From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cornelia Huck Subject: Re: [PATCH 1/2] KVM: kvm-io: support cookies Date: Wed, 3 Jul 2013 12:51:38 +0200 Message-ID: <20130703125138.400ac1ef@gondolin> References: <1372841780-29645-1-git-send-email-cornelia.huck@de.ibm.com> <1372841780-29645-2-git-send-email-cornelia.huck@de.ibm.com> <51D3E96E.5080405@redhat.com> <51D3ED13.2020408@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Cc: Gleb Natapov , Christian Borntraeger , Heiko Carstens , Martin Schwidefsky , KVM , linux-s390 To: Paolo Bonzini Return-path: Received: from e06smtp16.uk.ibm.com ([195.75.94.112]:53771 "EHLO e06smtp16.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753737Ab3GCKvt convert rfc822-to-8bit (ORCPT ); Wed, 3 Jul 2013 06:51:49 -0400 Received: from /spool/local by e06smtp16.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 3 Jul 2013 11:46:20 +0100 In-Reply-To: <51D3ED13.2020408@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Wed, 03 Jul 2013 11:21:23 +0200 Paolo Bonzini 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): >>From 12a6e9821f1a07ecd918e927a4049263ad6f1724 Mon Sep 17 00:00:00 2001 From: Cornelia Huck 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 --- 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. */ -- 1.8.2.2