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KVM: PPC: Book3S HV: Synthesize segment fault if SLB lookup fails

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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 <thuth@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>
This commit is contained in:
Paul Mackerras 2015-10-27 16:10:20 +11:00
parent a3eaa8649e
commit cf29b21595
1 changed files with 12 additions and 8 deletions
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20
arch/powerpc/kvm/book3s_hv_rmhandlers.S
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@ -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