[PATCH v4 6/6] powerpc/kvm/xive: Keep escalation interrupt masked unless ceded
Benjamin Herrenschmidt
benh at kernel.crashing.org
Fri Jan 12 13:37:16 AEDT 2018
This works on top of the single escalation support. When in single
escalation, with this change, we will keep the escalation interrupt
disabled unless the VCPU is in H_CEDE (idle). In any other case, we
know the VCPU will be rescheduled and thus there is no need to take
escalation interrupts in the host whenever a guest interrupt fires.
Signed-off-by: Benjamin Herrenschmidt <benh at kernel.crashing.org>
---
arch/powerpc/include/asm/kvm_host.h | 3 ++
arch/powerpc/kernel/asm-offsets.c | 3 ++
arch/powerpc/kvm/book3s_hv_rmhandlers.S | 62 ++++++++++++++++++++++++++++++++-
arch/powerpc/kvm/book3s_xive.c | 30 ++++++++++++++++
4 files changed, 97 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index 0c44fa67608d..fef8133becc8 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -740,7 +740,10 @@ struct kvm_vcpu_arch {
struct kvmppc_xive_vcpu *xive_vcpu; /* XIVE virtual CPU data */
__be32 xive_cam_word; /* Cooked W2 in proper endian with valid bit */
u8 xive_pushed; /* Is the VP pushed on the physical CPU ? */
+ u8 xive_esc_on; /* Is the escalation irq enabled ? */
union xive_tma_w01 xive_saved_state; /* W0..1 of XIVE thread state */
+ u64 xive_esc_raddr; /* Escalation interrupt ESB real addr */
+ u64 xive_esc_vaddr; /* Escalation interrupt ESB virt addr */
#endif
#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index 825089cf3e23..1672dffd94e2 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -734,6 +734,9 @@ int main(void)
DEFINE(VCPU_XIVE_CAM_WORD, offsetof(struct kvm_vcpu,
arch.xive_cam_word));
DEFINE(VCPU_XIVE_PUSHED, offsetof(struct kvm_vcpu, arch.xive_pushed));
+ DEFINE(VCPU_XIVE_ESC_ON, offsetof(struct kvm_vcpu, arch.xive_esc_on));
+ DEFINE(VCPU_XIVE_ESC_RADDR, offsetof(struct kvm_vcpu, arch.xive_esc_raddr));
+ DEFINE(VCPU_XIVE_ESC_VADDR, offsetof(struct kvm_vcpu, arch.xive_esc_vaddr));
#endif
#ifdef CONFIG_KVM_EXIT_TIMING
diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index 46dc250d072a..b76878a648ef 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -1043,6 +1043,41 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_ARCH_300)
*/
li r0,0
stb r0, VCPU_IRQ_PENDING(r4)
+
+ /*
+ * In single escalation mode, if the escalation interrupt is
+ * on, we mask it.
+ */
+ lbz r0, VCPU_XIVE_ESC_ON(r4)
+ cmpwi r0,0
+ beq 1f
+ ld r10, VCPU_XIVE_ESC_RADDR(r4)
+ li r9, XIVE_ESB_SET_PQ_01
+ ldcix r0, r10, r9
+ sync
+
+ /* We have a possible subtle race here: The escalation interrupt might
+ * have fired and be on its way to the host queue while we mask it,
+ * and if we unmask it early enough (re-cede right away), there is
+ * a theorical possibility that it fires again, thus landing in the
+ * target queue more than once which is a big no-no.
+ *
+ * Fortunately, solving this is rather easy. If the above load setting
+ * PQ to 01 returns a previous value where P is set, then we know the
+ * escalation interrupt is somewhere on its way to the host. In that
+ * case we simply don't clear the xive_esc_on flag below. It will be
+ * eventually cleared by the handler for the escalation interrupt.
+ *
+ * Then, when doing a cede, we check that flag again before re-enabling
+ * the escalation interrupt, and if set, we abort the cede.
+ */
+ andi. r0, r0, XIVE_ESB_VAL_P
+ bne- 1f
+
+ /* Now P is 0, we can clear the flag */
+ li r0, 0
+ stb r0, VCPU_XIVE_ESC_ON(r4)
+1:
no_xive:
#endif /* CONFIG_KVM_XICS */
@@ -2755,7 +2790,32 @@ kvm_cede_prodded:
/* we've ceded but we want to give control to the host */
kvm_cede_exit:
ld r9, HSTATE_KVM_VCPU(r13)
- b guest_exit_cont
+#ifdef CONFIG_KVM_XICS
+ /* Abort if we still have a pending escalation */
+ lbz r5, VCPU_XIVE_ESC_ON(r9)
+ cmpwi r5, 0
+ beq 1f
+ li r0, 0
+ stb r0, VCPU_CEDED(r9)
+1: /* Enable XIVE escalation */
+ li r5, XIVE_ESB_SET_PQ_00
+ mfmsr r0
+ andi. r0, r0, MSR_DR /* in real mode? */
+ beq 1f
+ ld r10, VCPU_XIVE_ESC_VADDR(r9)
+ cmpdi r10, 0
+ beq 3f
+ ldx r0, r10, r5
+ b 2f
+1: ld r10, VCPU_XIVE_ESC_RADDR(r9)
+ cmpdi r10, 0
+ beq 3f
+ ldcix r0, r10, r5
+2: sync
+ li r0, 1
+ stb r0, VCPU_XIVE_ESC_ON(r9)
+#endif /* CONFIG_KVM_XICS */
+3: b guest_exit_cont
/* Try to handle a machine check in real mode */
machine_check_realmode:
diff --git a/arch/powerpc/kvm/book3s_xive.c b/arch/powerpc/kvm/book3s_xive.c
index de78ac38f7ed..badfdbb857a2 100644
--- a/arch/powerpc/kvm/book3s_xive.c
+++ b/arch/powerpc/kvm/book3s_xive.c
@@ -89,6 +89,17 @@ static irqreturn_t xive_esc_irq(int irq, void *data)
if (vcpu->arch.ceded)
kvmppc_fast_vcpu_kick(vcpu);
+ /* Since we have the no-EOI flag, the interrupt is effectively
+ * disabled now. Clearing xive_esc_on means we won't bother
+ * doing so on the next entry.
+ *
+ * This also allows the entry code to know that if a PQ combination
+ * of 10 is observed while xive_esc_on is true, it means the queue
+ * contains an unprocessed escalation interrupt. We don't make use of
+ * that knowledge today but might (see comment in book3s_hv_rmhandler.S)
+ */
+ vcpu->arch.xive_esc_on = false;
+
return IRQ_HANDLED;
}
@@ -134,6 +145,25 @@ static int xive_attach_escalation(struct kvm_vcpu *vcpu, u8 prio)
goto error;
}
xc->esc_virq_names[prio] = name;
+
+ /* In single escalation mode, we grab the ESB MMIO of the
+ * interrupt and mask it. Also populate the VCPU v/raddr
+ * of the ESB page for use by asm entry/exit code. Finally
+ * set the XIVE_IRQ_NO_EOI flag which will prevent the
+ * core code from performing an EOI on the escalation
+ * interrupt, thus leaving it effectively masked after
+ * it fires once.
+ */
+ if (xc->xive->single_escalation) {
+ struct irq_data *d = irq_get_irq_data(xc->esc_virq[prio]);
+ struct xive_irq_data *xd = irq_data_get_irq_handler_data(d);
+
+ xive_vm_esb_load(xd, XIVE_ESB_SET_PQ_01);
+ vcpu->arch.xive_esc_raddr = xd->eoi_page;
+ vcpu->arch.xive_esc_vaddr = (__force u64)xd->eoi_mmio;
+ xd->flags |= XIVE_IRQ_NO_EOI;
+ }
+
return 0;
error:
irq_dispose_mapping(xc->esc_virq[prio]);
--
2.14.3
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