forked from Minki/linux
powerpc: Provide a way for KVM to indicate that NV GPR values are lost
This fixes a problem where a CPU thread coming out of nap mode can think it has valid values in the nonvolatile GPRs (r14 - r31) as saved away in power7_idle, but in fact the values have been trashed because the thread was used for KVM in the mean time. The result is that the thread crashes because code that called power7_idle (e.g., pnv_smp_cpu_kill_self()) goes to use values in registers that have been trashed. The bit field in SRR1 that tells whether state was lost only reflects the most recent nap, which may not have been the nap instruction in power7_idle. So we need an extra PACA field to indicate that state has been lost even if SRR1 indicates that the most recent nap didn't lose state. We clear this field when saving the state in power7_idle, we set it to a non-zero value when we use the thread for KVM, and we test it in power7_wakeup_noloss. Signed-off-by: Paul Mackerras <paulus@samba.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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@ -135,6 +135,7 @@ struct paca_struct {
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u8 hard_enabled; /* set if irqs are enabled in MSR */
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u8 io_sync; /* writel() needs spin_unlock sync */
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u8 irq_work_pending; /* IRQ_WORK interrupt while soft-disable */
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u8 nap_state_lost; /* NV GPR values lost in power7_idle */
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#ifdef CONFIG_PPC_POWERNV
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/* Pointer to OPAL machine check event structure set by the
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@ -208,6 +208,7 @@ int main(void)
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DEFINE(PACA_USER_TIME, offsetof(struct paca_struct, user_time));
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DEFINE(PACA_SYSTEM_TIME, offsetof(struct paca_struct, system_time));
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DEFINE(PACA_TRAP_SAVE, offsetof(struct paca_struct, trap_save));
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DEFINE(PACA_NAPSTATELOST, offsetof(struct paca_struct, nap_state_lost));
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#endif /* CONFIG_PPC64 */
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/* RTAS */
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@ -54,6 +54,7 @@ _GLOBAL(power7_idle)
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li r0,0
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stb r0,PACASOFTIRQEN(r13) /* we'll hard-enable shortly */
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stb r0,PACAHARDIRQEN(r13)
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stb r0,PACA_NAPSTATELOST(r13)
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/* Continue saving state */
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SAVE_GPR(2, r1)
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@ -86,6 +87,9 @@ _GLOBAL(power7_wakeup_loss)
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rfid
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_GLOBAL(power7_wakeup_noloss)
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lbz r0,PACA_NAPSTATELOST(r13)
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cmpwi r0,0
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bne .power7_wakeup_loss
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ld r1,PACAR1(r13)
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ld r4,_MSR(r1)
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ld r5,_NIP(r1)
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@ -112,6 +112,9 @@ kvm_start_guest:
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stbcix r0, r5, r6 /* clear it */
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stwcix r8, r5, r7 /* EOI it */
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/* NV GPR values from power7_idle() will no longer be valid */
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stb r0, PACA_NAPSTATELOST(r13)
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.global kvmppc_hv_entry
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kvmppc_hv_entry:
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