[Crash-utility] Re: [PATCH v7 01/15] Fix the regression of cpumask_t for xen hyper

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Hi Tao,

On 05/09/24 03:40, Tao Liu wrote:
Hi Aditya,

On Wed, Sep 4, 2024 at 10:27 PM Aditya Gupta <adityag@xxxxxxxxxxxxx> wrote:
Hi Tao,

Is this a separate independent patch or related to this series ?

This is an independent patch, but discovered when doing a regression
test against the stack unwinding patchset. Since we have done the
cpumask_t modification in [PATCH v6 10/14], the modification will
continue in v7 as well. So I posted it with v7 together.

Lianbo suggested that I separate some "less strongly connected with
stack unwinding" patches from v7, which formed the part 1 as mentioned
in [1]. Part 1 can be merged prior to the rest of part 2 & 3. So I
think part 1 is also suitable for the cpumask_t regression patch.

Yes, I agree. We can move 'Fix gdb_interface' patch also as independent. It originally was required for the patch series to work, since 'info threads' used to break, but now that can go independently.


Thanks,

Aditya Gupta

[1]: https://www.mail-archive.com/devel@xxxxxxxxxxxxxxxxxxxxxxxxxxx/msg01079.html

Thanks,
Tao Liu

- Aditya Gupta


On 04/09/24 13:19, Tao Liu wrote:
There is a regression been found for xen hyper due to the commit:
f615f8fab7bf ("Fix "irq -a" exceeding the memory range issue").

The reason is for xen hyper, kt->cpu is not initialized due to
kernel_init() won't be called. So 0 would be assigned to cpulen and
fails the GETBUF().

Before:
crash> bt -c 2
bt: zero-size memory allocation! (called from 51f168)

After:
crash> bt -c 2
PCPU:  0  VCPU: ffff8300001b8080
   #0 [ffff8300001bfe00] machine_crash_kexec at ffff83000010de72
   #1 [ffff8300001bfe10] do_kexec_op at ffff83000010e3cb
   #2 [ffff8300001bfe50] do_console_io at ffff83000011aff4
   #3 [ffff8300001bfe90] mod_l1_entry at ffff830000129045
   #4 [ffff8300001bfea0] toggle_guest_mode at ffff8300001641bf
   #5 [ffff8300001bfeb0] do_iret at ffff830000164888
   #6 [ffff8300001bff20] syscall_enter at ffff8300001633d2

Since xen hyper will initialize its own cpumask_t, this patch will reuse
it for XEN_HYPER_MODE. In addition, this patch won't modify the similar
code hunk in generic_get_irq_affinity(), because for xen, there is no
"irq" cmd, so the regression won't be triggered.

Cc: Sourabh Jain <sourabhjain@xxxxxxxxxxxxx>
Cc: Hari Bathini <hbathini@xxxxxxxxxxxxx>
Cc: Mahesh J Salgaonkar <mahesh@xxxxxxxxxxxxx>
Cc: Naveen N. Rao <naveen.n.rao@xxxxxxxxxxxxxxxxxx>
Cc: Lianbo Jiang <lijiang@xxxxxxxxxx>
Cc: HAGIO KAZUHITO(萩尾 一仁) <k-hagio-ab@xxxxxxx>
Cc: Tao Liu <ltao@xxxxxxxxxx>
Cc: Alexey Makhalov <alexey.makhalov@xxxxxxxxxxxx>
Cc: Aditya Gupta <adityag@xxxxxxxxxxxxx>
Signed-off-by: Tao Liu <ltao@xxxxxxxxxx>
---
   tools.c | 6 ++++++
   1 file changed, 6 insertions(+)

diff --git a/tools.c b/tools.c
index 2b78b95..dec6e5b 100644
--- a/tools.c
+++ b/tools.c
@@ -16,6 +16,7 @@
    */

   #include "defs.h"
+#include "xen_hyper_defs.h"
   #include <ctype.h>

   #ifdef VALGRIND
@@ -6720,6 +6721,11 @@ get_cpumask_buf(void)
   {
       int cpulen, len_cpumask;

+#ifdef XEN_HYPERVISOR_ARCH
+     if (XEN_HYPER_MODE() && XEN_HYPER_VALID_SIZE(cpumask_t))
+             return (ulong *)GETBUF(XEN_HYPER_SIZE(cpumask_t));
+#endif
+
       cpulen = DIV_ROUND_UP(kt->cpus, BITS_PER_LONG) * sizeof(ulong);
       len_cpumask = STRUCT_SIZE("cpumask_t");
       if (len_cpumask > 0)
--
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