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KVM: PPC: Book3S HV: Simplify real-mode interrupt handling
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This streamlines the first part of the code that handles a hypervisor
interrupt that occurred in the guest.  With this, all of the real-mode
handling that occurs is done before the "guest_exit_cont" label; once
we get to that label we are committed to exiting to host virtual mode.
Thus the machine check and HMI real-mode handling is moved before that
label.

Also, the code to handle external interrupts is moved out of line, as
is the code that calls kvmppc_realmode_hmi_handler().

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
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Paul Mackerras authored and Michael Ellerman committed Oct 9, 2018
1 parent 41f4e63 commit df709a2
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Showing 2 changed files with 119 additions and 109 deletions.
8 changes: 8 additions & 0 deletions arch/powerpc/kvm/book3s_hv_ras.c
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Original file line number Diff line number Diff line change
Expand Up @@ -331,5 +331,13 @@ long kvmppc_realmode_hmi_handler(void)
} else {
wait_for_tb_resync();
}

/*
* Reset tb_offset_applied so the guest exit code won't try
* to subtract the previous timebase offset from the timebase.
*/
if (local_paca->kvm_hstate.kvm_vcore)
local_paca->kvm_hstate.kvm_vcore->tb_offset_applied = 0;

return 0;
}
220 changes: 111 additions & 109 deletions arch/powerpc/kvm/book3s_hv_rmhandlers.S
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Original file line number Diff line number Diff line change
Expand Up @@ -1018,8 +1018,7 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_ARCH_300)
no_xive:
#endif /* CONFIG_KVM_XICS */

deliver_guest_interrupt:
kvmppc_cede_reentry: /* r4 = vcpu, r13 = paca */
deliver_guest_interrupt: /* r4 = vcpu, r13 = paca */
/* Check if we can deliver an external or decrementer interrupt now */
ld r0, VCPU_PENDING_EXC(r4)
BEGIN_FTR_SECTION
Expand Down Expand Up @@ -1269,18 +1268,26 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
std r3, VCPU_CTR(r9)
std r4, VCPU_XER(r9)

#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
/* For softpatch interrupt, go off and do TM instruction emulation */
cmpwi r12, BOOK3S_INTERRUPT_HV_SOFTPATCH
beq kvmppc_tm_emul
#endif
/* Save more register state */
mfdar r3
mfdsisr r4
std r3, VCPU_DAR(r9)
stw r4, VCPU_DSISR(r9)

/* If this is a page table miss then see if it's theirs or ours */
cmpwi r12, BOOK3S_INTERRUPT_H_DATA_STORAGE
beq kvmppc_hdsi
std r3, VCPU_FAULT_DAR(r9)
stw r4, VCPU_FAULT_DSISR(r9)
cmpwi r12, BOOK3S_INTERRUPT_H_INST_STORAGE
beq kvmppc_hisi

#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
/* For softpatch interrupt, go off and do TM instruction emulation */
cmpwi r12, BOOK3S_INTERRUPT_HV_SOFTPATCH
beq kvmppc_tm_emul
#endif

/* See if this is a leftover HDEC interrupt */
cmpwi r12,BOOK3S_INTERRUPT_HV_DECREMENTER
bne 2f
Expand All @@ -1303,7 +1310,7 @@ BEGIN_FTR_SECTION
END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
lbz r0, HSTATE_HOST_IPI(r13)
cmpwi r0, 0
beq 4f
beq maybe_reenter_guest
b guest_exit_cont
3:
/* If it's a hypervisor facility unavailable interrupt, save HFSCR */
Expand All @@ -1315,82 +1322,16 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
14:
/* External interrupt ? */
cmpwi r12, BOOK3S_INTERRUPT_EXTERNAL
bne+ guest_exit_cont

/* External interrupt, first check for host_ipi. If this is
* set, we know the host wants us out so let's do it now
*/
bl kvmppc_read_intr

/*
* Restore the active volatile registers after returning from
* a C function.
*/
ld r9, HSTATE_KVM_VCPU(r13)
li r12, BOOK3S_INTERRUPT_EXTERNAL

/*
* kvmppc_read_intr return codes:
*
* Exit to host (r3 > 0)
* 1 An interrupt is pending that needs to be handled by the host
* Exit guest and return to host by branching to guest_exit_cont
*
* 2 Passthrough that needs completion in the host
* Exit guest and return to host by branching to guest_exit_cont
* However, we also set r12 to BOOK3S_INTERRUPT_HV_RM_HARD
* to indicate to the host to complete handling the interrupt
*
* Before returning to guest, we check if any CPU is heading out
* to the host and if so, we head out also. If no CPUs are heading
* check return values <= 0.
*
* Return to guest (r3 <= 0)
* 0 No external interrupt is pending
* -1 A guest wakeup IPI (which has now been cleared)
* In either case, we return to guest to deliver any pending
* guest interrupts.
*
* -2 A PCI passthrough external interrupt was handled
* (interrupt was delivered directly to guest)
* Return to guest to deliver any pending guest interrupts.
*/

cmpdi r3, 1
ble 1f

/* Return code = 2 */
li r12, BOOK3S_INTERRUPT_HV_RM_HARD
stw r12, VCPU_TRAP(r9)
b guest_exit_cont

1: /* Return code <= 1 */
cmpdi r3, 0
bgt guest_exit_cont

/* Return code <= 0 */
4: ld r5, HSTATE_KVM_VCORE(r13)
lwz r0, VCORE_ENTRY_EXIT(r5)
cmpwi r0, 0x100
mr r4, r9
blt deliver_guest_interrupt

guest_exit_cont: /* r9 = vcpu, r12 = trap, r13 = paca */
/* Save more register state */
mfdar r6
mfdsisr r7
std r6, VCPU_DAR(r9)
stw r7, VCPU_DSISR(r9)
/* don't overwrite fault_dar/fault_dsisr if HDSI */
cmpwi r12,BOOK3S_INTERRUPT_H_DATA_STORAGE
beq mc_cont
std r6, VCPU_FAULT_DAR(r9)
stw r7, VCPU_FAULT_DSISR(r9)

beq kvmppc_guest_external
/* See if it is a machine check */
cmpwi r12, BOOK3S_INTERRUPT_MACHINE_CHECK
beq machine_check_realmode
mc_cont:
/* Or a hypervisor maintenance interrupt */
cmpwi r12, BOOK3S_INTERRUPT_HMI
beq hmi_realmode

guest_exit_cont: /* r9 = vcpu, r12 = trap, r13 = paca */

#ifdef CONFIG_KVM_BOOK3S_HV_EXIT_TIMING
addi r3, r9, VCPU_TB_RMEXIT
mr r4, r9
Expand Down Expand Up @@ -1821,24 +1762,6 @@ BEGIN_FTR_SECTION
mtspr SPRN_DPDES, r8
END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)

/* If HMI, call kvmppc_realmode_hmi_handler() */
lwz r12, STACK_SLOT_TRAP(r1)
cmpwi r12, BOOK3S_INTERRUPT_HMI
bne 27f
bl kvmppc_realmode_hmi_handler
nop
cmpdi r3, 0
/*
* 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().
*/
beq 30f

27:
/* Subtract timebase offset from timebase */
ld r8, VCORE_TB_OFFSET_APPL(r5)
cmpdi r8,0
Expand All @@ -1856,7 +1779,16 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
addis r8,r8,0x100 /* if so, increment upper 40 bits */
mtspr SPRN_TBU40,r8

17: bl kvmppc_subcore_exit_guest
17:
/*
* If this is an HMI, we called kvmppc_realmode_hmi_handler
* above, which may or may not have already called
* kvmppc_subcore_exit_guest. Fortunately, all that
* kvmppc_subcore_exit_guest does is clear a flag, so calling
* it again here is benign even if kvmppc_realmode_hmi_handler
* has already called it.
*/
bl kvmppc_subcore_exit_guest
nop
30: ld r5,HSTATE_KVM_VCORE(r13)
ld r4,VCORE_KVM(r5) /* pointer to struct kvm */
Expand Down Expand Up @@ -1910,6 +1842,67 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
mtlr r0
blr

kvmppc_guest_external:
/* External interrupt, first check for host_ipi. If this is
* set, we know the host wants us out so let's do it now
*/
bl kvmppc_read_intr

/*
* Restore the active volatile registers after returning from
* a C function.
*/
ld r9, HSTATE_KVM_VCPU(r13)
li r12, BOOK3S_INTERRUPT_EXTERNAL

/*
* kvmppc_read_intr return codes:
*
* Exit to host (r3 > 0)
* 1 An interrupt is pending that needs to be handled by the host
* Exit guest and return to host by branching to guest_exit_cont
*
* 2 Passthrough that needs completion in the host
* Exit guest and return to host by branching to guest_exit_cont
* However, we also set r12 to BOOK3S_INTERRUPT_HV_RM_HARD
* to indicate to the host to complete handling the interrupt
*
* Before returning to guest, we check if any CPU is heading out
* to the host and if so, we head out also. If no CPUs are heading
* check return values <= 0.
*
* Return to guest (r3 <= 0)
* 0 No external interrupt is pending
* -1 A guest wakeup IPI (which has now been cleared)
* In either case, we return to guest to deliver any pending
* guest interrupts.
*
* -2 A PCI passthrough external interrupt was handled
* (interrupt was delivered directly to guest)
* Return to guest to deliver any pending guest interrupts.
*/

cmpdi r3, 1
ble 1f

/* Return code = 2 */
li r12, BOOK3S_INTERRUPT_HV_RM_HARD
stw r12, VCPU_TRAP(r9)
b guest_exit_cont

1: /* Return code <= 1 */
cmpdi r3, 0
bgt guest_exit_cont

/* Return code <= 0 */
maybe_reenter_guest:
ld r5, HSTATE_KVM_VCORE(r13)
lwz r0, VCORE_ENTRY_EXIT(r5)
cmpwi r0, 0x100
mr r4, r9
blt deliver_guest_interrupt
b guest_exit_cont

#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
/*
* Softpatch interrupt for transactional memory emulation cases
Expand Down Expand Up @@ -2685,13 +2678,7 @@ END_FTR_SECTION(CPU_FTR_TM | CPU_FTR_P9_TM_HV_ASSIST, 0)
mr r9, r4
cmpdi r3, 0
bgt guest_exit_cont

/* see if any other thread is already exiting */
lwz r0,VCORE_ENTRY_EXIT(r5)
cmpwi r0,0x100
bge guest_exit_cont

b kvmppc_cede_reentry /* if not go back to guest */
b maybe_reenter_guest

/* cede when already previously prodded case */
kvm_cede_prodded:
Expand Down Expand Up @@ -2758,12 +2745,12 @@ machine_check_realmode:
*/
ld r11, VCPU_MSR(r9)
rldicl. r0, r11, 64-MSR_HV_LG, 63 /* check if it happened in HV mode */
bne mc_cont /* if so, exit to host */
bne guest_exit_cont /* if so, exit to host */
/* Check if guest is capable of handling NMI exit */
ld r10, VCPU_KVM(r9)
lbz r10, KVM_FWNMI(r10)
cmpdi r10, 1 /* FWNMI capable? */
beq mc_cont /* if so, exit with KVM_EXIT_NMI. */
beq guest_exit_cont /* if so, exit with KVM_EXIT_NMI. */

/* if not, fall through for backward compatibility. */
andi. r10, r11, MSR_RI /* check for unrecoverable exception */
Expand All @@ -2776,6 +2763,21 @@ machine_check_realmode:
bl kvmppc_msr_interrupt
2: b fast_interrupt_c_return

/*
* Call C code to handle a HMI in real mode.
* Only the primary thread does the call, secondary threads are handled
* by calling hmi_exception_realmode() after kvmppc_hv_entry returns.
* r9 points to the vcpu on entry
*/
hmi_realmode:
lbz r0, HSTATE_PTID(r13)
cmpwi r0, 0
bne guest_exit_cont
bl kvmppc_realmode_hmi_handler
ld r9, HSTATE_KVM_VCPU(r13)
li r12, BOOK3S_INTERRUPT_HMI
b guest_exit_cont

/*
* Check the reason we woke from nap, and take appropriate action.
* Returns (in r3):
Expand Down

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