powerpc/book3s: Decode and save machine check event.

Now that we handle machine check in linux, the MCE decoding should also
take place in linux host. This info is crucial to log before we go down
in case we can not handle the machine check errors. This patch decodes
and populates a machine check event which contain high level meaning full
MCE information.

We do this in real mode C code with ME bit on. The MCE information is still
available on emergency stack (in pt_regs structure format). Even if we take
another exception at this point the MCE early handler will allocate a new
stack frame on top of current one. So when we return back here we still have
our MCE information safe on current stack.

We use per cpu buffer to save high level MCE information. Each per cpu buffer
is an array of machine check event structure indexed by per cpu counter
mce_nest_count. The mce_nest_count is incremented every time we enter
machine check early handler in real mode to get the current free slot
(index = mce_nest_count - 1). The mce_nest_count is decremented once the
MCE info is consumed by virtual mode machine exception handler.

This patch provides save_mce_event(), get_mce_event() and release_mce_event()
generic routines that can be used by machine check handlers to populate and
retrieve the event. The routine release_mce_event() will free the event slot so
that it can be reused. Caller can invoke get_mce_event() with a release flag
either to release the event slot immediately OR keep it so that it can be
fetched again. The event slot can be also released anytime by invoking
release_mce_event().

This patch also updates kvm code to invoke get_mce_event to retrieve generic
mce event rather than paca->opal_mce_evt.

The KVM code always calls get_mce_event() with release flags set to false so
that event is available for linus host machine

If machine check occurs while we are in guest, KVM tries to handle the error.
If KVM is able to handle MC error successfully, it enters the guest and
delivers the machine check to guest. If KVM is not able to handle MC error, it
exists the guest and passes the control to linux host machine check handler
which then logs MC event and decides how to handle it in linux host. In failure
case, KVM needs to make sure that the MC event is available for linux host to
consume. Hence KVM always calls get_mce_event() with release flags set to false
and later it invokes release_mce_event() only if it succeeds to handle error.

Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 108 insertions, 8 deletions

diff --git a/arch/powerpc/kernel/mce_power.c b/arch/powerpc/kernel/mce_power.c
index 60a217f11275..b36e777a734f 100644
--- a/arch/powerpc/kernel/mce_power.c
+++ b/arch/powerpc/kernel/mce_power.c
@@ -133,22 +133,116 @@ static long mce_handle_ierror_p7(uint64_t srr1)
 	return handled;
 }
 
+static void mce_get_common_ierror(struct mce_error_info *mce_err, uint64_t srr1)
+{
+	switch (P7_SRR1_MC_IFETCH(srr1)) {
+	case P7_SRR1_MC_IFETCH_SLB_PARITY:
+		mce_err->error_type = MCE_ERROR_TYPE_SLB;
+		mce_err->u.slb_error_type = MCE_SLB_ERROR_PARITY;
+		break;
+	case P7_SRR1_MC_IFETCH_SLB_MULTIHIT:
+		mce_err->error_type = MCE_ERROR_TYPE_SLB;
+		mce_err->u.slb_error_type = MCE_SLB_ERROR_MULTIHIT;
+		break;
+	case P7_SRR1_MC_IFETCH_TLB_MULTIHIT:
+		mce_err->error_type = MCE_ERROR_TYPE_TLB;
+		mce_err->u.tlb_error_type = MCE_TLB_ERROR_MULTIHIT;
+		break;
+	case P7_SRR1_MC_IFETCH_UE:
+	case P7_SRR1_MC_IFETCH_UE_IFU_INTERNAL:
+		mce_err->error_type = MCE_ERROR_TYPE_UE;
+		mce_err->u.ue_error_type = MCE_UE_ERROR_IFETCH;
+		break;
+	case P7_SRR1_MC_IFETCH_UE_TLB_RELOAD:
+		mce_err->error_type = MCE_ERROR_TYPE_UE;
+		mce_err->u.ue_error_type =
+				MCE_UE_ERROR_PAGE_TABLE_WALK_IFETCH;
+		break;
+	}
+}
+
+static void mce_get_ierror_p7(struct mce_error_info *mce_err, uint64_t srr1)
+{
+	mce_get_common_ierror(mce_err, srr1);
+	if (P7_SRR1_MC_IFETCH(srr1) == P7_SRR1_MC_IFETCH_SLB_BOTH) {
+		mce_err->error_type = MCE_ERROR_TYPE_SLB;
+		mce_err->u.slb_error_type = MCE_SLB_ERROR_INDETERMINATE;
+	}
+}
+
+static void mce_get_derror_p7(struct mce_error_info *mce_err, uint64_t dsisr)
+{
+	if (dsisr & P7_DSISR_MC_UE) {
+		mce_err->error_type = MCE_ERROR_TYPE_UE;
+		mce_err->u.ue_error_type = MCE_UE_ERROR_LOAD_STORE;
+	} else if (dsisr & P7_DSISR_MC_UE_TABLEWALK) {
+		mce_err->error_type = MCE_ERROR_TYPE_UE;
+		mce_err->u.ue_error_type =
+				MCE_UE_ERROR_PAGE_TABLE_WALK_LOAD_STORE;
+	} else if (dsisr & P7_DSISR_MC_ERAT_MULTIHIT) {
+		mce_err->error_type = MCE_ERROR_TYPE_ERAT;
+		mce_err->u.erat_error_type = MCE_ERAT_ERROR_MULTIHIT;
+	} else if (dsisr & P7_DSISR_MC_SLB_MULTIHIT) {
+		mce_err->error_type = MCE_ERROR_TYPE_SLB;
+		mce_err->u.slb_error_type = MCE_SLB_ERROR_MULTIHIT;
+	} else if (dsisr & P7_DSISR_MC_SLB_PARITY_MFSLB) {
+		mce_err->error_type = MCE_ERROR_TYPE_SLB;
+		mce_err->u.slb_error_type = MCE_SLB_ERROR_PARITY;
+	} else if (dsisr & P7_DSISR_MC_TLB_MULTIHIT_MFTLB) {
+		mce_err->error_type = MCE_ERROR_TYPE_TLB;
+		mce_err->u.tlb_error_type = MCE_TLB_ERROR_MULTIHIT;
+	} else if (dsisr & P7_DSISR_MC_SLB_MULTIHIT_PARITY) {
+		mce_err->error_type = MCE_ERROR_TYPE_SLB;
+		mce_err->u.slb_error_type = MCE_SLB_ERROR_INDETERMINATE;
+	}
+}
+
 long __machine_check_early_realmode_p7(struct pt_regs *regs)
 {
-	uint64_t srr1;
+	uint64_t srr1, addr;
 	long handled = 1;
+	struct mce_error_info mce_error_info = { 0 };
 
 	srr1 = regs->msr;
 
-	if (P7_SRR1_MC_LOADSTORE(srr1))
+	/*
+	 * Handle memory errors depending whether this was a load/store or
+	 * ifetch exception. Also, populate the mce error_type and
+	 * type-specific error_type from either SRR1 or DSISR, depending
+	 * whether this was a load/store or ifetch exception
+	 */
+	if (P7_SRR1_MC_LOADSTORE(srr1)) {
 		handled = mce_handle_derror_p7(regs->dsisr);
-	else
+		mce_get_derror_p7(&mce_error_info, regs->dsisr);
+		addr = regs->dar;
+	} else {
 		handled = mce_handle_ierror_p7(srr1);
+		mce_get_ierror_p7(&mce_error_info, srr1);
+		addr = regs->nip;
+	}
 
-	/* TODO: Decode machine check reason. */
+	save_mce_event(regs, handled, &mce_error_info, addr);
 	return handled;
 }
 
+static void mce_get_ierror_p8(struct mce_error_info *mce_err, uint64_t srr1)
+{
+	mce_get_common_ierror(mce_err, srr1);
+	if (P7_SRR1_MC_IFETCH(srr1) == P8_SRR1_MC_IFETCH_ERAT_MULTIHIT) {
+		mce_err->error_type = MCE_ERROR_TYPE_ERAT;
+		mce_err->u.erat_error_type = MCE_ERAT_ERROR_MULTIHIT;
+	}
+}
+
+static void mce_get_derror_p8(struct mce_error_info *mce_err, uint64_t dsisr)
+{
+	mce_get_derror_p7(mce_err, dsisr);
+	if (dsisr & P8_DSISR_MC_ERAT_MULTIHIT_SEC) {
+		mce_err->error_type = MCE_ERROR_TYPE_ERAT;
+		mce_err->u.erat_error_type = MCE_ERAT_ERROR_MULTIHIT;
+	}
+}
+
 static long mce_handle_ierror_p8(uint64_t srr1)
 {
 	long handled = 0;
@@ -169,16 +263,22 @@ static long mce_handle_derror_p8(uint64_t dsisr)
 
 long __machine_check_early_realmode_p8(struct pt_regs *regs)
 {
-	uint64_t srr1;
+	uint64_t srr1, addr;
 	long handled = 1;
+	struct mce_error_info mce_error_info = { 0 };
 
 	srr1 = regs->msr;
 
-	if (P7_SRR1_MC_LOADSTORE(srr1))
+	if (P7_SRR1_MC_LOADSTORE(srr1)) {
 		handled = mce_handle_derror_p8(regs->dsisr);
-	else
+		mce_get_derror_p8(&mce_error_info, regs->dsisr);
+		addr = regs->dar;
+	} else {
 		handled = mce_handle_ierror_p8(srr1);
+		mce_get_ierror_p8(&mce_error_info, srr1);
+		addr = regs->nip;
+	}
 
-	/* TODO: Decode machine check reason. */
+	save_mce_event(regs, handled, &mce_error_info, addr);
 	return handled;
 }