| Message ID | 20170604115737.GA9464@cbox (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Sun, Jun 04, 2017 at 01:57:37PM +0200, Christoffer Dall wrote: > On Sun, Jun 04, 2017 at 10:15:57AM +0200, Andrew Jones wrote: > > On Tue, May 23, 2017 at 10:43:29AM +0200, Christoffer Dall wrote: > > > On Mon, May 22, 2017 at 04:30:22PM +0100, Marc Zyngier wrote: > > > > On 16/05/17 11:04, Christoffer Dall wrote: > > > > > We don't need to stop a specific VCPU when changing the active state, > > > > > because private IRQs can only be modified by a running VCPU for the > > > > > VCPU itself and it is therefore already stopped. > > > > > > > > > > However, it is also possible for two VCPUs to be modifying the active > > > > > state of SPIs at the same time, which can cause the thread being stuck > > > > > in the loop that checks other VCPU threads for a potentially very long > > > > > time, or to modify the active state of a running VCPU. Fix this by > > > > > serializing all accesses to setting and clearing the active state of > > > > > interrupts using the KVM mutex. > > > > > > > > > > Reported-by: Andrew Jones <drjones@redhat.com> > > > > > Signed-off-by: Christoffer Dall <cdall@linaro.org> > > > > > --- > > > > > arch/arm/include/asm/kvm_host.h | 2 -- > > > > > arch/arm64/include/asm/kvm_host.h | 2 -- > > > > > virt/kvm/arm/arm.c | 20 ++++---------------- > > > > > virt/kvm/arm/vgic/vgic-mmio.c | 18 ++++++++++-------- > > > > > virt/kvm/arm/vgic/vgic.c | 11 ++++++----- > > > > > 5 files changed, 20 insertions(+), 33 deletions(-) > > > > > > > > > > diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h > > > > > index f0e6657..12274d4 100644 > > > > > --- a/arch/arm/include/asm/kvm_host.h > > > > > +++ b/arch/arm/include/asm/kvm_host.h > > > > > @@ -233,8 +233,6 @@ struct kvm_vcpu *kvm_arm_get_running_vcpu(void); > > > > > struct kvm_vcpu __percpu **kvm_get_running_vcpus(void); > > > > > void kvm_arm_halt_guest(struct kvm *kvm); > > > > > void kvm_arm_resume_guest(struct kvm *kvm); > > > > > -void kvm_arm_halt_vcpu(struct kvm_vcpu *vcpu); > > > > > -void kvm_arm_resume_vcpu(struct kvm_vcpu *vcpu); > > > > > > > > > > int kvm_arm_copy_coproc_indices(struct kvm_vcpu *vcpu, u64 __user *uindices); > > > > > unsigned long kvm_arm_num_coproc_regs(struct kvm_vcpu *vcpu); > > > > > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h > > > > > index 5e19165..32cbe8a 100644 > > > > > --- a/arch/arm64/include/asm/kvm_host.h > > > > > +++ b/arch/arm64/include/asm/kvm_host.h > > > > > @@ -333,8 +333,6 @@ struct kvm_vcpu *kvm_arm_get_running_vcpu(void); > > > > > struct kvm_vcpu * __percpu *kvm_get_running_vcpus(void); > > > > > void kvm_arm_halt_guest(struct kvm *kvm); > > > > > void kvm_arm_resume_guest(struct kvm *kvm); > > > > > -void kvm_arm_halt_vcpu(struct kvm_vcpu *vcpu); > > > > > -void kvm_arm_resume_vcpu(struct kvm_vcpu *vcpu); > > > > > > > > > > u64 __kvm_call_hyp(void *hypfn, ...); > > > > > #define kvm_call_hyp(f, ...) __kvm_call_hyp(kvm_ksym_ref(f), ##__VA_ARGS__) > > > > > diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c > > > > > index 3417e18..3c387fd 100644 > > > > > --- a/virt/kvm/arm/arm.c > > > > > +++ b/virt/kvm/arm/arm.c > > > > > @@ -539,27 +539,15 @@ void kvm_arm_halt_guest(struct kvm *kvm) > > > > > kvm_make_all_cpus_request(kvm, KVM_REQ_VCPU_EXIT); > > > > > } > > > > > > > > > > -void kvm_arm_halt_vcpu(struct kvm_vcpu *vcpu) > > > > > -{ > > > > > - vcpu->arch.pause = true; > > > > > - kvm_vcpu_kick(vcpu); > > > > > -} > > > > > - > > > > > -void kvm_arm_resume_vcpu(struct kvm_vcpu *vcpu) > > > > > -{ > > > > > - struct swait_queue_head *wq = kvm_arch_vcpu_wq(vcpu); > > > > > - > > > > > - vcpu->arch.pause = false; > > > > > - swake_up(wq); > > > > > -} > > > > > - > > > > > void kvm_arm_resume_guest(struct kvm *kvm) > > > > > { > > > > > int i; > > > > > struct kvm_vcpu *vcpu; > > > > > > > > > > - kvm_for_each_vcpu(i, vcpu, kvm) > > > > > - kvm_arm_resume_vcpu(vcpu); > > > > > + kvm_for_each_vcpu(i, vcpu, kvm) { > > > > > + vcpu->arch.pause = false; > > > > > + swake_up(kvm_arch_vcpu_wq(vcpu)); > > > > > + } > > > > > } > > > > > > > > > > static void vcpu_sleep(struct kvm_vcpu *vcpu) > > > > > diff --git a/virt/kvm/arm/vgic/vgic-mmio.c b/virt/kvm/arm/vgic/vgic-mmio.c > > > > > index 64cbcb4..c1e4bdd 100644 > > > > > --- a/virt/kvm/arm/vgic/vgic-mmio.c > > > > > +++ b/virt/kvm/arm/vgic/vgic-mmio.c > > > > > @@ -231,23 +231,21 @@ static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq, > > > > > * be migrated while we don't hold the IRQ locks and we don't want to be > > > > > * chasing moving targets. > > > > > * > > > > > - * For private interrupts, we only have to make sure the single and only VCPU > > > > > - * that can potentially queue the IRQ is stopped. > > > > > + * For private interrupts we don't have to do anything because userspace > > > > > + * accesses to the VGIC state already require all VCPUs to be stopped, and > > > > > + * only the VCPU itself can modify its private interrupts active state, which > > > > > + * guarantees that the VCPU is not running. > > > > > */ > > > > > static void vgic_change_active_prepare(struct kvm_vcpu *vcpu, u32 intid) > > > > > { > > > > > - if (intid < VGIC_NR_PRIVATE_IRQS) > > > > > - kvm_arm_halt_vcpu(vcpu); > > > > > - else > > > > > + if (intid > VGIC_NR_PRIVATE_IRQS) > > > > > kvm_arm_halt_guest(vcpu->kvm); > > > > > } > > > > > > > > > > /* See vgic_change_active_prepare */ > > > > > static void vgic_change_active_finish(struct kvm_vcpu *vcpu, u32 intid) > > > > > { > > > > > - if (intid < VGIC_NR_PRIVATE_IRQS) > > > > > - kvm_arm_resume_vcpu(vcpu); > > > > > - else > > > > > + if (intid > VGIC_NR_PRIVATE_IRQS) > > > > > kvm_arm_resume_guest(vcpu->kvm); > > > > > } > > > > > > > > > > @@ -271,11 +269,13 @@ void vgic_mmio_write_cactive(struct kvm_vcpu *vcpu, > > > > > { > > > > > u32 intid = VGIC_ADDR_TO_INTID(addr, 1); > > > > > > > > > > + mutex_lock(&vcpu->kvm->lock); > > > > > vgic_change_active_prepare(vcpu, intid); > > > > > > > > > > __vgic_mmio_write_cactive(vcpu, addr, len, val); > > > > > > > > > > vgic_change_active_finish(vcpu, intid); > > > > > + mutex_unlock(&vcpu->kvm->lock); > > > > > > > > Any reason not to move the lock/unlock calls to prepare/finish? Also, do > > > > we need to take that mutex if intid is a PPI? > > > > > > I guess we strictly don't need to take the mutex if it's a PPI, no. > > > > > > But I actually preferred this symmetry because you can easily tell we > > > don't have a bug (famous last words) by locking and unlocking the mutex > > > in the same function. > > > > > > I don't feel strongly about it though, so I can move it if you prefer > > > it. > > > > Actually we must move the locking into the prepare/finish functions, in > > order to tuck them into the VGIC_NR_PRIVATE_IRQS conditions. Otherwise, > > with gicv3, when userspace accesses ISACTIVER0/ICACTIVER0, which are > > SGI_base offsets, then the vgic_v3_sgibase_registers table is used. That > > table doesn't provide the uaccess functions, so we try to lock twice > > again. > > > > Nice find. > > How about we always use the uaccess functions or uaccesses instead? : Yeah, that's a better suggestion. u-access, i-access, we-all-access :-) drew > > diff --git a/virt/kvm/arm/vgic/vgic-mmio-v3.c b/virt/kvm/arm/vgic/vgic-mmio-v3.c > index 23c0d564..e25567a 100644 > --- a/virt/kvm/arm/vgic/vgic-mmio-v3.c > +++ b/virt/kvm/arm/vgic/vgic-mmio-v3.c > @@ -528,12 +528,14 @@ static const struct vgic_register_region vgic_v3_sgibase_registers[] = { > vgic_mmio_read_pending, vgic_mmio_write_cpending, > vgic_mmio_read_raz, vgic_mmio_write_wi, 4, > VGIC_ACCESS_32bit), > - REGISTER_DESC_WITH_LENGTH(GICR_ISACTIVER0, > - vgic_mmio_read_active, vgic_mmio_write_sactive, 4, > - VGIC_ACCESS_32bit), > - REGISTER_DESC_WITH_LENGTH(GICR_ICACTIVER0, > - vgic_mmio_read_active, vgic_mmio_write_cactive, 4, > - VGIC_ACCESS_32bit), > + REGISTER_DESC_WITH_LENGTH_UACCESS(GICR_ISACTIVER0, > + vgic_mmio_read_active, vgic_mmio_write_sactive, > + NULL, vgic_mmio_uaccess_write_sactive, > + 4, VGIC_ACCESS_32bit), > + REGISTER_DESC_WITH_LENGTH_UACCESS(GICR_ICACTIVER0, > + vgic_mmio_read_active, vgic_mmio_write_cactive, > + NULL, vgic_mmio_uaccess_write_cactive, > + 4, VGIC_ACCESS_32bit), > REGISTER_DESC_WITH_LENGTH(GICR_IPRIORITYR0, > vgic_mmio_read_priority, vgic_mmio_write_priority, 32, > VGIC_ACCESS_32bit | VGIC_ACCESS_8bit), > > Thanks, > -Christoffer
On Sun, Jun 04, 2017 at 02:41:13PM +0200, Andrew Jones wrote: > On Sun, Jun 04, 2017 at 01:57:37PM +0200, Christoffer Dall wrote: > > On Sun, Jun 04, 2017 at 10:15:57AM +0200, Andrew Jones wrote: > > > On Tue, May 23, 2017 at 10:43:29AM +0200, Christoffer Dall wrote: > > > > On Mon, May 22, 2017 at 04:30:22PM +0100, Marc Zyngier wrote: > > > > > On 16/05/17 11:04, Christoffer Dall wrote: > > > > > > We don't need to stop a specific VCPU when changing the active state, > > > > > > because private IRQs can only be modified by a running VCPU for the > > > > > > VCPU itself and it is therefore already stopped. > > > > > > > > > > > > However, it is also possible for two VCPUs to be modifying the active > > > > > > state of SPIs at the same time, which can cause the thread being stuck > > > > > > in the loop that checks other VCPU threads for a potentially very long > > > > > > time, or to modify the active state of a running VCPU. Fix this by > > > > > > serializing all accesses to setting and clearing the active state of > > > > > > interrupts using the KVM mutex. > > > > > > > > > > > > Reported-by: Andrew Jones <drjones@redhat.com> > > > > > > Signed-off-by: Christoffer Dall <cdall@linaro.org> > > > > > > --- > > > > > > arch/arm/include/asm/kvm_host.h | 2 -- > > > > > > arch/arm64/include/asm/kvm_host.h | 2 -- > > > > > > virt/kvm/arm/arm.c | 20 ++++---------------- > > > > > > virt/kvm/arm/vgic/vgic-mmio.c | 18 ++++++++++-------- > > > > > > virt/kvm/arm/vgic/vgic.c | 11 ++++++----- > > > > > > 5 files changed, 20 insertions(+), 33 deletions(-) > > > > > > > > > > > > diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h > > > > > > index f0e6657..12274d4 100644 > > > > > > --- a/arch/arm/include/asm/kvm_host.h > > > > > > +++ b/arch/arm/include/asm/kvm_host.h > > > > > > @@ -233,8 +233,6 @@ struct kvm_vcpu *kvm_arm_get_running_vcpu(void); > > > > > > struct kvm_vcpu __percpu **kvm_get_running_vcpus(void); > > > > > > void kvm_arm_halt_guest(struct kvm *kvm); > > > > > > void kvm_arm_resume_guest(struct kvm *kvm); > > > > > > -void kvm_arm_halt_vcpu(struct kvm_vcpu *vcpu); > > > > > > -void kvm_arm_resume_vcpu(struct kvm_vcpu *vcpu); > > > > > > > > > > > > int kvm_arm_copy_coproc_indices(struct kvm_vcpu *vcpu, u64 __user *uindices); > > > > > > unsigned long kvm_arm_num_coproc_regs(struct kvm_vcpu *vcpu); > > > > > > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h > > > > > > index 5e19165..32cbe8a 100644 > > > > > > --- a/arch/arm64/include/asm/kvm_host.h > > > > > > +++ b/arch/arm64/include/asm/kvm_host.h > > > > > > @@ -333,8 +333,6 @@ struct kvm_vcpu *kvm_arm_get_running_vcpu(void); > > > > > > struct kvm_vcpu * __percpu *kvm_get_running_vcpus(void); > > > > > > void kvm_arm_halt_guest(struct kvm *kvm); > > > > > > void kvm_arm_resume_guest(struct kvm *kvm); > > > > > > -void kvm_arm_halt_vcpu(struct kvm_vcpu *vcpu); > > > > > > -void kvm_arm_resume_vcpu(struct kvm_vcpu *vcpu); > > > > > > > > > > > > u64 __kvm_call_hyp(void *hypfn, ...); > > > > > > #define kvm_call_hyp(f, ...) __kvm_call_hyp(kvm_ksym_ref(f), ##__VA_ARGS__) > > > > > > diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c > > > > > > index 3417e18..3c387fd 100644 > > > > > > --- a/virt/kvm/arm/arm.c > > > > > > +++ b/virt/kvm/arm/arm.c > > > > > > @@ -539,27 +539,15 @@ void kvm_arm_halt_guest(struct kvm *kvm) > > > > > > kvm_make_all_cpus_request(kvm, KVM_REQ_VCPU_EXIT); > > > > > > } > > > > > > > > > > > > -void kvm_arm_halt_vcpu(struct kvm_vcpu *vcpu) > > > > > > -{ > > > > > > - vcpu->arch.pause = true; > > > > > > - kvm_vcpu_kick(vcpu); > > > > > > -} > > > > > > - > > > > > > -void kvm_arm_resume_vcpu(struct kvm_vcpu *vcpu) > > > > > > -{ > > > > > > - struct swait_queue_head *wq = kvm_arch_vcpu_wq(vcpu); > > > > > > - > > > > > > - vcpu->arch.pause = false; > > > > > > - swake_up(wq); > > > > > > -} > > > > > > - > > > > > > void kvm_arm_resume_guest(struct kvm *kvm) > > > > > > { > > > > > > int i; > > > > > > struct kvm_vcpu *vcpu; > > > > > > > > > > > > - kvm_for_each_vcpu(i, vcpu, kvm) > > > > > > - kvm_arm_resume_vcpu(vcpu); > > > > > > + kvm_for_each_vcpu(i, vcpu, kvm) { > > > > > > + vcpu->arch.pause = false; > > > > > > + swake_up(kvm_arch_vcpu_wq(vcpu)); > > > > > > + } > > > > > > } > > > > > > > > > > > > static void vcpu_sleep(struct kvm_vcpu *vcpu) > > > > > > diff --git a/virt/kvm/arm/vgic/vgic-mmio.c b/virt/kvm/arm/vgic/vgic-mmio.c > > > > > > index 64cbcb4..c1e4bdd 100644 > > > > > > --- a/virt/kvm/arm/vgic/vgic-mmio.c > > > > > > +++ b/virt/kvm/arm/vgic/vgic-mmio.c > > > > > > @@ -231,23 +231,21 @@ static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq, > > > > > > * be migrated while we don't hold the IRQ locks and we don't want to be > > > > > > * chasing moving targets. > > > > > > * > > > > > > - * For private interrupts, we only have to make sure the single and only VCPU > > > > > > - * that can potentially queue the IRQ is stopped. > > > > > > + * For private interrupts we don't have to do anything because userspace > > > > > > + * accesses to the VGIC state already require all VCPUs to be stopped, and > > > > > > + * only the VCPU itself can modify its private interrupts active state, which > > > > > > + * guarantees that the VCPU is not running. > > > > > > */ > > > > > > static void vgic_change_active_prepare(struct kvm_vcpu *vcpu, u32 intid) > > > > > > { > > > > > > - if (intid < VGIC_NR_PRIVATE_IRQS) > > > > > > - kvm_arm_halt_vcpu(vcpu); > > > > > > - else > > > > > > + if (intid > VGIC_NR_PRIVATE_IRQS) > > > > > > kvm_arm_halt_guest(vcpu->kvm); > > > > > > } > > > > > > > > > > > > /* See vgic_change_active_prepare */ > > > > > > static void vgic_change_active_finish(struct kvm_vcpu *vcpu, u32 intid) > > > > > > { > > > > > > - if (intid < VGIC_NR_PRIVATE_IRQS) > > > > > > - kvm_arm_resume_vcpu(vcpu); > > > > > > - else > > > > > > + if (intid > VGIC_NR_PRIVATE_IRQS) > > > > > > kvm_arm_resume_guest(vcpu->kvm); > > > > > > } > > > > > > > > > > > > @@ -271,11 +269,13 @@ void vgic_mmio_write_cactive(struct kvm_vcpu *vcpu, > > > > > > { > > > > > > u32 intid = VGIC_ADDR_TO_INTID(addr, 1); > > > > > > > > > > > > + mutex_lock(&vcpu->kvm->lock); > > > > > > vgic_change_active_prepare(vcpu, intid); > > > > > > > > > > > > __vgic_mmio_write_cactive(vcpu, addr, len, val); > > > > > > > > > > > > vgic_change_active_finish(vcpu, intid); > > > > > > + mutex_unlock(&vcpu->kvm->lock); > > > > > > > > > > Any reason not to move the lock/unlock calls to prepare/finish? Also, do > > > > > we need to take that mutex if intid is a PPI? > > > > > > > > I guess we strictly don't need to take the mutex if it's a PPI, no. > > > > > > > > But I actually preferred this symmetry because you can easily tell we > > > > don't have a bug (famous last words) by locking and unlocking the mutex > > > > in the same function. > > > > > > > > I don't feel strongly about it though, so I can move it if you prefer > > > > it. > > > > > > Actually we must move the locking into the prepare/finish functions, in > > > order to tuck them into the VGIC_NR_PRIVATE_IRQS conditions. Otherwise, > > > with gicv3, when userspace accesses ISACTIVER0/ICACTIVER0, which are > > > SGI_base offsets, then the vgic_v3_sgibase_registers table is used. That > > > table doesn't provide the uaccess functions, so we try to lock twice > > > again. > > > > > > > Nice find. > > > > How about we always use the uaccess functions or uaccesses instead? : > > Yeah, that's a better suggestion. u-access, i-access, we-all-access :-) > cool. I've put it in kvmarm/queue. Thanks, -Christoffer
diff --git a/virt/kvm/arm/vgic/vgic-mmio-v3.c b/virt/kvm/arm/vgic/vgic-mmio-v3.c index 23c0d564..e25567a 100644 --- a/virt/kvm/arm/vgic/vgic-mmio-v3.c +++ b/virt/kvm/arm/vgic/vgic-mmio-v3.c @@ -528,12 +528,14 @@ static const struct vgic_register_region vgic_v3_sgibase_registers[] = { vgic_mmio_read_pending, vgic_mmio_write_cpending, vgic_mmio_read_raz, vgic_mmio_write_wi, 4, VGIC_ACCESS_32bit), - REGISTER_DESC_WITH_LENGTH(GICR_ISACTIVER0, - vgic_mmio_read_active, vgic_mmio_write_sactive, 4, - VGIC_ACCESS_32bit), - REGISTER_DESC_WITH_LENGTH(GICR_ICACTIVER0, - vgic_mmio_read_active, vgic_mmio_write_cactive, 4, - VGIC_ACCESS_32bit), + REGISTER_DESC_WITH_LENGTH_UACCESS(GICR_ISACTIVER0, + vgic_mmio_read_active, vgic_mmio_write_sactive, + NULL, vgic_mmio_uaccess_write_sactive, + 4, VGIC_ACCESS_32bit), + REGISTER_DESC_WITH_LENGTH_UACCESS(GICR_ICACTIVER0, + vgic_mmio_read_active, vgic_mmio_write_cactive, + NULL, vgic_mmio_uaccess_write_cactive, + 4, VGIC_ACCESS_32bit), REGISTER_DESC_WITH_LENGTH(GICR_IPRIORITYR0, vgic_mmio_read_priority, vgic_mmio_write_priority, 32, VGIC_ACCESS_32bit | VGIC_ACCESS_8bit),