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

[Cornelia Huck]

On Mon, 4 Mar 2013 21:07:41 -0300
Marcelo Tosatti <address@hidden> 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 <address@hidden>
> > ---
> >  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 <address@hidden>
Date:   Tue Feb 26 17:05:01 2013 +0100

    virtio-ccw: ioeventfd: use cookies
    
    Signed-off-by: Cornelia Huck <address@hidden>

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)