Re: [Qemu-devel] [PATCH v5 6/6] KVM: s390: Wire up ioeventfd.

[Cornelia Huck <cornelia.huck@de.ibm.com>]

On Mon, 4 Mar 2013 21:07:41 -0300
Marcelo Tosatti <mtosatti@redhat.com> wrote:

> On Thu, Feb 28, 2013 at 12:33:21PM +0100, Cornelia Huck wrote:
> > Enable ioeventfd support on s390 and hook up diagnose 500 virtio-ccw
> > notifications.
> > 
> > Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
> > ---
> >  arch/s390/kvm/Kconfig    |  1 +
> >  arch/s390/kvm/Makefile   |  2 +-
> >  arch/s390/kvm/diag.c     | 26 ++++++++++++++++++++++++++
> >  arch/s390/kvm/kvm-s390.c |  1 +
> >  4 files changed, 29 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/s390/kvm/Kconfig b/arch/s390/kvm/Kconfig
> > index b58dd86..3c43e30 100644
> > --- a/arch/s390/kvm/Kconfig
> > +++ b/arch/s390/kvm/Kconfig
> > @@ -22,6 +22,7 @@ config KVM
> >  	select PREEMPT_NOTIFIERS
> >  	select ANON_INODES
> >  	select HAVE_KVM_CPU_RELAX_INTERCEPT
> > +	select HAVE_KVM_EVENTFD
> >  	---help---
> >  	  Support hosting paravirtualized guest machines using the SIE
> >  	  virtualization capability on the mainframe. This should work
> > diff --git a/arch/s390/kvm/Makefile b/arch/s390/kvm/Makefile
> > index 3975722..8fe9d65 100644
> > --- a/arch/s390/kvm/Makefile
> > +++ b/arch/s390/kvm/Makefile
> > @@ -6,7 +6,7 @@
> >  # it under the terms of the GNU General Public License (version 2 only)
> >  # as published by the Free Software Foundation.
> >  
> > -common-objs = $(addprefix ../../../virt/kvm/, kvm_main.o)
> > +common-objs = $(addprefix ../../../virt/kvm/, kvm_main.o eventfd.o)
> >  
> >  ccflags-y := -Ivirt/kvm -Iarch/s390/kvm
> >  
> > diff --git a/arch/s390/kvm/diag.c b/arch/s390/kvm/diag.c
> > index a390687..1c01a99 100644
> > --- a/arch/s390/kvm/diag.c
> > +++ b/arch/s390/kvm/diag.c
> > @@ -13,6 +13,7 @@
> >  
> >  #include <linux/kvm.h>
> >  #include <linux/kvm_host.h>
> > +#include <asm/virtio-ccw.h>
> >  #include "kvm-s390.h"
> >  #include "trace.h"
> >  #include "trace-s390.h"
> > @@ -104,6 +105,29 @@ static int __diag_ipl_functions(struct kvm_vcpu *vcpu)
> >  	return -EREMOTE;
> >  }
> >  
> > +static int __diag_virtio_hypercall(struct kvm_vcpu *vcpu)
> > +{
> > +	int ret, idx;
> > +
> > +	/* No virtio-ccw notification? Get out quickly. */
> > +	if (!vcpu->kvm->arch.css_support ||
> > +	    (vcpu->run->s.regs.gprs[1] != KVM_S390_VIRTIO_CCW_NOTIFY))
> > +		return -EOPNOTSUPP;
> > +
> > +	idx = srcu_read_lock(&vcpu->kvm->srcu);
> > +	/*
> > +	 * The layout is as follows:
> > +	 * - gpr 2 contains the subchannel id (passed as addr)
> > +	 * - gpr 3 contains the virtqueue index (passed as datamatch)
> > +	 */
> > +	ret = kvm_io_bus_write(vcpu->kvm, KVM_VIRTIO_CCW_NOTIFY_BUS,
> > +				vcpu->run->s.regs.gprs[2],
> > +				8, &vcpu->run->s.regs.gprs[3]);
> > +	srcu_read_unlock(&vcpu->kvm->srcu, idx);
> > +	/* kvm_io_bus_write returns -EOPNOTSUPP if it found no match. */
> > +	return ret < 0 ? ret : 0;
> > +}
> > +
> 
> What about the cookie?

This is the not-performance-optimized version which went through our
testing and which I'd like to see applied. I also have a not-yet-tested
patch that adds cookie support (see below), but I'd like to postpone
this to 3.10.

commit 8fce4a8a3478252f7ee2eb74d2732673f5911120
Author: Cornelia Huck <cornelia.huck@de.ibm.com>
Date:   Tue Feb 26 17:05:01 2013 +0100

    virtio-ccw: ioeventfd: use cookies
    
    Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>

diff --git a/arch/s390/kvm/diag.c b/arch/s390/kvm/diag.c
index 1c01a99..bd2a013 100644
--- a/arch/s390/kvm/diag.c
+++ b/arch/s390/kvm/diag.c
@@ -108,22 +108,29 @@ static int __diag_ipl_functions(struct kvm_vcpu *vcpu)
 static int __diag_virtio_hypercall(struct kvm_vcpu *vcpu)
 {
 	int ret, idx;
+	long cookie;
 
 	/* No virtio-ccw notification? Get out quickly. */
 	if (!vcpu->kvm->arch.css_support ||
 	    (vcpu->run->s.regs.gprs[1] != KVM_S390_VIRTIO_CCW_NOTIFY))
 		return -EOPNOTSUPP;
 
+	cookie = vcpu->run->s.regs.gprs[4];
 	idx = srcu_read_lock(&vcpu->kvm->srcu);
 	/*
 	 * The layout is as follows:
 	 * - gpr 2 contains the subchannel id (passed as addr)
 	 * - gpr 3 contains the virtqueue index (passed as datamatch)
+	 * - gpr 4 contains the index on the bus (optionally)
 	 */
-	ret = kvm_io_bus_write(vcpu->kvm, KVM_VIRTIO_CCW_NOTIFY_BUS,
-				vcpu->run->s.regs.gprs[2],
-				8, &vcpu->run->s.regs.gprs[3]);
+	ret = kvm_io_bus_write_cookie(vcpu->kvm, KVM_VIRTIO_CCW_NOTIFY_BUS,
+				      vcpu->run->s.regs.gprs[2],
+				      8, &vcpu->run->s.regs.gprs[3],
+				      &cookie);
 	srcu_read_unlock(&vcpu->kvm->srcu, idx);
+	if (!ret)
+		/* Return cookie in gpr 2. */
+		vcpu->run->s.regs.gprs[2] = cookie;
 	/* kvm_io_bus_write returns -EOPNOTSUPP if it found no match. */
 	return ret < 0 ? ret : 0;
 }
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 206247f..2f65a3a 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -154,6 +154,8 @@ enum kvm_bus {
 
 int kvm_io_bus_write(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
 		     int len, const void *val);
+int kvm_io_bus_write_cookie(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
+			    int len, const void *val, long *cookie);
 int kvm_io_bus_read(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr, int len,
 		    void *val);
 int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 7c188a3..b77ea5f 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2710,6 +2710,51 @@ int kvm_io_bus_write(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
 	return -EOPNOTSUPP;
 }
 
+/* kvm_io_bus_write_cookie - called under kvm->slots_lock */
+int kvm_io_bus_write_cookie(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
+			    int len, const void *val, long *cookie)
+{
+	int idx, ret = -EOPNOTSUPP;
+	struct kvm_io_bus *bus;
+	struct kvm_io_range range;
+
+	range = (struct kvm_io_range) {
+		.addr = addr,
+		.len = len,
+	};
+
+	if (!cookie)
+		return -EINVAL;
+
+	bus = srcu_dereference(kvm->buses[bus_idx], &kvm->srcu);
+
+	/* First try the device referenced by *cookie. */
+	if (kvm_io_bus_sort_cmp(&range, &bus->range[*cookie]) == 0)
+		if (!kvm_iodevice_write(bus->range[*cookie].dev, addr, len,
+					val))
+			return 0;
+
+	/*
+	 * *cookie contained garbage; fall back to search and return the
+	 * correct value in *cookie.
+	 */
+	idx = kvm_io_bus_get_first_dev(bus, addr, len);
+	if (idx < 0)
+		goto out;
+
+	while (idx < bus->dev_count &&
+		kvm_io_bus_sort_cmp(&range, &bus->range[idx]) == 0) {
+		if (!kvm_iodevice_write(bus->range[idx].dev, addr, len, val)) {
+			ret = 0;
+			goto out;
+		}
+		idx++;
+	}
+out:
+	*cookie = idx;
+	return ret;
+}
+
 /* kvm_io_bus_read - called under kvm->slots_lock */
 int kvm_io_bus_read(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
 		    int len, void *val)