[PATCH 4.19 231/276] x86/mce: Fix machine_check_poll() tests for error types

[PATCH 4.19 231/276] x86/mce: Fix machine_check_poll() tests for error types

[Greg Kroah-Hartman]

[ Upstream commit f19501aa07f18268ab14f458b51c1c6b7f72a134 ]

There has been a lurking "TBD" in the machine check poll routine ever
since it was first split out from the machine check handler. The
potential issue is that the poll routine may have just begun a read from
the STATUS register in a machine check bank when the hardware logs an
error in that bank and signals a machine check.

That race used to be pretty small back when machine checks were
broadcast, but the addition of local machine check means that the poll
code could continue running and clear the error from the bank before the
local machine check handler on another CPU gets around to reading it.

Fix the code to be sure to only process errors that need to be processed
in the poll code, leaving other logged errors alone for the machine
check handler to find and process.

 [ bp: Massage a bit and flip the "== 0" check to the usual !(..) test. ]

Fixes: b79109c3bbcf ("x86, mce: separate correct machine check poller and fatal exception handler")
Fixes: ed7290d0ee8f ("x86, mce: implement new status bits")
Reported-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Ashok Raj <ashok.raj@intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86-ml <x86@kernel.org>
Cc: Yazen Ghannam <Yazen.Ghannam@amd.com>
Link: https://lkml.kernel.org/r/20190312170938.GA23035@agluck-desk
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/x86/kernel/cpu/mcheck/mce.c | 44 +++++++++++++++++++++++++++-----
 1 file changed, 37 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index f9e7096b1804d..45bd926359f62 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -711,19 +711,49 @@ bool machine_check_poll(enum mcp_flags flags, mce_banks_t *b)
 
 		barrier();
 		m.status = mce_rdmsrl(msr_ops.status(i));
+
+		/* If this entry is not valid, ignore it */
 		if (!(m.status & MCI_STATUS_VAL))
 			continue;
 
 		/*
-		 * Uncorrected or signalled events are handled by the exception
-		 * handler when it is enabled, so don't process those here.
-		 *
-		 * TBD do the same check for MCI_STATUS_EN here?
+		 * If we are logging everything (at CPU online) or this
+		 * is a corrected error, then we must log it.
 		 */
-		if (!(flags & MCP_UC) &&
-		    (m.status & (mca_cfg.ser ? MCI_STATUS_S : MCI_STATUS_UC)))
-			continue;
+		if ((flags & MCP_UC) || !(m.status & MCI_STATUS_UC))
+			goto log_it;
+
+		/*
+		 * Newer Intel systems that support software error
+		 * recovery need to make additional checks. Other
+		 * CPUs should skip over uncorrected errors, but log
+		 * everything else.
+		 */
+		if (!mca_cfg.ser) {
+			if (m.status & MCI_STATUS_UC)
+				continue;
+			goto log_it;
+		}
+
+		/* Log "not enabled" (speculative) errors */
+		if (!(m.status & MCI_STATUS_EN))
+			goto log_it;
+
+		/*
+		 * Log UCNA (SDM: 15.6.3 "UCR Error Classification")
+		 * UC == 1 && PCC == 0 && S == 0
+		 */
+		if (!(m.status & MCI_STATUS_PCC) && !(m.status & MCI_STATUS_S))
+			goto log_it;
+
+		/*
+		 * Skip anything else. Presumption is that our read of this
+		 * bank is racing with a machine check. Leave the log alone
+		 * for do_machine_check() to deal with it.
+		 */
+		continue;
 
+log_it:
 		error_seen = true;
 
 		mce_read_aux(&m, i);
-- 
2.20.1

[PATCH 4.19 233/276] x86/mce: Handle varying MCA bank counts

[Greg Kroah-Hartman]

[ Upstream commit 006c077041dc73b9490fffc4c6af5befe0687110 ]

Linux reads MCG_CAP[Count] to find the number of MCA banks visible to a
CPU. Currently, this number is the same for all CPUs and a warning is
shown if there is a difference. The number of banks is overwritten with
the MCG_CAP[Count] value of each following CPU that boots.

According to the Intel SDM and AMD APM, the MCG_CAP[Count] value gives
the number of banks that are available to a "processor implementation".
The AMD BKDGs/PPRs further clarify that this value is per core. This
value has historically been the same for every core in the system, but
that is not an architectural requirement.

Future AMD systems may have different MCG_CAP[Count] values per core,
so the assumption that all CPUs will have the same MCG_CAP[Count] value
will no longer be valid.

Also, the first CPU to boot will allocate the struct mce_banks[] array
using the number of banks based on its MCG_CAP[Count] value. The machine
check handler and other functions use the global number of banks to
iterate and index into the mce_banks[] array. So it's possible to use an
out-of-bounds index on an asymmetric system where a following CPU sees a
MCG_CAP[Count] value greater than its predecessors.

Thus, allocate the mce_banks[] array to the maximum number of banks.
This will avoid the potential out-of-bounds index since the value of
mca_cfg.banks is capped to MAX_NR_BANKS.

Set the value of mca_cfg.banks equal to the max of the previous value
and the value for the current CPU. This way mca_cfg.banks will always
represent the max number of banks detected on any CPU in the system.

This will ensure that all CPUs will access all the banks that are
visible to them. A CPU that can access fewer than the max number of
banks will find the registers of the extra banks to be read-as-zero.

Furthermore, print the resulting number of MCA banks in use. Do this in
mcheck_late_init() so that the final value is printed after all CPUs
have been initialized.

Finally, get bank count from target CPU when doing injection with mce-inject
module.

 [ bp: Remove out-of-bounds example, passify and cleanup commit message. ]

Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
Cc: Pu Wen <puwen@hygon.cn>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20180727214009.78289-1-Yazen.Ghannam@amd.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/x86/kernel/cpu/mcheck/mce-inject.c | 14 +++++++-------
 arch/x86/kernel/cpu/mcheck/mce.c        | 22 +++++++---------------
 2 files changed, 14 insertions(+), 22 deletions(-)

diff --git a/arch/x86/kernel/cpu/mcheck/mce-inject.c b/arch/x86/kernel/cpu/mcheck/mce-inject.c
index c805a06e14c38..ff1c00b695aed 100644
--- a/arch/x86/kernel/cpu/mcheck/mce-inject.c
+++ b/arch/x86/kernel/cpu/mcheck/mce-inject.c
@@ -46,8 +46,6 @@
 static struct mce i_mce;
 static struct dentry *dfs_inj;
 
-static u8 n_banks;
-
 #define MAX_FLAG_OPT_SIZE	4
 #define NBCFG			0x44
 
@@ -567,9 +565,15 @@ static void do_inject(void)
 static int inj_bank_set(void *data, u64 val)
 {
 	struct mce *m = (struct mce *)data;
+	u8 n_banks;
+	u64 cap;
+
+	/* Get bank count on target CPU so we can handle non-uniform values. */
+	rdmsrl_on_cpu(m->extcpu, MSR_IA32_MCG_CAP, &cap);
+	n_banks = cap & MCG_BANKCNT_MASK;
 
 	if (val >= n_banks) {
-		pr_err("Non-existent MCE bank: %llu\n", val);
+		pr_err("MCA bank %llu non-existent on CPU%d\n", val, m->extcpu);
 		return -EINVAL;
 	}
 
@@ -659,10 +663,6 @@ static struct dfs_node {
 static int __init debugfs_init(void)
 {
 	unsigned int i;
-	u64 cap;
-
-	rdmsrl(MSR_IA32_MCG_CAP, cap);
-	n_banks = cap & MCG_BANKCNT_MASK;
 
 	dfs_inj = debugfs_create_dir("mce-inject", NULL);
 	if (!dfs_inj)
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 45bd926359f62..fee118b3b69fd 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -1480,13 +1480,12 @@ EXPORT_SYMBOL_GPL(mce_notify_irq);
 static int __mcheck_cpu_mce_banks_init(void)
 {
 	int i;
-	u8 num_banks = mca_cfg.banks;
 
-	mce_banks = kcalloc(num_banks, sizeof(struct mce_bank), GFP_KERNEL);
+	mce_banks = kcalloc(MAX_NR_BANKS, sizeof(struct mce_bank), GFP_KERNEL);
 	if (!mce_banks)
 		return -ENOMEM;
 
-	for (i = 0; i < num_banks; i++) {
+	for (i = 0; i < MAX_NR_BANKS; i++) {
 		struct mce_bank *b = &mce_banks[i];
 
 		b->ctl = -1ULL;
@@ -1500,28 +1499,19 @@ static int __mcheck_cpu_mce_banks_init(void)
  */
 static int __mcheck_cpu_cap_init(void)
 {
-	unsigned b;
 	u64 cap;
+	u8 b;
 
 	rdmsrl(MSR_IA32_MCG_CAP, cap);
 
 	b = cap & MCG_BANKCNT_MASK;
-	if (!mca_cfg.banks)
-		pr_info("CPU supports %d MCE banks\n", b);
-
-	if (b > MAX_NR_BANKS) {
-		pr_warn("Using only %u machine check banks out of %u\n",
-			MAX_NR_BANKS, b);
+	if (WARN_ON_ONCE(b > MAX_NR_BANKS))
 		b = MAX_NR_BANKS;
-	}
 
-	/* Don't support asymmetric configurations today */
-	WARN_ON(mca_cfg.banks != 0 && b != mca_cfg.banks);
-	mca_cfg.banks = b;
+	mca_cfg.banks = max(mca_cfg.banks, b);
 
 	if (!mce_banks) {
 		int err = __mcheck_cpu_mce_banks_init();
-
 		if (err)
 			return err;
 	}
@@ -2503,6 +2493,8 @@ EXPORT_SYMBOL_GPL(mcsafe_key);
 
 static int __init mcheck_late_init(void)
 {
+	pr_info("Using %d MCE banks\n", mca_cfg.banks);
+
 	if (mca_cfg.recovery)
 		static_branch_inc(&mcsafe_key);
 
-- 
2.20.1