Re: [Crash-utility] [PATCH] Fix pvops Xen detection for arm machine

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 <zhengqi.arch(a)bytedance.com&gt; >> To: k-hagio-ab(a)nec.com, ptesarik(a)suse.com, lijiang(a)redhat.com >> Cc: Qi Zheng <zhengqi.arch(a)bytedance.com&gt;, crash-utility(a)redhat.com >> Subject: [Crash-utility] [PATCH] Fix pvops Xen detection for arm >>          machine >> Message-ID: <20211216070949.17668-1-zhengqi.arch(a)bytedance.com&gt; >> 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 <zhengqi.arch(a)bytedance.com&gt; >> --- >>   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 >