KVM: PPC: Book3S HV: Convert kvmppc_read_intr to a C function
Modify kvmppc_read_intr to make it a C function. Because it is called
from kvmppc_check_wake_reason, any of the assembler code that calls
either kvmppc_read_intr or kvmppc_check_wake_reason now has to assume
that the volatile registers might have been modified.
This also adds in the optimization of clearing saved_xirr in the case
where we completely handle and EOI an IPI. Without this, the next
device interrupt will require two trips through the host interrupt
handling code.
[paulus@ozlabs.org - made kvmppc_check_wake_reason create a stack frame
when it is calling kvmppc_read_intr, which means we can set r12 to
the trap number (0x500) after the call to kvmppc_read_intr, instead
of using r31. Also moved the deliver_guest_interrupt label so as to
restore XER and CTR, plus other minor tweaks.]
Signed-off-by: Suresh Warrier <warrier@linux.vnet.ibm.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index 9756555..dccfa85 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -221,6 +221,13 @@
li r3, 0 /* Don't wake on privileged (OS) doorbell */
b kvm_do_nap
+/*
+ * kvm_novcpu_wakeup
+ * Entered from kvm_start_guest if kvm_hstate.napping is set
+ * to NAPPING_NOVCPU
+ * r2 = kernel TOC
+ * r13 = paca
+ */
kvm_novcpu_wakeup:
ld r1, HSTATE_HOST_R1(r13)
ld r5, HSTATE_KVM_VCORE(r13)
@@ -230,6 +237,13 @@
/* check the wake reason */
bl kvmppc_check_wake_reason
+ /*
+ * Restore volatile registers since we could have called
+ * a C routine in kvmppc_check_wake_reason.
+ * r5 = VCORE
+ */
+ ld r5, HSTATE_KVM_VCORE(r13)
+
/* see if any other thread is already exiting */
lwz r0, VCORE_ENTRY_EXIT(r5)
cmpwi r0, 0x100
@@ -322,6 +336,11 @@
/* Check the wake reason in SRR1 to see why we got here */
bl kvmppc_check_wake_reason
+ /*
+ * kvmppc_check_wake_reason could invoke a C routine, but we
+ * have no volatile registers to restore when we return.
+ */
+
cmpdi r3, 0
bge kvm_no_guest
@@ -881,6 +900,7 @@
cmpwi r3, 512 /* 1 microsecond */
blt hdec_soon
+deliver_guest_interrupt:
ld r6, VCPU_CTR(r4)
ld r7, VCPU_XER(r4)
@@ -895,7 +915,6 @@
mtspr SPRN_SRR0, r6
mtspr SPRN_SRR1, r7
-deliver_guest_interrupt:
/* r11 = vcpu->arch.msr & ~MSR_HV */
rldicl r11, r11, 63 - MSR_HV_LG, 1
rotldi r11, r11, 1 + MSR_HV_LG
@@ -1155,10 +1174,36 @@
* 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
+ *
+ * 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.
+ */
+
cmpdi r3, 0
bgt guest_exit_cont
- /* Check if any CPU is heading out to the host, if so head out too */
+ /* Return code <= 0 */
4: ld r5, HSTATE_KVM_VCORE(r13)
lwz r0, VCORE_ENTRY_EXIT(r5)
cmpwi r0, 0x100
@@ -2213,10 +2258,20 @@
ld r29, VCPU_GPR(R29)(r4)
ld r30, VCPU_GPR(R30)(r4)
ld r31, VCPU_GPR(R31)(r4)
-
+
/* Check the wake reason in SRR1 to see why we got here */
bl kvmppc_check_wake_reason
+ /*
+ * Restore volatile registers since we could have called a
+ * C routine in kvmppc_check_wake_reason
+ * r4 = VCPU
+ * r3 tells us whether we need to return to host or not
+ * WARNING: it gets checked further down:
+ * should not modify r3 until this check is done.
+ */
+ ld r4, HSTATE_KVM_VCPU(r13)
+
/* clear our bit in vcore->napping_threads */
34: ld r5,HSTATE_KVM_VCORE(r13)
lbz r7,HSTATE_PTID(r13)
@@ -2230,7 +2285,7 @@
li r0,0
stb r0,HSTATE_NAPPING(r13)
- /* See if the wake reason means we need to exit */
+ /* See if the wake reason saved in r3 means we need to exit */
stw r12, VCPU_TRAP(r4)
mr r9, r4
cmpdi r3, 0
@@ -2300,7 +2355,9 @@
*
* Also sets r12 to the interrupt vector for any interrupt that needs
* to be handled now by the host (0x500 for external interrupt), or zero.
- * Modifies r0, r6, r7, r8.
+ * Modifies all volatile registers (since it may call a C function).
+ * This routine calls kvmppc_read_intr, a C function, if an external
+ * interrupt is pending.
*/
kvmppc_check_wake_reason:
mfspr r6, SPRN_SRR1
@@ -2310,8 +2367,7 @@
rlwinm r6, r6, 45-31, 0xe /* P7 wake reason field is 3 bits */
ALT_FTR_SECTION_END_IFSET(CPU_FTR_ARCH_207S)
cmpwi r6, 8 /* was it an external interrupt? */
- li r12, BOOK3S_INTERRUPT_EXTERNAL
- beq kvmppc_read_intr /* if so, see what it was */
+ beq 7f /* if so, see what it was */
li r3, 0
li r12, 0
cmpwi r6, 6 /* was it the decrementer? */
@@ -2350,83 +2406,17 @@
li r3, 1
blr
-/*
- * Determine what sort of external interrupt is pending (if any).
- * Returns:
- * 0 if no interrupt is pending
- * 1 if an interrupt is pending that needs to be handled by the host
- * -1 if there was a guest wakeup IPI (which has now been cleared)
- * Modifies r0, r6, r7, r8, returns value in r3.
- */
-kvmppc_read_intr:
- /* see if a host IPI is pending */
- li r3, 1
- lbz r0, HSTATE_HOST_IPI(r13)
- cmpwi r0, 0
- bne 1f
-
- /* Now read the interrupt from the ICP */
- ld r6, HSTATE_XICS_PHYS(r13)
- li r7, XICS_XIRR
- cmpdi r6, 0
- beq- 1f
- lwzcix r0, r6, r7
- /*
- * Save XIRR for later. Since we get in in reverse endian on LE
- * systems, save it byte reversed and fetch it back in host endian.
- */
- li r3, HSTATE_SAVED_XIRR
- STWX_BE r0, r3, r13
-#ifdef __LITTLE_ENDIAN__
- lwz r3, HSTATE_SAVED_XIRR(r13)
-#else
- mr r3, r0
-#endif
- rlwinm. r3, r3, 0, 0xffffff
- sync
- beq 1f /* if nothing pending in the ICP */
-
- /* We found something in the ICP...
- *
- * If it's not an IPI, stash it in the PACA and return to
- * the host, we don't (yet) handle directing real external
- * interrupts directly to the guest
- */
- cmpwi r3, XICS_IPI /* if there is, is it an IPI? */
- bne 42f
-
- /* It's an IPI, clear the MFRR and EOI it */
- li r3, 0xff
- li r8, XICS_MFRR
- stbcix r3, r6, r8 /* clear the IPI */
- stwcix r0, r6, r7 /* EOI it */
- sync
-
- /* We need to re-check host IPI now in case it got set in the
- * meantime. If it's clear, we bounce the interrupt to the
- * guest
- */
- lbz r0, HSTATE_HOST_IPI(r13)
- cmpwi r0, 0
- bne- 43f
-
- /* OK, it's an IPI for us */
- li r12, 0
- li r3, -1
-1: blr
-
-42: /* It's not an IPI and it's for the host. We saved a copy of XIRR in
- * the PACA earlier, it will be picked up by the host ICP driver
- */
- li r3, 1
- b 1b
-
-43: /* We raced with the host, we need to resend that IPI, bummer */
- li r0, IPI_PRIORITY
- stbcix r0, r6, r8 /* set the IPI */
- sync
- li r3, 1
- b 1b
+ /* external interrupt - create a stack frame so we can call C */
+7: mflr r0
+ std r0, PPC_LR_STKOFF(r1)
+ stdu r1, -PPC_MIN_STKFRM(r1)
+ bl kvmppc_read_intr
+ nop
+ li r12, BOOK3S_INTERRUPT_EXTERNAL
+ ld r0, PPC_MIN_STKFRM+PPC_LR_STKOFF(r1)
+ addi r1, r1, PPC_MIN_STKFRM
+ mtlr r0
+ blr
/*
* Save away FP, VMX and VSX registers.
