From cf29b21595b91eecce6ca69b0f92d60bca076ef0 Mon Sep 17 00:00:00 2001 From: Paul Mackerras Date: Tue, 27 Oct 2015 16:10:20 +1100 Subject: KVM: PPC: Book3S HV: Synthesize segment fault if SLB lookup fails When handling a hypervisor data or instruction storage interrupt (HDSI or HISI), we look up the SLB entry for the address being accessed in order to translate the effective address to a virtual address which can be looked up in the guest HPT. This lookup can occasionally fail due to the guest replacing an SLB entry without invalidating the evicted SLB entry. In this situation an ERAT (effective to real address translation cache) entry can persist and be used by the hardware even though there is no longer a corresponding SLB entry. Previously we would just deliver a data or instruction storage interrupt (DSI or ISI) to the guest in this case. However, this is not correct and has been observed to cause guests to crash, typically with a data storage protection interrupt on a store to the vmemmap area. Instead, what we do now is to synthesize a data or instruction segment interrupt. That should cause the guest to reload an appropriate entry into the SLB and retry the faulting instruction. If it still faults, we should find an appropriate SLB entry next time and be able to handle the fault. Tested-by: Thomas Huth Reviewed-by: David Gibson Signed-off-by: Paul Mackerras diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S index b1dab8d..3c6badc 100644 --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S @@ -1749,7 +1749,8 @@ kvmppc_hdsi: beq 3f clrrdi r0, r4, 28 PPC_SLBFEE_DOT(R5, R0) /* if so, look up SLB */ - bne 1f /* if no SLB entry found */ + li r0, BOOK3S_INTERRUPT_DATA_SEGMENT + bne 7f /* if no SLB entry found */ 4: std r4, VCPU_FAULT_DAR(r9) stw r6, VCPU_FAULT_DSISR(r9) @@ -1768,14 +1769,15 @@ kvmppc_hdsi: cmpdi r3, -2 /* MMIO emulation; need instr word */ beq 2f - /* Synthesize a DSI for the guest */ + /* Synthesize a DSI (or DSegI) for the guest */ ld r4, VCPU_FAULT_DAR(r9) mr r6, r3 -1: mtspr SPRN_DAR, r4 +1: li r0, BOOK3S_INTERRUPT_DATA_STORAGE mtspr SPRN_DSISR, r6 +7: mtspr SPRN_DAR, r4 mtspr SPRN_SRR0, r10 mtspr SPRN_SRR1, r11 - li r10, BOOK3S_INTERRUPT_DATA_STORAGE + mr r10, r0 bl kvmppc_msr_interrupt fast_interrupt_c_return: 6: ld r7, VCPU_CTR(r9) @@ -1823,7 +1825,8 @@ kvmppc_hisi: beq 3f clrrdi r0, r10, 28 PPC_SLBFEE_DOT(R5, R0) /* if so, look up SLB */ - bne 1f /* if no SLB entry found */ + li r0, BOOK3S_INTERRUPT_INST_SEGMENT + bne 7f /* if no SLB entry found */ 4: /* Search the hash table. */ mr r3, r9 /* vcpu pointer */ @@ -1840,11 +1843,12 @@ kvmppc_hisi: cmpdi r3, -1 /* handle in kernel mode */ beq guest_exit_cont - /* Synthesize an ISI for the guest */ + /* Synthesize an ISI (or ISegI) for the guest */ mr r11, r3 -1: mtspr SPRN_SRR0, r10 +1: li r0, BOOK3S_INTERRUPT_INST_STORAGE +7: mtspr SPRN_SRR0, r10 mtspr SPRN_SRR1, r11 - li r10, BOOK3S_INTERRUPT_INST_STORAGE + mr r10, r0 bl kvmppc_msr_interrupt b fast_interrupt_c_return -- cgit v0.10.2 From f74f2e2e26199f695ca3df94f29e9ab7cb707ea4 Mon Sep 17 00:00:00 2001 From: Paul Mackerras Date: Tue, 3 Nov 2015 16:03:30 +1100 Subject: KVM: PPC: Book3S HV: Don't dynamically split core when already split In static micro-threading modes, the dynamic micro-threading code is supposed to be disabled, because subcores can't make independent decisions about what micro-threading mode to put the core in - there is only one micro-threading mode for the whole core. The code that implements dynamic micro-threading checks for this, except that the check was missed in one case. This means that it is possible for a subcore in static 2-way micro-threading mode to try to put the core into 4-way micro-threading mode, which usually leads to stuck CPUs, spinlock lockups, and other stalls in the host. The problem was in the can_split_piggybacked_subcores() function, which should always return false if the system is in a static micro-threading mode. This fixes the problem by making can_split_piggybacked_subcores() use subcore_config_ok() for its checks, as subcore_config_ok() includes the necessary check for the static micro-threading modes. Credit to Gautham Shenoy for working out that the reason for the hangs and stalls we were seeing was that we were trying to do dynamic 4-way micro-threading while we were in static 2-way mode. Fixes: b4deba5c41e9 Cc: vger@stable.kernel.org # v4.3 Signed-off-by: Paul Mackerras diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c index 2280497..becad3a 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -2060,7 +2060,7 @@ static bool can_split_piggybacked_subcores(struct core_info *cip) return false; n_subcores += (cip->subcore_threads[sub] - 1) >> 1; } - if (n_subcores > 3 || large_sub < 0) + if (large_sub < 0 || !subcore_config_ok(n_subcores + 1, 2)) return false; /* -- cgit v0.10.2