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

-----Original Message----- > On 12/16/21 2:36 PM, Qi Zheng wrote: >> >> >> On 12/15/21 3:42 PM, HAGIO KAZUHITO(萩尾 一仁) wrote: >>> Hi Qi, Xen folks, >>> >>> -----Original Message----- >>>> 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 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" >>>> >>>> Fix it by using xen_vcpu_id instead of xen_start_info to detect Xen >>>> dumps. >>>> >>>> Signed-off-by: Qi Zheng <zhengqi.arch(a)bytedance.com&gt; >>>> --- >>>>   kernel.c | 21 ++++++++++++++++----- >>>>   1 file changed, 16 insertions(+), 5 deletions(-) >>>> >>>> diff --git a/kernel.c b/kernel.c >>>> index f4598ea..b216fbe 100644 >>>> --- a/kernel.c >>>> +++ b/kernel.c >>>> @@ -10745,6 +10745,9 @@ is_pvops_xen(void) >>>>   { >>>>       ulong addr; >>>>       char *sym; >>>> +    struct syment * sp; >>>> +    ulong ptr; >>>> +    int i; >>>> >>>>       if (!PVOPS()) >>>>           return FALSE; >>>> @@ -10757,11 +10760,19 @@ 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) >>>> -        return TRUE; >>>> +    sp = per_cpu_symbol_search("xen_vcpu_id"); >>>> +    if (sp) { >>>> +        for (i = 0; i < NR_CPUS; i++) { >>>> +            if (!kt->__per_cpu_offset[i]) >>>> +                continue; >>> >>> Thanks for the patch. >>> >>> But seems that kt->__per_cpu_offset is initialized after the >>> is_pvops_xen() >>> call.  So this block always return FALSE? >>> >>> Is there any other variable that we can use?  or another solution.. >> >> Or use xen_vcpu_info for arm/arm64 machine and xen_start_info for x86 >> machine? Both of these variables are assigned during the initialization >> path. > > Like this: > > 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; > } > > If it make sense, I can send the next version. Nice, looks good to me.

Thanks, Kazu