first_offset;
     t_info_pages = PFN_UP(t_info_words * sizeof(uint32_t));
     printk(XENLOG_INFO "xentrace: requesting %u t_info pages "
            "for %u trace pages on %u cpus\n",
-           t_info_pages, pages, num_online_cpus());
+           t_info_pages, pages, nr_cpu_ids);
     return pages;
 }
 
--
generated by git-patchbot for /home/xen/git/xen.git#staging

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