[PATCH 1/5] KVM: PPC: Book3S HV: Handle guest-caused machine checks on POWER7 without panicking

Paul Mackerras
2012-11-22T09:25:55Z

Currently, if a machine check interrupt happens while we are in the
guest, we exit the guest and call the host's machine check handler,
which tends to cause the host to panic. Some machine checks can be
triggered by the guest; for example, if the guest creates two entries
in the SLB that map the same effective address, and then accesses that
effective address, the CPU will take a machine check interrupt.

To handle this better, we firstly don't call the host's machine check
handler for machine checks that happen inside the guest. Instead we
call a new function, kvmppc_realmode_machine_check(), while still in
real mode before exiting the guest. On POWER7, it handles the cases
that the guest can trigger, either by flushing and reloading the SLB,
or by flushing the TLB, and then it delivers the machine check interrupt
to the guest. (On PPC970 we currently just exit the guest and leave it
up to kvmppc_handle_exit() to handle the condition, which it doesn't,
so the situation is no better -- but no worse -- on PPC970 now.)

Signed-off-by: Paul Mackerras <paulus@samba.org>
---
arch/powerpc/kvm/Makefile | 1 +
arch/powerpc/kvm/book3s_hv_ras.c | 115 +++++++++++++++++++++++++++++++
arch/powerpc/kvm/book3s_hv_rmhandlers.S | 61 +++++++++-------
3 files changed, 153 insertions(+), 24 deletions(-)
create mode 100644 arch/powerpc/kvm/book3s_hv_ras.c

diff --git a/arch/powerpc/kvm/Makefile b/arch/powerpc/kvm/Makefile
index cd89658..1e473d4 100644
--- a/arch/powerpc/kvm/Makefile
+++ b/arch/powerpc/kvm/Makefile
@@ -73,6 +73,7 @@ kvm-book3s_64-builtin-objs-$(CONFIG_KVM_BOOK3S_64_HV) := \
book3s_hv_rmhandlers.o \
book3s_hv_rm_mmu.o \
book3s_64_vio_hv.o \
+ book3s_hv_ras.o \
book3s_hv_builtin.o

kvm-book3s_64-module-objs := \
diff --git a/arch/powerpc/kvm/book3s_hv_ras.c b/arch/powerpc/kvm/book3s_hv_ras.c
new file mode 100644
index 0000000..2646d07
--- /dev/null
+++ b/arch/powerpc/kvm/book3s_hv_ras.c
@@ -0,0 +1,115 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License, version 2, as
+ * published by the Free Software Foundation.
+ *
+ * Copyright 2012 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
+ */
+
+#include <linux/types.h>
+#include <linux/string.h>
+#include <linux/kvm.h>
+#include <linux/kvm_host.h>
+
+/* SRR1 bits for machine check on POWER7 */
+#define SRR1_MC_LDSTERR (1ul << (63-42))
+#define SRR1_MC_IFETCH_SH (63-45)
+#define SRR1_MC_IFETCH_MASK 0x7
+#define SRR1_MC_IFETCH_SLBPAR 2 /* SLB parity error */
+#define SRR1_MC_IFETCH_SLBMULTI 3 /* SLB multi-hit */
+#define SRR1_MC_IFETCH_SLBPARMULTI 4 /* SLB parity + multi-hit */
+#define SRR1_MC_IFETCH_TLBMULTI 5 /* I-TLB multi-hit */
+
+/* DSISR bits for machine check on POWER7 */
+#define DSISR_MC_DERAT_MULTI 0x800 /* D-ERAT multi-hit */
+#define DSISR_MC_TLB_MULTI 0x400 /* D-TLB multi-hit */
+#define DSISR_MC_SLB_PARITY 0x100 /* SLB parity error */
+#define DSISR_MC_SLB_MULTI 0x080 /* SLB multi-hit */
+#define DSISR_MC_SLB_PARMULTI 0x040 /* SLB parity + multi-hit */
+
+/* POWER7 SLB flush and reload */
+static void reload_slb(struct kvm_vcpu *vcpu)
+{
+ struct slb_shadow *slb;
+ unsigned long i, n;
+
+ /* First clear out SLB */
+ asm volatile("slbmte %0,%0; slbia" : : "r" (0));
+
+ /* Do they have an SLB shadow buffer registered? */
+ slb = vcpu->arch.slb_shadow.pinned_addr;
+ if (!slb)
+ return;
+
+ /* Sanity check */
+ n = slb->persistent;
+ if (n > SLB_MIN_SIZE)
+ n = SLB_MIN_SIZE;
+ if ((void *) &slb->save_area[n] > vcpu->arch.slb_shadow.pinned_end)
+ return;
+
+ /* Load up the SLB from that */
+ for (i = 0; i < n; ++i) {
+ unsigned long rb = slb->save_area[i].esid;
+ unsigned long rs = slb->save_area[i].vsid;
+
+ rb = (rb & ~0xFFFul) | i; /* insert entry number */
+ asm volatile("slbmte %0,%1" : : "r" (rs), "r" (rb));
+ }
+}
+
+/* POWER7 TLB flush */
+static void flush_tlb_power7(struct kvm_vcpu *vcpu)
+{
+ unsigned long i, rb;
+
+ rb = 0x800; /* IS field = 0b10, flush congruence class */
+ for (i = 0; i < 128; ++i) {
+ asm volatile("tlbiel %0" : : "r" (rb));
+ rb += 0x1000;
+ }
+}
+
+/*
+ * On POWER7, see if we can handle a machine check that occurred inside
+ * the guest in real mode, without switching to the host partition.
+ *
+ * Returns: 0 => exit guest, 1 => deliver machine check to guest
+ */
+static long kvmppc_realmode_mc_power7(struct kvm_vcpu *vcpu)
+{
+ unsigned long srr1 = vcpu->arch.shregs.msr;
+
+ if (srr1 & SRR1_MC_LDSTERR) {
+ /* error on load/store */
+ unsigned long dsisr = vcpu->arch.shregs.dsisr;
+
+ if (dsisr & (DSISR_MC_SLB_PARMULTI | DSISR_MC_SLB_MULTI |
+ DSISR_MC_SLB_PARITY | DSISR_MC_DERAT_MULTI))
+ /* flush and reload SLB; flushes D-ERAT too */
+ reload_slb(vcpu);
+ if (dsisr & DSISR_MC_TLB_MULTI)
+ flush_tlb_power7(vcpu);
+ }
+
+ switch ((srr1 >> SRR1_MC_IFETCH_SH) & SRR1_MC_IFETCH_MASK) {
+ case SRR1_MC_IFETCH_SLBPAR:
+ case SRR1_MC_IFETCH_SLBMULTI:
+ case SRR1_MC_IFETCH_SLBPARMULTI:
+ reload_slb(vcpu);
+ break;
+ case SRR1_MC_IFETCH_TLBMULTI:
+ flush_tlb_power7(vcpu);
+ break;
+ }
+
+ return 1;
+}
+
+long kvmppc_realmode_machine_check(struct kvm_vcpu *vcpu)
+{
+ if (cpu_has_feature(CPU_FTR_ARCH_206))
+ return kvmppc_realmode_mc_power7(vcpu);
+
+ return 0;
+}
diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index 690d112..b31fb4f 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -682,8 +682,7 @@ BEGIN_FTR_SECTION
1:
END_FTR_SECTION_IFSET(CPU_FTR_ARCH_206)

-nohpte_cont:
-hcall_real_cont: /* r9 = vcpu, r12 = trap, r13 = paca */
+guest_exit_cont: /* r9 = vcpu, r12 = trap, r13 = paca */
/* Save DEC */
mfspr r5,SPRN_DEC
mftb r6
@@ -704,6 +703,11 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_206)
std r6, VCPU_FAULT_DAR(r9)
stw r7, VCPU_FAULT_DSISR(r9)

+ /* See if it is a machine check */
+ cmpwi r12, BOOK3S_INTERRUPT_MACHINE_CHECK
+ beq machine_check_realmode
+mc_cont:
+
/* Save guest CTRL register, set runlatch to 1 */
6: mfspr r6,SPRN_CTRLF
stw r6,VCPU_CTRL(r9)
@@ -1114,20 +1118,21 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_201)
isync
23:
/*
- * For external and machine check interrupts, we need
+ * For external interrupts, we need
* to call the Linux handler to process the interrupt.
* We do that by jumping to the interrupt vector address
* which we have in r12. The [h]rfid at the end of the
* handler will return to the book3s_hv_interrupts.S code.
* For other interrupts we do the rfid to get back
- * to the book3s_interrupts.S code here.
+ * to the book3s_hv_interrupts.S code here.
*/
ld r8, HSTATE_VMHANDLER(r13)
ld r7, HSTATE_HOST_MSR(r13)

cmpwi r12, BOOK3S_INTERRUPT_EXTERNAL
+BEGIN_FTR_SECTION
beq 11f
- cmpwi r12, BOOK3S_INTERRUPT_MACHINE_CHECK
+END_FTR_SECTION_IFSET(CPU_FTR_ARCH_206)

/* RFI into the highmem handler, or branch to interrupt handler */
12: mfmsr r6
@@ -1140,11 +1145,8 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_201)
beqctr
RFI

-11:
-BEGIN_FTR_SECTION
- b 12b
-END_FTR_SECTION_IFSET(CPU_FTR_ARCH_201)
- mtspr SPRN_HSRR0, r8
+ /* On POWER7, we have external interrupts set to use HSRR0/1 */
+11: mtspr SPRN_HSRR0, r8
mtspr SPRN_HSRR1, r7
ba 0x500

@@ -1180,7 +1182,7 @@ kvmppc_hdsi:
cmpdi r3, 0 /* retry the instruction */
beq 6f
cmpdi r3, -1 /* handle in kernel mode */
- beq nohpte_cont
+ beq guest_exit_cont
cmpdi r3, -2 /* MMIO emulation; need instr word */
beq 2f

@@ -1194,6 +1196,7 @@ kvmppc_hdsi:
li r10, BOOK3S_INTERRUPT_DATA_STORAGE
li r11, (MSR_ME << 1) | 1 /* synthesize MSR_SF | MSR_ME */
rotldi r11, r11, 63
+fast_interrupt_c_return:
6: ld r7, VCPU_CTR(r9)
lwz r8, VCPU_XER(r9)
mtctr r7
@@ -1226,7 +1229,7 @@ kvmppc_hdsi:
/* Unset guest mode. */
li r0, KVM_GUEST_MODE_NONE
stb r0, HSTATE_IN_GUEST(r13)
- b nohpte_cont
+ b guest_exit_cont

/*
* Similarly for an HISI, reflect it to the guest as an ISI unless
@@ -1252,9 +1255,9 @@ kvmppc_hisi:
ld r11, VCPU_MSR(r9)
li r12, BOOK3S_INTERRUPT_H_INST_STORAGE
cmpdi r3, 0 /* retry the instruction */
- beq 6f
+ beq fast_interrupt_c_return
cmpdi r3, -1 /* handle in kernel mode */
- beq nohpte_cont
+ beq guest_exit_cont

/* Synthesize an ISI for the guest */
mr r11, r3
@@ -1263,12 +1266,7 @@ kvmppc_hisi:
li r10, BOOK3S_INTERRUPT_INST_STORAGE
li r11, (MSR_ME << 1) | 1 /* synthesize MSR_SF | MSR_ME */
rotldi r11, r11, 63
-6: ld r7, VCPU_CTR(r9)
- lwz r8, VCPU_XER(r9)
- mtctr r7
- mtxer r8
- mr r4, r9
- b fast_guest_return
+ b fast_interrupt_c_return

3: ld r6, VCPU_KVM(r9) /* not relocated, use VRMA */
ld r5, KVM_VRMA_SLB_V(r6)
@@ -1284,14 +1282,14 @@ kvmppc_hisi:
hcall_try_real_mode:
ld r3,VCPU_GPR(R3)(r9)
andi. r0,r11,MSR_PR
- bne hcall_real_cont
+ bne guest_exit_cont
clrrdi r3,r3,2
cmpldi r3,hcall_real_table_end - hcall_real_table
- bge hcall_real_cont
+ bge guest_exit_cont
LOAD_REG_ADDR(r4, hcall_real_table)
lwzx r3,r3,r4
cmpwi r3,0
- beq hcall_real_cont
+ beq guest_exit_cont
add r3,r3,r4
mtctr r3
mr r3,r9 /* get vcpu pointer */
@@ -1312,7 +1310,7 @@ hcall_real_fallback:
li r12,BOOK3S_INTERRUPT_SYSCALL
ld r9, HSTATE_KVM_VCPU(r13)

- b hcall_real_cont
+ b guest_exit_cont

.globl hcall_real_table
hcall_real_table:
@@ -1571,6 +1569,21 @@ kvm_cede_exit:
li r3,H_TOO_HARD
blr

+ /* Try to handle a machine check in real mode */
+machine_check_realmode:
+ mr r3, r9 /* get vcpu pointer */
+ bl .kvmppc_realmode_machine_check
+ nop
+ cmpdi r3, 0 /* continue exiting from guest? */
+ ld r9, HSTATE_KVM_VCPU(r13)
+ li r12, BOOK3S_INTERRUPT_MACHINE_CHECK
+ beq mc_cont
+ /* If not, deliver a machine check. SRR0/1 are already set */
+ li r10, BOOK3S_INTERRUPT_MACHINE_CHECK
+ li r11, (MSR_ME << 1) | 1 /* synthesize MSR_SF | MSR_ME */
+ rotldi r11, r11, 63
+ b fast_interrupt_c_return
+
secondary_too_late:
ld r5,HSTATE_KVM_VCORE(r13)
HMT_LOW
--
1.7.10.rc3.219.g53414