KVM: PPC: Book3S HV: Complete passthrough interrupt in host

In existing real mode ICP code, when updating the virtual ICP
state, if there is a required action that cannot be completely
handled in real mode, as for instance, a VCPU needs to be woken
up, flags are set in the ICP to indicate the required action.
This is checked when returning from hypercalls to decide whether
the call needs switch back to the host where the action can be
performed in virtual mode. Note that if h_ipi_redirect is enabled,
real mode code will first try to message a free host CPU to
complete this job instead of returning the host to do it ourselves.

Currently, the real mode PCI passthrough interrupt handling code
checks if any of these flags are set and simply returns to the host.
This is not good enough as the trap value (0x500) is treated as an
external interrupt by the host code. It is only when the trap value
is a hypercall that the host code searches for and acts on unfinished
work by calling kvmppc_xics_rm_complete.

This patch introduces a special trap BOOK3S_INTERRUPT_HV_RM_HARD
which is returned by KVM if there is unfinished business to be
completed in host virtual mode after handling a PCI passthrough
interrupt. The host checks for this special interrupt condition
and calls into the kvmppc_xics_rm_complete, which is made an
exported function for this reason.

[paulus@ozlabs.org - moved logic to set r12 to BOOK3S_INTERRUPT_HV_RM_HARD
 in book3s_hv_rmhandlers.S into the end of kvmppc_check_wake_reason.]

Signed-off-by: Suresh Warrier <warrier@linux.vnet.ibm.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

1 files changed, 25 insertions, 0 deletions

diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index 12fb2afb23fc..7cc924b5eea2 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -1189,6 +1189,11 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 	 *   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.
@@ -1204,6 +1209,15 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 	 *    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
 
@@ -2419,6 +2433,17 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
 	bl	kvmppc_read_intr
 	nop
 	li	r12, BOOK3S_INTERRUPT_EXTERNAL
+	cmpdi	r3, 1
+	ble	1f
+
+	/*
+	 * Return code of 2 means PCI passthrough interrupt, but
+	 * we need to return back to host to complete handling the
+	 * interrupt. Trap reason is expected in r12 by guest
+	 * exit code.
+	 */
+	li	r12, BOOK3S_INTERRUPT_HV_RM_HARD
+1:
 	ld	r0, PPC_MIN_STKFRM+PPC_LR_STKOFF(r1)
 	addi	r1, r1, PPC_MIN_STKFRM
 	mtlr	r0