On 2021/12/20 4:29 PM, lijiang wrote:
Hi, Qi
Thank you for the fix.

Date: Thu, 16 Dec 2021 15:09:49 +0800
From: Qi Zheng <[email protected]>
To: [email protected], [email protected], [email protected]
Cc: Qi Zheng <[email protected]>, [email protected]
Subject: [Crash-utility] [PATCH] Fix pvops Xen detection for arm
         machine
Message-ID: <[email protected]>
Content-Type: text/plain; charset="US-ASCII"

Since the xen_start_info on the arm/arm64 platform is static defined:

./arm/xen/enlighten.c:40:static struct start_info _xen_start_info;
./arm/xen/enlighten.c:41:struct start_info *xen_start_info = &_xen_start_info;
./arm/xen/enlighten.c:42:EXPORT_SYMBOL(xen_start_info);

The above variable is statically defined in the kernel, but the
'xen_vcpu_info' is also a static variable, why does the former not
work on arm machines, but the latter works well? Could you please
explain more details?
[linux]$ grep -nr "xen_vcpu_info" *
arch/arm/xen/enlighten.c:51:static struct vcpu_info __percpu *xen_vcpu_info;

Hi Lianbo,

The 'xen_vcpu_info' is also a static variable on the arm/arm64 platform,
but different from 'xen_start_info', it is assigned during the
initialization process.

Thanks,
Qi


Thanks.
Lianbo

The is_pvops_xen() in commit 4badc6229c69f5cd9da7eb7bdf400a53ec6db01a
("Fix pvops Xen detection for kernels >= v4.20") always return TRUE.
Then the following error will be reported because p2m_mid_missing
and xen_p2m_addr are not defined:

         crash: cannot resolve "p2m_top"

For the arm/arm64 platform, fix it by using xen_vcpu_info instead of
xen_start_info to detect Xen dumps.

Signed-off-by: Qi Zheng <[email protected]>
---
  kernel.c | 15 +++++++++++----
  1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/kernel.c b/kernel.c
index f4598ea..4b4d789 100644
--- a/kernel.c
+++ b/kernel.c
@@ -10757,11 +10757,18 @@ is_pvops_xen(void)
              STREQ(sym, "paravirt_patch_default")))
                 return TRUE;

-       if (symbol_exists("xen_start_info") &&
-           readmem(symbol_value("xen_start_info"), KVADDR, &addr,
-           sizeof(void *), "xen_start_info", RETURN_ON_ERROR) &&
-           addr != 0)
+       if (machine_type("ARM") || machine_type("ARM64")) {
+               if (symbol_exists("xen_vcpu_info") &&
+                   readmem(symbol_value("xen_vcpu_info"), KVADDR, &addr,
+                   sizeof(void *), "xen_vcpu_info", RETURN_ON_ERROR) &&
+                   addr != 0)
+                       return TRUE;
+       } else if (symbol_exists("xen_start_info") &&
+                  readmem(symbol_value("xen_start_info"), KVADDR, &addr,
+                  sizeof(void *), "xen_start_info", RETURN_ON_ERROR) &&
+                  addr != 0) {
                 return TRUE;
+       }

         return FALSE;
  }
--
2.11.0


--
Thanks,
Qi

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