From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marc Zyngier Subject: Re: [PATCH v4 17/22] KVM: arm64: ITS: Add infrastructure for table lookup Date: Sun, 09 Apr 2017 11:36:14 +0100 Message-ID: <864lxxc1gh.fsf@arm.com> References: <1490607072-21610-1-git-send-email-eric.auger@redhat.com> <1490607072-21610-18-git-send-email-eric.auger@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org, Prasun.Kapoor@cavium.com, vijayak@caviumnetworks.com, andre.przywara@arm.com, quintela@redhat.com, dgilbert@redhat.com, Vijaya.Kumar@cavium.com, linux-arm-kernel@lists.infradead.org, pbonzini@redhat.com, kvmarm@lists.cs.columbia.edu, eric.auger.pro@gmail.com To: Eric Auger Return-path: In-Reply-To: <1490607072-21610-18-git-send-email-eric.auger@redhat.com> (Eric Auger's message of "Mon, 27 Mar 2017 11:31:07 +0200") List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu List-Id: kvm.vger.kernel.org On Mon, Mar 27 2017 at 10:31:07 AM, 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 > > --- > > 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 | 107 +++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 107 insertions(+) > > diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c > index 7364b7d..8eaeba4 100644 > --- a/virt/kvm/arm/vgic/vgic-its.c > +++ b/virt/kvm/arm/vgic/vgic-its.c > @@ -184,6 +184,8 @@ static struct its_ite *find_ite(struct vgic_its *its, u32 device_id, > #define VITS_ESZ 8 > #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. > @@ -1686,6 +1688,111 @@ 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 > + * @addr: kernel VA of 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 > + * entry's next_offset field was truly decoded > + * > + * Return: < 0 on error, 0 otherwise > + */ > +typedef int (*entry_fn_t)(struct vgic_its *its, u32 id, void *addr, > + void *opaque, u32 *next_offset); > + > +/** > + * lookup_table - scans a contiguous table in guest RAM and applies a function > + * to each entry > + * > + * @its: its handle > + * @base: base gpa of the table > + * @size: size of the table in bytes > + * @esz: entry size in bytes > + * @start_id: first entry's ID > + * @fn: function to apply on each entry > + * > + * Return: < 0 on error, 1 if last element identified, 0 otherwise > + */ > +int lookup_table(struct vgic_its *its, gpa_t base, int size, int esz, > + int start_id, entry_fn_t fn, void *opaque) > +{ > + gpa_t gpa = base, top = base + size - 1; > + unsigned long len = size; > + int ret, seg, offset = offset_in_page(gpa); > + gfn_t gfn = gpa >> PAGE_SHIFT; > + u32 id = start_id + (gpa - base)/esz; > + struct kvm *kvm = its->dev->kvm; > + kvm_pfn_t pfn; > + > + while ((seg = next_segment(len, offset)) != 0) { > + u32 next_offset; > + bool writeable; > + void *addr; > + > + pfn = gfn_to_pfn_prot(kvm, gfn, true, &writeable); > + if (is_error_noslot_pfn(pfn)) > + return -EINVAL; > + addr = phys_to_virt((u64)pfn << PAGE_SHIFT); > + addr += offset; Why do we use the kernel mapping here? I'd have expected the use of kvm_read_guest and co rather than directly accessing the memory. What locks do we hold to ensure that the page cannot be evicted behind our back? > + > + while (seg > 0) { > + size_t byte_offset; > + > + ret = fn(its, id, addr, opaque, &next_offset); > + if (ret < 0 || (!ret && !next_offset)) > + goto out; > + > + byte_offset = next_offset * esz; > + > + id += next_offset; > + gpa += byte_offset; > + addr += byte_offset; > + seg -= byte_offset; > + } > + kvm_release_pfn_clean(pfn); > + > + len = top - gpa + 1; > + offset = offset_in_page(gpa); > + gfn = gpa >> PAGE_SHIFT; > + id = start_id + (gpa - base)/esz; > + } > + return 0; > +out: > + kvm_release_pfn_clean(pfn); > + return (ret < 0 ? ret : 1); > +} > + > /** > * vgic_its_flush_pending_tables - Flush the pending tables into guest RAM > */ Thanks, M. -- Jazz is not dead. It just smells funny. From mboxrd@z Thu Jan 1 00:00:00 1970 From: marc.zyngier@arm.com (Marc Zyngier) Date: Sun, 09 Apr 2017 11:36:14 +0100 Subject: [PATCH v4 17/22] KVM: arm64: ITS: Add infrastructure for table lookup In-Reply-To: <1490607072-21610-18-git-send-email-eric.auger@redhat.com> (Eric Auger's message of "Mon, 27 Mar 2017 11:31:07 +0200") References: <1490607072-21610-1-git-send-email-eric.auger@redhat.com> <1490607072-21610-18-git-send-email-eric.auger@redhat.com> Message-ID: <864lxxc1gh.fsf@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Mon, Mar 27 2017 at 10:31:07 AM, 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 > > --- > > 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 | 107 +++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 107 insertions(+) > > diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c > index 7364b7d..8eaeba4 100644 > --- a/virt/kvm/arm/vgic/vgic-its.c > +++ b/virt/kvm/arm/vgic/vgic-its.c > @@ -184,6 +184,8 @@ static struct its_ite *find_ite(struct vgic_its *its, u32 device_id, > #define VITS_ESZ 8 > #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. > @@ -1686,6 +1688,111 @@ 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 > + * @addr: kernel VA of 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 > + * entry's next_offset field was truly decoded > + * > + * Return: < 0 on error, 0 otherwise > + */ > +typedef int (*entry_fn_t)(struct vgic_its *its, u32 id, void *addr, > + void *opaque, u32 *next_offset); > + > +/** > + * lookup_table - scans a contiguous table in guest RAM and applies a function > + * to each entry > + * > + * @its: its handle > + * @base: base gpa of the table > + * @size: size of the table in bytes > + * @esz: entry size in bytes > + * @start_id: first entry's ID > + * @fn: function to apply on each entry > + * > + * Return: < 0 on error, 1 if last element identified, 0 otherwise > + */ > +int lookup_table(struct vgic_its *its, gpa_t base, int size, int esz, > + int start_id, entry_fn_t fn, void *opaque) > +{ > + gpa_t gpa = base, top = base + size - 1; > + unsigned long len = size; > + int ret, seg, offset = offset_in_page(gpa); > + gfn_t gfn = gpa >> PAGE_SHIFT; > + u32 id = start_id + (gpa - base)/esz; > + struct kvm *kvm = its->dev->kvm; > + kvm_pfn_t pfn; > + > + while ((seg = next_segment(len, offset)) != 0) { > + u32 next_offset; > + bool writeable; > + void *addr; > + > + pfn = gfn_to_pfn_prot(kvm, gfn, true, &writeable); > + if (is_error_noslot_pfn(pfn)) > + return -EINVAL; > + addr = phys_to_virt((u64)pfn << PAGE_SHIFT); > + addr += offset; Why do we use the kernel mapping here? I'd have expected the use of kvm_read_guest and co rather than directly accessing the memory. What locks do we hold to ensure that the page cannot be evicted behind our back? > + > + while (seg > 0) { > + size_t byte_offset; > + > + ret = fn(its, id, addr, opaque, &next_offset); > + if (ret < 0 || (!ret && !next_offset)) > + goto out; > + > + byte_offset = next_offset * esz; > + > + id += next_offset; > + gpa += byte_offset; > + addr += byte_offset; > + seg -= byte_offset; > + } > + kvm_release_pfn_clean(pfn); > + > + len = top - gpa + 1; > + offset = offset_in_page(gpa); > + gfn = gpa >> PAGE_SHIFT; > + id = start_id + (gpa - base)/esz; > + } > + return 0; > +out: > + kvm_release_pfn_clean(pfn); > + return (ret < 0 ? ret : 1); > +} > + > /** > * vgic_its_flush_pending_tables - Flush the pending tables into guest RAM > */ Thanks, M. -- Jazz is not dead. It just smells funny.