Il 03/07/2013 12:51, Cornelia Huck ha scritto: > On Wed, 03 Jul 2013 11:21:23 +0200 > Paolo Bonzini <[email protected]> wrote: > >> Il 03/07/2013 11:05, Paolo Bonzini ha scritto: >>> Nice idea, though I don't really like the duplication between >>> kvm_io_bus_write and kvm_io_bus_write_cookie. >>> >>> Can you make kvm_io_bus_write, and perhaps kvm_io_bus_read too, return >>> the cookie, and return -EINVAL here if the cookie is garbage? >> >> On second though---no need to return -EINVAL, you can just pass the >> cookie by value and tail-call kvm_io_bus_write. Whatever makes the s390 >> code look nicer. > > It would probably be easier to have the non-cookie functions call the > cookie functions with a negative cookie value, like the following > (untested):
That would work too, but it adds a small overhead to the non-cookie calls. If Gleb agrees with you, it is fine; otherwise, I'd prefer that one explicitly requests the cookie on input. Paolo > From 12a6e9821f1a07ecd918e927a4049263ad6f1724 Mon Sep 17 00:00:00 2001 > From: Cornelia Huck <[email protected]> > Date: Tue, 2 Jul 2013 13:30:56 +0200 > Subject: [PATCH] KVM: kvm-io: support cookies > > Add new functions kvm_io_bus_{read,write}_cookie() that allows users of > the kvm io infrastructure to use a cookie value to speed up lookup of a > device on an io bus. > > Signed-off-by: Cornelia Huck <[email protected]> > --- > include/linux/kvm_host.h | 4 +++ > virt/kvm/kvm_main.c | 82 > ++++++++++++++++++++++++++++++++++++++---------- > 2 files changed, 70 insertions(+), 16 deletions(-) > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index e3aae6d..97849fc 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -159,8 +159,12 @@ 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_read_cookie(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr, > + int len, void *val, long *cookie); > int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t > addr, > int len, struct kvm_io_device *dev); > int kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx, > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 1580dd4..21e6d7d 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -2863,11 +2863,11 @@ static int kvm_io_bus_get_first_dev(struct kvm_io_bus > *bus, > return off; > } > > -/* kvm_io_bus_write - called under kvm->slots_lock */ > -int kvm_io_bus_write(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr, > - int len, const void *val) > +/* 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; > + int idx, ret = -EOPNOTSUPP; > struct kvm_io_bus *bus; > struct kvm_io_range range; > > @@ -2877,25 +2877,50 @@ int kvm_io_bus_write(struct kvm *kvm, enum kvm_bus > bus_idx, gpa_t addr, > }; > > bus = srcu_dereference(kvm->buses[bus_idx], &kvm->srcu); > + > + /* First try the device referenced by *cookie. */ > + if ((*cookie >= 0) && (*cookie < bus->dev_count) && > + (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) > - return -EOPNOTSUPP; > + 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)) > - return 0; > + if (!kvm_iodevice_write(bus->range[idx].dev, addr, len, val)) { > + ret = 0; > + goto out; > + } > idx++; > } > + idx = -ENOENT; > +out: > + *cookie = idx; > + return ret; > +} > + > +/* kvm_io_bus_write - called under kvm->slots_lock */ > +int kvm_io_bus_write(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr, > + int len, const void *val) > +{ > + long tmp = -1; > > - return -EOPNOTSUPP; > + return kvm_io_bus_write_cookie(kvm, bus_idx, addr, len, val, &tmp); > } > > -/* 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) > +/* kvm_io_bus_read_cookie - called under kvm->slots_lock */ > +int kvm_io_bus_read_cookie(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr, > + int len, void *val, long *cookie) > { > - int idx; > + int idx, ret = -EOPNOTSUPP; > struct kvm_io_bus *bus; > struct kvm_io_range range; > > @@ -2905,18 +2930,43 @@ int kvm_io_bus_read(struct kvm *kvm, enum kvm_bus > bus_idx, gpa_t addr, > }; > > bus = srcu_dereference(kvm->buses[bus_idx], &kvm->srcu); > + > + /* First try the device referenced by *cookie. */ > + if ((*cookie >= 0) && (*cookie < bus->dev_count) && > + (kvm_io_bus_sort_cmp(&range, &bus->range[*cookie]) == 0)) > + if (!kvm_iodevice_read(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) > - return -EOPNOTSUPP; > + goto out; > > while (idx < bus->dev_count && > kvm_io_bus_sort_cmp(&range, &bus->range[idx]) == 0) { > - if (!kvm_iodevice_read(bus->range[idx].dev, addr, len, val)) > - return 0; > + if (!kvm_iodevice_read(bus->range[idx].dev, addr, len, val)) { > + ret = 0; > + goto out; > + } > idx++; > } > + idx = -ENOENT; > +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) > +{ > + long tmp = -1; > > - return -EOPNOTSUPP; > + return kvm_io_bus_read_cookie(kvm, bus_idx, addr, len, val, &tmp); > } > > /* Caller must hold slots_lock. */ > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
