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

[lijiang]

Hi, Qi
Thank you for the fix.

> Date: Thu, 16 Dec 2021 15:09:49 +0800
> From: Qi Zheng <zhengqi.arch at bytedance.com>
> To: k-hagio-ab at nec.com, ptesarik at suse.com, lijiang at redhat.com
> Cc: Qi Zheng <zhengqi.arch at bytedance.com>, crash-utility at redhat.com
> Subject: [Crash-utility] [PATCH] Fix pvops Xen detection for arm
>         machine
> Message-ID: <20211216070949.17668-1-zhengqi.arch at bytedance.com>
> 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;

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 at bytedance.com>
> ---
>  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