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From:   Smita Koralahalli <Smita.KoralahalliChannabasappa@amd.com>
To:     <x86@kernel.org>, <linux-edac@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>
CC:     Tony Luck <tony.luck@intel.com>, "H . Peter Anvin" <hpa@zytor.com>,
        <yazen.ghannam@amd.com>, <Smita.KoralahalliChannabasappa@amd.com>
Subject: [PATCH v2 1/5] x86/mce/inject: Check if a bank is unpopulated before error injection
Date:   Tue, 19 Oct 2021 18:36:37 -0500
Message-ID: <20211019233641.140275-2-Smita.KoralahalliChannabasappa@amd.com>
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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@amd.com>
---
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(-)

diff --git a/arch/x86/kernel/cpu/mce/inject.c b/arch/x86/kernel/cpu/mce/inject.c
index 0bfc14041bbb..601efd104bb4 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)			\
@@ -89,13 +88,11 @@ MCE_INJECT_GET(status);
 MCE_INJECT_GET(misc);
 MCE_INJECT_GET(addr);
 MCE_INJECT_GET(synd);
-MCE_INJECT_GET(ipid);
 
 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");
-DEFINE_SIMPLE_ATTRIBUTE(ipid_fops, inj_ipid_get, inj_ipid_set, "%llx\n");
 
 static void setup_inj_struct(struct mce *m)
 {
@@ -577,6 +574,25 @@ static int inj_bank_set(void *data, u64 val)
 	}
 
 	m->bank = val;
+
+	/*
+	 * Read IPID value to determine if a bank is unpopulated on the target
+	 * CPU.
+	 */
+	if (cpu_feature_enabled(X86_FEATURE_SMCA)) {
+
+		/* Check for user provided IPID value on a sw injection. */
+		if (!m->ipid) {
+			rdmsrl_on_cpu(m->extcpu, MSR_AMD64_SMCA_MCx_IPID(val),
+				      &m->ipid);
+			if (!m->ipid) {
+				pr_err("Cannot set IPID - bank %llu unpopulated\n",
+					val);
+				return -ENODEV;
+			}
+		}
+	}
+
 	do_inject();
 
 	/* Reset injection struct */
@@ -589,6 +605,23 @@ MCE_INJECT_GET(bank);
 
 DEFINE_SIMPLE_ATTRIBUTE(bank_fops, inj_bank_get, inj_bank_set, "%llu\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 (val && inj_type == SW_INJ)
+			m->ipid = val;
+	}
+
+	return 0;
+}
+
+MCE_INJECT_GET(ipid);
+
+DEFINE_SIMPLE_ATTRIBUTE(ipid_fops, inj_ipid_get, inj_ipid_set, "%llx\n");
+
 static const char readme_msg[] =
 "Description of the files and their usages:\n"
 "\n"
-- 
2.17.1