From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoffer Dall Subject: Re: [PATCH v5 16/22] KVM: arm64: vgic-its: Add infrastructure for table lookup Date: Wed, 3 May 2017 10:01:58 +0200 Message-ID: <20170503080158.GA8452@cbox> References: <1492164934-988-1-git-send-email-eric.auger@redhat.com> <1492164934-988-17-git-send-email-eric.auger@redhat.com> <20170430193555.GB1670@lvm> <303f2981-489e-ec38-ebaf-40d65429d820@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Christoffer Dall , eric.auger.pro@gmail.com, marc.zyngier@arm.com, andre.przywara@arm.com, vijayak@caviumnetworks.com, Vijaya.Kumar@cavium.com, peter.maydell@linaro.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, Prasun.Kapoor@cavium.com, drjones@redhat.com, pbonzini@redhat.com, dgilbert@redhat.com, quintela@redhat.com To: Auger Eric Return-path: Received: from mail-wm0-f46.google.com ([74.125.82.46]:33535 "EHLO mail-wm0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751031AbdECICB (ORCPT ); Wed, 3 May 2017 04:02:01 -0400 Received: by mail-wm0-f46.google.com with SMTP id n198so20085276wmg.0 for ; Wed, 03 May 2017 01:02:00 -0700 (PDT) Content-Disposition: inline In-Reply-To: <303f2981-489e-ec38-ebaf-40d65429d820@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Wed, May 03, 2017 at 08:53:36AM +0200, Auger Eric wrote: > Hi Christoffer, > > On 30/04/2017 21:35, Christoffer Dall wrote: > > On Fri, Apr 14, 2017 at 12:15:28PM +0200, Eric Auger wrote: > >> Add a generic lookup_table() helper whose role consists in > >> scanning a contiguous table located in guest RAM and applying > >> a callback on each entry. Entries can be handled as linked lists > >> since the callback may return an offset to the next entry and > >> also tell that an entry is the last one. > >> > >> Helper functions also are added to compute the device/event ID > >> offset to the next DTE/ITE. > >> > >> compute_next_devid_offset, compute_next_eventid_offset and > >> lookup_table will become static in subsequent patches > >> > >> Signed-off-by: Eric Auger > >> > >> --- > >> v4 -> v5: > >> - use kvm_read_guest > >> > >> v3 -> v4: > >> - remove static to avoid compilation warning > >> - correct size computation in looup_table() > >> - defines now encode the number of bits used for devid and eventid offsets > >> - use BIT() - 1 to encode the max offets > >> --- > >> virt/kvm/arm/vgic/vgic-its.c | 93 ++++++++++++++++++++++++++++++++++++++++++++ > >> 1 file changed, 93 insertions(+) > >> > >> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c > >> index 56c5123..c22b35d 100644 > >> --- a/virt/kvm/arm/vgic/vgic-its.c > >> +++ b/virt/kvm/arm/vgic/vgic-its.c > >> @@ -195,6 +195,8 @@ static struct its_ite *find_ite(struct vgic_its *its, u32 device_id, > >> > >> #define VITS_TYPER_IDBITS 16 > >> #define VITS_TYPER_DEVBITS 16 > >> +#define VITS_DTE_MAX_DEVID_OFFSET (BIT(14) - 1) > >> +#define VITS_ITE_MAX_EVENTID_OFFSET (BIT(16) - 1) > >> > >> /* > >> * Finds and returns a collection in the ITS collection table. > >> @@ -1674,6 +1676,97 @@ int vgic_its_attr_regs_access(struct kvm_device *dev, > >> return ret; > >> } > >> > >> +u32 compute_next_devid_offset(struct list_head *h, struct its_device *dev) > >> +{ > >> + struct list_head *e = &dev->dev_list; > >> + struct its_device *next; > >> + u32 next_offset; > >> + > >> + if (e->next == h) > >> + return 0; > >> + next = list_entry(e->next, struct its_device, dev_list); > >> + next_offset = next->device_id - dev->device_id; > >> + > >> + return min_t(u32, next_offset, VITS_DTE_MAX_DEVID_OFFSET); > >> +} > >> + > >> +u32 compute_next_eventid_offset(struct list_head *h, struct its_ite *ite) > >> +{ > >> + struct list_head *e = &ite->ite_list; > >> + struct its_ite *next; > >> + u32 next_offset; > >> + > >> + if (e->next == h) > >> + return 0; > >> + next = list_entry(e->next, struct its_ite, ite_list); > >> + next_offset = next->event_id - ite->event_id; > >> + > >> + return min_t(u32, next_offset, VITS_ITE_MAX_EVENTID_OFFSET); > >> +} > >> + > >> +/** > >> + * entry_fn_t - Callback called on a table entry restore path > >> + * @its: its handle > >> + * @id: id of the entry > >> + * @entry: pointer to the entry > >> + * @opaque: pointer to an opaque data > >> + * @next_offset: minimal ID offset to the next entry. 0 if this > >> + * entry is the last one, 1 if the entry is invalid, >= 1 if an > > > > eh, also, did you mean -1 if the entry is invalid? > no in case the entry is invalid, we tell the caller that it must inspect > the next entry, hence the next_offset = +1. hmm, but you say aftterwards that >= 1 if an entry's next_offset field was truly decoded, so this is confusing. Perhaps it would make more sense to get rid of the parameter entirely and change the return value to say: Return: < 0 on error, 0 if the entry was the last one, and > 0 to indicate the offset to the next entry that must be processed when scanning a table. Note that we return 1 for an invalid entry, because scanning a table in this case simply requires us looking at the next entry, but we may return >= to 1 if we found a valid entry and decoded the next field in the entry. What do you think? Thanks, -Christoffer From mboxrd@z Thu Jan 1 00:00:00 1970 From: cdall@linaro.org (Christoffer Dall) Date: Wed, 3 May 2017 10:01:58 +0200 Subject: [PATCH v5 16/22] KVM: arm64: vgic-its: Add infrastructure for table lookup In-Reply-To: <303f2981-489e-ec38-ebaf-40d65429d820@redhat.com> References: <1492164934-988-1-git-send-email-eric.auger@redhat.com> <1492164934-988-17-git-send-email-eric.auger@redhat.com> <20170430193555.GB1670@lvm> <303f2981-489e-ec38-ebaf-40d65429d820@redhat.com> Message-ID: <20170503080158.GA8452@cbox> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, May 03, 2017 at 08:53:36AM +0200, Auger Eric wrote: > Hi Christoffer, > > On 30/04/2017 21:35, Christoffer Dall wrote: > > On Fri, Apr 14, 2017 at 12:15:28PM +0200, Eric Auger wrote: > >> Add a generic lookup_table() helper whose role consists in > >> scanning a contiguous table located in guest RAM and applying > >> a callback on each entry. Entries can be handled as linked lists > >> since the callback may return an offset to the next entry and > >> also tell that an entry is the last one. > >> > >> Helper functions also are added to compute the device/event ID > >> offset to the next DTE/ITE. > >> > >> compute_next_devid_offset, compute_next_eventid_offset and > >> lookup_table will become static in subsequent patches > >> > >> Signed-off-by: Eric Auger > >> > >> --- > >> v4 -> v5: > >> - use kvm_read_guest > >> > >> v3 -> v4: > >> - remove static to avoid compilation warning > >> - correct size computation in looup_table() > >> - defines now encode the number of bits used for devid and eventid offsets > >> - use BIT() - 1 to encode the max offets > >> --- > >> virt/kvm/arm/vgic/vgic-its.c | 93 ++++++++++++++++++++++++++++++++++++++++++++ > >> 1 file changed, 93 insertions(+) > >> > >> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c > >> index 56c5123..c22b35d 100644 > >> --- a/virt/kvm/arm/vgic/vgic-its.c > >> +++ b/virt/kvm/arm/vgic/vgic-its.c > >> @@ -195,6 +195,8 @@ static struct its_ite *find_ite(struct vgic_its *its, u32 device_id, > >> > >> #define VITS_TYPER_IDBITS 16 > >> #define VITS_TYPER_DEVBITS 16 > >> +#define VITS_DTE_MAX_DEVID_OFFSET (BIT(14) - 1) > >> +#define VITS_ITE_MAX_EVENTID_OFFSET (BIT(16) - 1) > >> > >> /* > >> * Finds and returns a collection in the ITS collection table. > >> @@ -1674,6 +1676,97 @@ int vgic_its_attr_regs_access(struct kvm_device *dev, > >> return ret; > >> } > >> > >> +u32 compute_next_devid_offset(struct list_head *h, struct its_device *dev) > >> +{ > >> + struct list_head *e = &dev->dev_list; > >> + struct its_device *next; > >> + u32 next_offset; > >> + > >> + if (e->next == h) > >> + return 0; > >> + next = list_entry(e->next, struct its_device, dev_list); > >> + next_offset = next->device_id - dev->device_id; > >> + > >> + return min_t(u32, next_offset, VITS_DTE_MAX_DEVID_OFFSET); > >> +} > >> + > >> +u32 compute_next_eventid_offset(struct list_head *h, struct its_ite *ite) > >> +{ > >> + struct list_head *e = &ite->ite_list; > >> + struct its_ite *next; > >> + u32 next_offset; > >> + > >> + if (e->next == h) > >> + return 0; > >> + next = list_entry(e->next, struct its_ite, ite_list); > >> + next_offset = next->event_id - ite->event_id; > >> + > >> + return min_t(u32, next_offset, VITS_ITE_MAX_EVENTID_OFFSET); > >> +} > >> + > >> +/** > >> + * entry_fn_t - Callback called on a table entry restore path > >> + * @its: its handle > >> + * @id: id of the entry > >> + * @entry: pointer to the entry > >> + * @opaque: pointer to an opaque data > >> + * @next_offset: minimal ID offset to the next entry. 0 if this > >> + * entry is the last one, 1 if the entry is invalid, >= 1 if an > > > > eh, also, did you mean -1 if the entry is invalid? > no in case the entry is invalid, we tell the caller that it must inspect > the next entry, hence the next_offset = +1. hmm, but you say aftterwards that >= 1 if an entry's next_offset field was truly decoded, so this is confusing. Perhaps it would make more sense to get rid of the parameter entirely and change the return value to say: Return: < 0 on error, 0 if the entry was the last one, and > 0 to indicate the offset to the next entry that must be processed when scanning a table. Note that we return 1 for an invalid entry, because scanning a table in this case simply requires us looking at the next entry, but we may return >= to 1 if we found a valid entry and decoded the next field in the entry. What do you think? Thanks, -Christoffer