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authorPaul Mackerras <paulus@ozlabs.org>2018-01-17 20:51:13 +1100
committerMichael Ellerman <mpe@ellerman.id.au>2018-01-18 15:31:25 +1100
commitd075745d893c78730e4a3b7a60fca23c2f764081 (patch)
tree5503d7e4b87f2e9cdfe42f7ab2407d7294667714
parent7f1c410da59090f9bb2300efebbc3b717594d64c (diff)
downloadlinux-d075745d893c78730e4a3b7a60fca23c2f764081.tar.bz2
KVM: PPC: Book3S HV: Improve handling of debug-trigger HMIs on POWER9
Hypervisor maintenance interrupts (HMIs) are generated by various causes, signalled by bits in the hypervisor maintenance exception register (HMER). In most cases calling OPAL to handle the interrupt is the correct thing to do, but the "debug trigger" HMIs signalled by PPC bit 17 (bit 46) of HMER are used to invoke software workarounds for hardware bugs, and OPAL does not have any code to handle this cause. The debug trigger HMI is used in POWER9 DD2.0 and DD2.1 chips to work around a hardware bug in executing vector load instructions to cache inhibited memory. In POWER9 DD2.2 chips, it is generated when conditions are detected relating to threads being in TM (transactional memory) suspended mode when the core SMT configuration needs to be reconfigured. The kernel currently has code to detect the vector CI load condition, but only when the HMI occurs in the host, not when it occurs in a guest. If a HMI occurs in the guest, it is always passed to OPAL, and then we always re-sync the timebase, because the HMI cause might have been a timebase error, for which OPAL would re-sync the timebase, thus removing the timebase offset which KVM applied for the guest. Since we don't know what OPAL did, we don't know whether to subtract the timebase offset from the timebase, so instead we re-sync the timebase. This adds code to determine explicitly what the cause of a debug trigger HMI will be. This is based on a new device-tree property under the CPU nodes called ibm,hmi-special-triggers, if it is present, or otherwise based on the PVR (processor version register). The handling of debug trigger HMIs is pulled out into a separate function which can be called from the KVM guest exit code. If this function handles and clears the HMI, and no other HMI causes remain, then we skip calling OPAL and we proceed to subtract the guest timebase offset from the timebase. The overall handling for HMIs that occur in the host (i.e. not in a KVM guest) is largely unchanged, except that we now don't set the flag for the vector CI load workaround on DD2.2 processors. This also removes a BUG_ON in the KVM code. BUG_ON is generally not useful in KVM guest entry/exit code since it is difficult to handle the resulting trap gracefully. Signed-off-by: Paul Mackerras <paulus@ozlabs.org> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
-rw-r--r--arch/powerpc/include/asm/hmi.h4
-rw-r--r--arch/powerpc/include/asm/reg.h5
-rw-r--r--arch/powerpc/kernel/mce.c142
-rw-r--r--arch/powerpc/kvm/book3s_hv_ras.c8
-rw-r--r--arch/powerpc/kvm/book3s_hv_rmhandlers.S9
5 files changed, 131 insertions, 37 deletions
diff --git a/arch/powerpc/include/asm/hmi.h b/arch/powerpc/include/asm/hmi.h
index 85b7a1a21e22..9c14f7b5c46c 100644
--- a/arch/powerpc/include/asm/hmi.h
+++ b/arch/powerpc/include/asm/hmi.h
@@ -42,4 +42,8 @@ extern void wait_for_tb_resync(void);
static inline void wait_for_subcore_guest_exit(void) { }
static inline void wait_for_tb_resync(void) { }
#endif
+
+struct pt_regs;
+extern long hmi_handle_debugtrig(struct pt_regs *regs);
+
#endif /* __ASM_PPC64_HMI_H__ */
diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index b779f3ccd412..14e41b843952 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -432,8 +432,9 @@
#define SPRN_LPID 0x13F /* Logical Partition Identifier */
#endif
#define LPID_RSVD 0x3ff /* Reserved LPID for partn switching */
-#define SPRN_HMER 0x150 /* Hardware m? error recovery */
-#define SPRN_HMEER 0x151 /* Hardware m? enable error recovery */
+#define SPRN_HMER 0x150 /* Hypervisor maintenance exception reg */
+#define HMER_DEBUG_TRIG (1ul << (63 - 17)) /* Debug trigger */
+#define SPRN_HMEER 0x151 /* Hyp maintenance exception enable reg */
#define SPRN_PCR 0x152 /* Processor compatibility register */
#define PCR_VEC_DIS (1ul << (63-0)) /* Vec. disable (bit NA since POWER8) */
#define PCR_VSX_DIS (1ul << (63-1)) /* VSX disable (bit NA since POWER8) */
diff --git a/arch/powerpc/kernel/mce.c b/arch/powerpc/kernel/mce.c
index 742e4658c5dc..d2fecaec4fec 100644
--- a/arch/powerpc/kernel/mce.c
+++ b/arch/powerpc/kernel/mce.c
@@ -495,37 +495,123 @@ long machine_check_early(struct pt_regs *regs)
return handled;
}
-long hmi_exception_realmode(struct pt_regs *regs)
+/* Possible meanings for HMER_DEBUG_TRIG bit being set on POWER9 */
+static enum {
+ DTRIG_UNKNOWN,
+ DTRIG_VECTOR_CI, /* need to emulate vector CI load instr */
+ DTRIG_SUSPEND_ESCAPE, /* need to escape from TM suspend mode */
+} hmer_debug_trig_function;
+
+static int init_debug_trig_function(void)
{
- __this_cpu_inc(irq_stat.hmi_exceptions);
-
-#ifdef CONFIG_PPC_BOOK3S_64
- /* Workaround for P9 vector CI loads (see p9_hmi_special_emu) */
- if (pvr_version_is(PVR_POWER9)) {
- unsigned long hmer = mfspr(SPRN_HMER);
-
- /* Do we have the debug bit set */
- if (hmer & PPC_BIT(17)) {
- hmer &= ~PPC_BIT(17);
- mtspr(SPRN_HMER, hmer);
-
- /*
- * Now to avoid problems with soft-disable we
- * only do the emulation if we are coming from
- * user space
- */
- if (user_mode(regs))
- local_paca->hmi_p9_special_emu = 1;
-
- /*
- * Don't bother going to OPAL if that's the
- * only relevant bit.
- */
- if (!(hmer & mfspr(SPRN_HMEER)))
- return local_paca->hmi_p9_special_emu;
+ int pvr;
+ struct device_node *cpun;
+ struct property *prop = NULL;
+ const char *str;
+
+ /* First look in the device tree */
+ preempt_disable();
+ cpun = of_get_cpu_node(smp_processor_id(), NULL);
+ if (cpun) {
+ of_property_for_each_string(cpun, "ibm,hmi-special-triggers",
+ prop, str) {
+ if (strcmp(str, "bit17-vector-ci-load") == 0)
+ hmer_debug_trig_function = DTRIG_VECTOR_CI;
+ else if (strcmp(str, "bit17-tm-suspend-escape") == 0)
+ hmer_debug_trig_function = DTRIG_SUSPEND_ESCAPE;
}
+ of_node_put(cpun);
+ }
+ preempt_enable();
+
+ /* If we found the property, don't look at PVR */
+ if (prop)
+ goto out;
+
+ pvr = mfspr(SPRN_PVR);
+ /* Check for POWER9 Nimbus (scale-out) */
+ if ((PVR_VER(pvr) == PVR_POWER9) && (pvr & 0xe000) == 0) {
+ /* DD2.2 and later */
+ if ((pvr & 0xfff) >= 0x202)
+ hmer_debug_trig_function = DTRIG_SUSPEND_ESCAPE;
+ /* DD2.0 and DD2.1 - used for vector CI load emulation */
+ else if ((pvr & 0xfff) >= 0x200)
+ hmer_debug_trig_function = DTRIG_VECTOR_CI;
+ }
+
+ out:
+ switch (hmer_debug_trig_function) {
+ case DTRIG_VECTOR_CI:
+ pr_debug("HMI debug trigger used for vector CI load\n");
+ break;
+ case DTRIG_SUSPEND_ESCAPE:
+ pr_debug("HMI debug trigger used for TM suspend escape\n");
+ break;
+ default:
+ break;
}
-#endif /* CONFIG_PPC_BOOK3S_64 */
+ return 0;
+}
+__initcall(init_debug_trig_function);
+
+/*
+ * Handle HMIs that occur as a result of a debug trigger.
+ * Return values:
+ * -1 means this is not a HMI cause that we know about
+ * 0 means no further handling is required
+ * 1 means further handling is required
+ */
+long hmi_handle_debugtrig(struct pt_regs *regs)
+{
+ unsigned long hmer = mfspr(SPRN_HMER);
+ long ret = 0;
+
+ /* HMER_DEBUG_TRIG bit is used for various workarounds on P9 */
+ if (!((hmer & HMER_DEBUG_TRIG)
+ && hmer_debug_trig_function != DTRIG_UNKNOWN))
+ return -1;
+
+ hmer &= ~HMER_DEBUG_TRIG;
+ /* HMER is a write-AND register */
+ mtspr(SPRN_HMER, ~HMER_DEBUG_TRIG);
+
+ switch (hmer_debug_trig_function) {
+ case DTRIG_VECTOR_CI:
+ /*
+ * Now to avoid problems with soft-disable we
+ * only do the emulation if we are coming from
+ * host user space
+ */
+ if (regs && user_mode(regs))
+ ret = local_paca->hmi_p9_special_emu = 1;
+
+ break;
+
+ default:
+ break;
+ }
+
+ /*
+ * See if any other HMI causes remain to be handled
+ */
+ if (hmer & mfspr(SPRN_HMEER))
+ return -1;
+
+ return ret;
+}
+
+/*
+ * Return values:
+ */
+long hmi_exception_realmode(struct pt_regs *regs)
+{
+ int ret;
+
+ __this_cpu_inc(irq_stat.hmi_exceptions);
+
+ ret = hmi_handle_debugtrig(regs);
+ if (ret >= 0)
+ return ret;
wait_for_subcore_guest_exit();
diff --git a/arch/powerpc/kvm/book3s_hv_ras.c b/arch/powerpc/kvm/book3s_hv_ras.c
index c356f9a40b24..c296343d0dcc 100644
--- a/arch/powerpc/kvm/book3s_hv_ras.c
+++ b/arch/powerpc/kvm/book3s_hv_ras.c
@@ -268,17 +268,19 @@ static void kvmppc_tb_resync_done(void)
* secondary threads to proceed.
* - All secondary threads will eventually call opal hmi handler on
* their exit path.
+ *
+ * Returns 1 if the timebase offset should be applied, 0 if not.
*/
long kvmppc_realmode_hmi_handler(void)
{
- int ptid = local_paca->kvm_hstate.ptid;
bool resync_req;
- /* This is only called on primary thread. */
- BUG_ON(ptid != 0);
__this_cpu_inc(irq_stat.hmi_exceptions);
+ if (hmi_handle_debugtrig(NULL) >= 0)
+ return 1;
+
/*
* By now primary thread has already completed guest->host
* partition switch but haven't signaled secondaries yet.
diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index 2659844784b8..bd0b623335af 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -1909,16 +1909,17 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
bne 27f
bl kvmppc_realmode_hmi_handler
nop
+ cmpdi r3, 0
li r12, BOOK3S_INTERRUPT_HMI
/*
- * At this point kvmppc_realmode_hmi_handler would have resync-ed
- * the TB. Hence it is not required to subtract guest timebase
- * offset from timebase. So, skip it.
+ * At this point kvmppc_realmode_hmi_handler may have resync-ed
+ * the TB, and if it has, we must not subtract the guest timebase
+ * offset from the timebase. So, skip it.
*
* Also, do not call kvmppc_subcore_exit_guest() because it has
* been invoked as part of kvmppc_realmode_hmi_handler().
*/
- b 30f
+ beq 30f
27:
/* Subtract timebase offset from timebase */