Re: [PATCH v2 1/5] x86/mce/inject: Check if a bank is unpopulated before error injection
From: Koralahalli Channabasappa, Smita
Date: Mon Oct 25 2021 - 13:10:08 EST
On 10/25/21 8:56 AM, Borislav Petkov wrote:
On Tue, Oct 19, 2021 at 06:36:37PM -0500, Smita Koralahalli wrote:
The MCA_IPID register uniquely identifies a bank's type on Scalable MCA
(SMCA) systems. When an MCA bank is not populated, the MCA_IPID register
will read as zero and writes to it will be ignored.
On a "hw" error injection check the value of this register before trying
to inject the error.
Do not impose any limitation on a "sw" injection and allow the user to
test out all the decoding paths without relying on the available hardware,
as its purpose is to just test the code.
Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@xxxxxxx>
---
v2:
simulate -> inject.
Corrected according to kernel commenting style.
boot_cpu_has() -> cpu_feature_enabled().
Error simulation not possible: Bank %llu unpopulated ->
Cannot set IPID - bank %llu unpopulated.
Used user provided IPID value on sw injection without checking
underlying hardware and defined it under inj_ipid_set().
---
arch/x86/kernel/cpu/mce/inject.c | 39 +++++++++++++++++++++++++++++---
1 file changed, 36 insertions(+), 3 deletions(-)
So I gave it a critical look and did some modifications, see below.
Looking at those IPID MSRs - they're all read-only, which means for !sw
injection, all the module can do is check whether they're 0 - and fail
injection in that case - and do the injection otherwise.
Ok?
Yes, this looks more clearer. Thank you.
---
From: Smita Koralahalli <Smita.KoralahalliChannabasappa@xxxxxxx>
Date: Tue, 19 Oct 2021 18:36:37 -0500
Subject: [PATCH] x86/mce/inject: Check if a bank is populated before error
injection
The MCA_IPID register uniquely identifies a bank's type on Scalable MCA
(SMCA) systems. When an MCA bank is not populated, the MCA_IPID register
will read as zero and writes to it will be ignored.
On a hw-type error injection (injection which writes the actual MCA
registers in an attempt to cause a real MCE) check the value of this
register before trying to inject the error.
Do not impose any limitation on a sw-type injection (software-only
injection) and allow the user to test out all the decoding paths without
relying on the available hardware, as its purpose is to just test the
code.
[ bp: Heavily massage. ]
Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@xxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Link: https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flkml.kernel.org%2Fr%2F20211019233641.140275-2-Smita.KoralahalliChannabasappa%40amd.com&data=04%7C01%7CSmita.KoralahalliChannabasappa%40amd.com%7C6da4cbaab660413d27a208d997bf48f1%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637707670099990329%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=Jpecn9lg2XxdqhbLpMIxuSh%2BRA3eafMReXmdLI3SkfM%3D&reserved=0
---
arch/x86/kernel/cpu/mce/inject.c | 42 +++++++++++++++++++++++++++++++-
1 file changed, 41 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/cpu/mce/inject.c b/arch/x86/kernel/cpu/mce/inject.c
index 0bfc14041bbb..3333ae7886bd 100644
--- a/arch/x86/kernel/cpu/mce/inject.c
+++ b/arch/x86/kernel/cpu/mce/inject.c
@@ -74,7 +74,6 @@ MCE_INJECT_SET(status);
MCE_INJECT_SET(misc);
MCE_INJECT_SET(addr);
MCE_INJECT_SET(synd);
-MCE_INJECT_SET(ipid);
#define MCE_INJECT_GET(reg) \
static int inj_##reg##_get(void *data, u64 *val) \
@@ -95,6 +94,20 @@ DEFINE_SIMPLE_ATTRIBUTE(status_fops, inj_status_get, inj_status_set, "%llx\n");
DEFINE_SIMPLE_ATTRIBUTE(misc_fops, inj_misc_get, inj_misc_set, "%llx\n");
DEFINE_SIMPLE_ATTRIBUTE(addr_fops, inj_addr_get, inj_addr_set, "%llx\n");
DEFINE_SIMPLE_ATTRIBUTE(synd_fops, inj_synd_get, inj_synd_set, "%llx\n");
+
+/* Use the user provided IPID value on a sw injection. */
+static int inj_ipid_set(void *data, u64 val)
+{
+ struct mce *m = (struct mce *)data;
+
+ if (cpu_feature_enabled(X86_FEATURE_SMCA)) {
+ if (inj_type == SW_INJ)
+ m->ipid = val;
+ }
+
+ return 0;
+}
+
DEFINE_SIMPLE_ATTRIBUTE(ipid_fops, inj_ipid_get, inj_ipid_set, "%llx\n");
static void setup_inj_struct(struct mce *m)
@@ -577,6 +590,33 @@ static int inj_bank_set(void *data, u64 val)
}
m->bank = val;
+
+ /*
+ * sw-only injection allows to write arbitrary values into the MCA registers
+ * because it tests only the decoding paths.
+ */
+ if (inj_type == SW_INJ)
+ goto inject;
+
+ /*
+ * Read IPID value to determine if a bank is populated on the target
+ * CPU.
+ */
+ if (cpu_feature_enabled(X86_FEATURE_SMCA)) {
+ u64 ipid;
+
+ if (rdmsrl_on_cpu(m->extcpu, MSR_AMD64_SMCA_MCx_IPID(val), &ipid)) {
+ pr_err("Error reading IPID on CPU%d\n", m->extcpu);
+ return -EINVAL;
+ }
+
+ if (!ipid) {
+ pr_err("Cannot inject into bank %llu - it is unpopulated\n", val);
+ return -ENODEV;
+ }
+ }
+
+inject:
do_inject();
/* Reset injection struct */