On 2021/12/21 2:53 PM, lijiang wrote:
On Mon, Dec 20, 2021 at 5:26 PM Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx> wrote:
On 2021/12/20 4:35 PM, Qi Zheng wrote:
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@xxxxxxxxxxxxx>
To: k-hagio-ab@xxxxxxx, ptesarik@xxxxxxxx, lijiang@xxxxxxxxxx
Cc: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>, crash-utility@xxxxxxxxxx
Subject: [PATCH] Fix pvops Xen detection for arm
machine
Message-ID: <20211216070949.17668-1-zhengqi.arch@xxxxxxxxxxxxx>
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.
Like the 'xen_start_info' on the x86 platform:
- definition:
struct start_info *xen_start_info;
EXPORT_SYMBOL_GPL(xen_start_info);
- initialization:
startup_xen
--> mov %rsi, xen_start_info
The 'xen_vcpu_info' on the arm/arm64 platform:
- definition:
static struct vcpu_info __percpu *xen_vcpu_info;
- initialization:
xen_guest_init
--> xen_vcpu_info = alloc_percpu(struct vcpu_info);
So I think that it will works well on the arm/arm64 platform. I have
tested it on the arm64 platform(But I can not test it on the arm/arm64
xen machine).
Thank you for the explanation, Qi.
The xen_start_info is only defined in x86 and arm platform, but
because the xen_start_info on the arm/arm64 platform points to a
static variable '_xen_start_info'(see its definition as below), which
makes that the address of xen_start_info will never be null. As a
result, the is_pvops_xen() in in commit 4badc6229c69 ("Fix pvops Xen
detection for kernels >= v4.20") always returns TRUE, the reason is
that it can always read out the non-null address of xen_start_info,
and finally caused the failure.
[linux]$ grep -nrw "xen_start_info" *
arch/arm/xen/enlighten.c:41:struct start_info *xen_start_info =
&_xen_start_info;
arch/arm/xen/enlighten.c:42:EXPORT_SYMBOL(xen_start_info);
...
arch/x86/xen/enlighten.c:49:struct start_info *xen_start_info;
arch/x86/xen/enlighten.c:50:EXPORT_SYMBOL_GPL(xen_start_info);
In view of this, it could be better to explicitly narrow the
'xen_start_info' check to x86 with the machine_type(), there is no
need to check it on other architectures. What do you think?
LGTM, I will send the patch v3.
Thanks,
Qi
For example:
diff --git a/kernel.c b/kernel.c
index f4598ea217a3..b17f3fb9e85e 100644
--- a/kernel.c
+++ b/kernel.c
@@ -10757,11 +10757,22 @@ 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;
+ if (machine_type("X86") || machine_type("X86_64")) {
+ 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;
+ }
+
+ 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;
+ }
+
return FALSE;
}
Although the above if(machine_type("ARM")) block has not been tested
on the arm Xen platform, it doesn't affect other architectures.
Thanks.
Lianbo
Thanks,
Qi
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@xxxxxxxxxxxxx>
---
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
--
Thanks,
Qi
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