KVM: PPC: Book3S HV: Add support for real mode ICP in XICS emulation

This adds an implementation of the XICS hypercalls in real mode for HV
KVM, which allows us to avoid exiting the guest MMU context on all
threads for a variety of operations such as fetching a pending
interrupt, EOI of messages, IPIs, etc.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>

1 files changed, 406 insertions, 0 deletions

diff --git a/arch/powerpc/kvm/book3s_hv_rm_xics.c b/arch/powerpc/kvm/book3s_hv_rm_xics.c
new file mode 100644
index 000000000000..b4b0082f761c
--- /dev/null
+++ b/arch/powerpc/kvm/book3s_hv_rm_xics.c
@@ -0,0 +1,406 @@
+/*
+ * Copyright 2012 Michael Ellerman, IBM Corporation.
+ * Copyright 2012 Benjamin Herrenschmidt, IBM Corporation
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License, version 2, as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/kvm_host.h>
+#include <linux/err.h>
+
+#include <asm/kvm_book3s.h>
+#include <asm/kvm_ppc.h>
+#include <asm/hvcall.h>
+#include <asm/xics.h>
+#include <asm/debug.h>
+#include <asm/synch.h>
+#include <asm/ppc-opcode.h>
+
+#include "book3s_xics.h"
+
+#define DEBUG_PASSUP
+
+static inline void rm_writeb(unsigned long paddr, u8 val)
+{
+	__asm__ __volatile__("sync; stbcix %0,0,%1"
+		: : "r" (val), "r" (paddr) : "memory");
+}
+
+static void icp_rm_set_vcpu_irq(struct kvm_vcpu *vcpu,
+				struct kvm_vcpu *this_vcpu)
+{
+	struct kvmppc_icp *this_icp = this_vcpu->arch.icp;
+	unsigned long xics_phys;
+	int cpu;
+
+	/* Mark the target VCPU as having an interrupt pending */
+	vcpu->stat.queue_intr++;
+	set_bit(BOOK3S_IRQPRIO_EXTERNAL_LEVEL, &vcpu->arch.pending_exceptions);
+
+	/* Kick self ? Just set MER and return */
+	if (vcpu == this_vcpu) {
+		mtspr(SPRN_LPCR, mfspr(SPRN_LPCR) | LPCR_MER);
+		return;
+	}
+
+	/* Check if the core is loaded, if not, too hard */
+	cpu = vcpu->cpu;
+	if (cpu < 0 || cpu >= nr_cpu_ids) {
+		this_icp->rm_action |= XICS_RM_KICK_VCPU;
+		this_icp->rm_kick_target = vcpu;
+		return;
+	}
+	/* In SMT cpu will always point to thread 0, we adjust it */
+	cpu += vcpu->arch.ptid;
+
+	/* Not too hard, then poke the target */
+	xics_phys = paca[cpu].kvm_hstate.xics_phys;
+	rm_writeb(xics_phys + XICS_MFRR, IPI_PRIORITY);
+}
+
+static void icp_rm_clr_vcpu_irq(struct kvm_vcpu *vcpu)
+{
+	/* Note: Only called on self ! */
+	clear_bit(BOOK3S_IRQPRIO_EXTERNAL_LEVEL,
+		  &vcpu->arch.pending_exceptions);
+	mtspr(SPRN_LPCR, mfspr(SPRN_LPCR) & ~LPCR_MER);
+}
+
+static inline bool icp_rm_try_update(struct kvmppc_icp *icp,
+				     union kvmppc_icp_state old,
+				     union kvmppc_icp_state new)
+{
+	struct kvm_vcpu *this_vcpu = local_paca->kvm_hstate.kvm_vcpu;
+	bool success;
+
+	/* Calculate new output value */
+	new.out_ee = (new.xisr && (new.pending_pri < new.cppr));
+
+	/* Attempt atomic update */
+	success = cmpxchg64(&icp->state.raw, old.raw, new.raw) == old.raw;
+	if (!success)
+		goto bail;
+
+	/*
+	 * Check for output state update
+	 *
+	 * Note that this is racy since another processor could be updating
+	 * the state already. This is why we never clear the interrupt output
+	 * here, we only ever set it. The clear only happens prior to doing
+	 * an update and only by the processor itself. Currently we do it
+	 * in Accept (H_XIRR) and Up_Cppr (H_XPPR).
+	 *
+	 * We also do not try to figure out whether the EE state has changed,
+	 * we unconditionally set it if the new state calls for it. The reason
+	 * for that is that we opportunistically remove the pending interrupt
+	 * flag when raising CPPR, so we need to set it back here if an
+	 * interrupt is still pending.
+	 */
+	if (new.out_ee)
+		icp_rm_set_vcpu_irq(icp->vcpu, this_vcpu);
+
+	/* Expose the state change for debug purposes */
+	this_vcpu->arch.icp->rm_dbgstate = new;
+	this_vcpu->arch.icp->rm_dbgtgt = icp->vcpu;
+
+ bail:
+	return success;
+}
+
+static inline int check_too_hard(struct kvmppc_xics *xics,
+				 struct kvmppc_icp *icp)
+{
+	return (xics->real_mode_dbg || icp->rm_action) ? H_TOO_HARD : H_SUCCESS;
+}
+
+static void icp_rm_down_cppr(struct kvmppc_xics *xics, struct kvmppc_icp *icp,
+			     u8 new_cppr)
+{
+	union kvmppc_icp_state old_state, new_state;
+	bool resend;
+
+	/*
+	 * This handles several related states in one operation:
+	 *
+	 * ICP State: Down_CPPR
+	 *
+	 * Load CPPR with new value and if the XISR is 0
+	 * then check for resends:
+	 *
+	 * ICP State: Resend
+	 *
+	 * If MFRR is more favored than CPPR, check for IPIs
+	 * and notify ICS of a potential resend. This is done
+	 * asynchronously (when used in real mode, we will have
+	 * to exit here).
+	 *
+	 * We do not handle the complete Check_IPI as documented
+	 * here. In the PAPR, this state will be used for both
+	 * Set_MFRR and Down_CPPR. However, we know that we aren't
+	 * changing the MFRR state here so we don't need to handle
+	 * the case of an MFRR causing a reject of a pending irq,
+	 * this will have been handled when the MFRR was set in the
+	 * first place.
+	 *
+	 * Thus we don't have to handle rejects, only resends.
+	 *
+	 * When implementing real mode for HV KVM, resend will lead to
+	 * a H_TOO_HARD return and the whole transaction will be handled
+	 * in virtual mode.
+	 */
+	do {
+		old_state = new_state = ACCESS_ONCE(icp->state);
+
+		/* Down_CPPR */
+		new_state.cppr = new_cppr;
+
+		/*
+		 * Cut down Resend / Check_IPI / IPI
+		 *
+		 * The logic is that we cannot have a pending interrupt
+		 * trumped by an IPI at this point (see above), so we
+		 * know that either the pending interrupt is already an
+		 * IPI (in which case we don't care to override it) or
+		 * it's either more favored than us or non existent
+		 */
+		if (new_state.mfrr < new_cppr &&
+		    new_state.mfrr <= new_state.pending_pri) {
+			new_state.pending_pri = new_state.mfrr;
+			new_state.xisr = XICS_IPI;
+		}
+
+		/* Latch/clear resend bit */
+		resend = new_state.need_resend;
+		new_state.need_resend = 0;
+
+	} while (!icp_rm_try_update(icp, old_state, new_state));
+
+	/*
+	 * Now handle resend checks. Those are asynchronous to the ICP
+	 * state update in HW (ie bus transactions) so we can handle them
+	 * separately here as well.
+	 */
+	if (resend)
+		icp->rm_action |= XICS_RM_CHECK_RESEND;
+}
+
+
+unsigned long kvmppc_rm_h_xirr(struct kvm_vcpu *vcpu)
+{
+	union kvmppc_icp_state old_state, new_state;
+	struct kvmppc_xics *xics = vcpu->kvm->arch.xics;
+	struct kvmppc_icp *icp = vcpu->arch.icp;
+	u32 xirr;
+
+	if (!xics || !xics->real_mode)
+		return H_TOO_HARD;
+
+	/* First clear the interrupt */
+	icp_rm_clr_vcpu_irq(icp->vcpu);
+
+	/*
+	 * ICP State: Accept_Interrupt
+	 *
+	 * Return the pending interrupt (if any) along with the
+	 * current CPPR, then clear the XISR & set CPPR to the
+	 * pending priority
+	 */
+	do {
+		old_state = new_state = ACCESS_ONCE(icp->state);
+
+		xirr = old_state.xisr | (((u32)old_state.cppr) << 24);
+		if (!old_state.xisr)
+			break;
+		new_state.cppr = new_state.pending_pri;
+		new_state.pending_pri = 0xff;
+		new_state.xisr = 0;
+
+	} while (!icp_rm_try_update(icp, old_state, new_state));
+
+	/* Return the result in GPR4 */
+	vcpu->arch.gpr[4] = xirr;
+
+	return check_too_hard(xics, icp);
+}
+
+int kvmppc_rm_h_ipi(struct kvm_vcpu *vcpu, unsigned long server,
+		    unsigned long mfrr)
+{
+	union kvmppc_icp_state old_state, new_state;
+	struct kvmppc_xics *xics = vcpu->kvm->arch.xics;
+	struct kvmppc_icp *icp, *this_icp = vcpu->arch.icp;
+	u32 reject;
+	bool resend;
+	bool local;
+
+	if (!xics || !xics->real_mode)
+		return H_TOO_HARD;
+
+	local = this_icp->server_num == server;
+	if (local)
+		icp = this_icp;
+	else
+		icp = kvmppc_xics_find_server(vcpu->kvm, server);
+	if (!icp)
+		return H_PARAMETER;
+
+	/*
+	 * ICP state: Set_MFRR
+	 *
+	 * If the CPPR is more favored than the new MFRR, then
+	 * nothing needs to be done as there can be no XISR to
+	 * reject.
+	 *
+	 * If the CPPR is less favored, then we might be replacing
+	 * an interrupt, and thus need to possibly reject it as in
+	 *
+	 * ICP state: Check_IPI
+	 */
+	do {
+		old_state = new_state = ACCESS_ONCE(icp->state);
+
+		/* Set_MFRR */
+		new_state.mfrr = mfrr;
+
+		/* Check_IPI */
+		reject = 0;
+		resend = false;
+		if (mfrr < new_state.cppr) {
+			/* Reject a pending interrupt if not an IPI */
+			if (mfrr <= new_state.pending_pri)
+				reject = new_state.xisr;
+			new_state.pending_pri = mfrr;
+			new_state.xisr = XICS_IPI;
+		}
+
+		if (mfrr > old_state.mfrr && mfrr > new_state.cppr) {
+			resend = new_state.need_resend;
+			new_state.need_resend = 0;
+		}
+	} while (!icp_rm_try_update(icp, old_state, new_state));
+
+	/* Pass rejects to virtual mode */
+	if (reject && reject != XICS_IPI) {
+		this_icp->rm_action |= XICS_RM_REJECT;
+		this_icp->rm_reject = reject;
+	}
+
+	/* Pass resends to virtual mode */
+	if (resend)
+		this_icp->rm_action |= XICS_RM_CHECK_RESEND;
+
+	return check_too_hard(xics, this_icp);
+}
+
+int kvmppc_rm_h_cppr(struct kvm_vcpu *vcpu, unsigned long cppr)
+{
+	union kvmppc_icp_state old_state, new_state;
+	struct kvmppc_xics *xics = vcpu->kvm->arch.xics;
+	struct kvmppc_icp *icp = vcpu->arch.icp;
+	u32 reject;
+
+	if (!xics || !xics->real_mode)
+		return H_TOO_HARD;
+
+	/*
+	 * ICP State: Set_CPPR
+	 *
+	 * We can safely compare the new value with the current
+	 * value outside of the transaction as the CPPR is only
+	 * ever changed by the processor on itself
+	 */
+	if (cppr > icp->state.cppr) {
+		icp_rm_down_cppr(xics, icp, cppr);
+		goto bail;
+	} else if (cppr == icp->state.cppr)
+		return H_SUCCESS;
+
+	/*
+	 * ICP State: Up_CPPR
+	 *
+	 * The processor is raising its priority, this can result
+	 * in a rejection of a pending interrupt:
+	 *
+	 * ICP State: Reject_Current
+	 *
+	 * We can remove EE from the current processor, the update
+	 * transaction will set it again if needed
+	 */
+	icp_rm_clr_vcpu_irq(icp->vcpu);
+
+	do {
+		old_state = new_state = ACCESS_ONCE(icp->state);
+
+		reject = 0;
+		new_state.cppr = cppr;
+
+		if (cppr <= new_state.pending_pri) {
+			reject = new_state.xisr;
+			new_state.xisr = 0;
+			new_state.pending_pri = 0xff;
+		}
+
+	} while (!icp_rm_try_update(icp, old_state, new_state));
+
+	/* Pass rejects to virtual mode */
+	if (reject && reject != XICS_IPI) {
+		icp->rm_action |= XICS_RM_REJECT;
+		icp->rm_reject = reject;
+	}
+ bail:
+	return check_too_hard(xics, icp);
+}
+
+int kvmppc_rm_h_eoi(struct kvm_vcpu *vcpu, unsigned long xirr)
+{
+	struct kvmppc_xics *xics = vcpu->kvm->arch.xics;
+	struct kvmppc_icp *icp = vcpu->arch.icp;
+	struct kvmppc_ics *ics;
+	struct ics_irq_state *state;
+	u32 irq = xirr & 0x00ffffff;
+	u16 src;
+
+	if (!xics || !xics->real_mode)
+		return H_TOO_HARD;
+
+	/*
+	 * ICP State: EOI
+	 *
+	 * Note: If EOI is incorrectly used by SW to lower the CPPR
+	 * value (ie more favored), we do not check for rejection of
+	 * a pending interrupt, this is a SW error and PAPR sepcifies
+	 * that we don't have to deal with it.
+	 *
+	 * The sending of an EOI to the ICS is handled after the
+	 * CPPR update
+	 *
+	 * ICP State: Down_CPPR which we handle
+	 * in a separate function as it's shared with H_CPPR.
+	 */
+	icp_rm_down_cppr(xics, icp, xirr >> 24);
+
+	/* IPIs have no EOI */
+	if (irq == XICS_IPI)
+		goto bail;
+	/*
+	 * EOI handling: If the interrupt is still asserted, we need to
+	 * resend it. We can take a lockless "peek" at the ICS state here.
+	 *
+	 * "Message" interrupts will never have "asserted" set
+	 */
+	ics = kvmppc_xics_find_ics(xics, irq, &src);
+	if (!ics)
+		goto bail;
+	state = &ics->irq_state[src];
+
+	/* Still asserted, resend it, we make it look like a reject */
+	if (state->asserted) {
+		icp->rm_action |= XICS_RM_REJECT;
+		icp->rm_reject = irq;
+	}
+ bail:
+	return check_too_hard(xics, icp);
+}