From: Christoffer Dall <christoffer.dall@arm.com> To: kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Cc: kvm@vger.kernel.org, Marc Zyngier <marc.zyngier@arm.com>, Andre Przywara <andre.przywara@arm.com> Subject: [PATCH v4 09/10] KVM: arm/arm64: vgic: Let userspace opt-in to writable v2 IGROUPR Date: Mon, 16 Jul 2018 15:06:26 +0200 [thread overview] Message-ID: <1531746387-7033-10-git-send-email-christoffer.dall@arm.com> (raw) In-Reply-To: <1531746387-7033-1-git-send-email-christoffer.dall@arm.com> Simply letting IGROUPR be writable from userspace would break migration from old kernels to newer kernels, because old kernels incorrectly report interrupt groups as group 1. This would not be a big problem if userspace wrote GICD_IIDR as read from the kernel, because we could detect the incompatibility and return an error to userspace. Unfortunately, this is not the case with current userspace implementations and simply letting IGROUPR be writable from userspace for an emulated GICv2 silently breaks migration and causes the destination VM to no longer run after migration. We now encourage userspace to write the read and expected value of GICD_IIDR as the first part of a GIC register restore, and if we observe a write to GICD_IIDR we know that userspace has been updated and has had a chance to cope with older kernels (VGICv2 IIDR.Revision == 0) incorrectly reporting interrupts as group 1, and therefore we now allow groups to be user writable. Signed-off-by: Christoffer Dall <christoffer.dall@arm.com> --- include/kvm/arm_vgic.h | 3 +++ virt/kvm/arm/vgic/vgic-mmio-v2.c | 16 +++++++++++++++- 2 files changed, 18 insertions(+), 1 deletion(-) diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h index c661d0e..c134790 100644 --- a/include/kvm/arm_vgic.h +++ b/include/kvm/arm_vgic.h @@ -221,6 +221,9 @@ struct vgic_dist { /* Implementation revision as reported in the GICD_IIDR */ u32 implementation_rev; + /* Userspace can write to GICv2 IGROUPR */ + bool v2_groups_user_writable; + /* Do injected MSIs require an additional device ID? */ bool msis_require_devid; diff --git a/virt/kvm/arm/vgic/vgic-mmio-v2.c b/virt/kvm/arm/vgic/vgic-mmio-v2.c index ee164f8..26654f4 100644 --- a/virt/kvm/arm/vgic/vgic-mmio-v2.c +++ b/virt/kvm/arm/vgic/vgic-mmio-v2.c @@ -85,6 +85,18 @@ static int vgic_mmio_uaccess_write_v2_misc(struct kvm_vcpu *vcpu, case GIC_DIST_IIDR: if (val != vgic_mmio_read_v2_misc(vcpu, addr, len)) return -EINVAL; + + /* + * If we observe a write to GICD_IIDR we know that userspace + * has been updated and has had a chance to cope with older + * kernels (VGICv2 IIDR.Revision == 0) incorrectly reporting + * interrupts as group 1, and therefore we now allow groups to + * be user writable. Doing this by default would break + * migration from old kernels to new kernels with legacy + * userspace. + */ + vcpu->kvm->arch.vgic.v2_groups_user_writable = true; + return 0; } vgic_mmio_write_v2_misc(vcpu, addr, len, val); @@ -95,7 +107,9 @@ static int vgic_mmio_uaccess_write_v2_group(struct kvm_vcpu *vcpu, gpa_t addr, unsigned int len, unsigned long val) { - /* Ignore writes from userspace */ + if (vcpu->kvm->arch.vgic.v2_groups_user_writable) + vgic_mmio_write_group(vcpu, addr, len, val); + return 0; } -- 2.7.4
WARNING: multiple messages have this Message-ID (diff)
From: christoffer.dall@arm.com (Christoffer Dall) To: linux-arm-kernel@lists.infradead.org Subject: [PATCH v4 09/10] KVM: arm/arm64: vgic: Let userspace opt-in to writable v2 IGROUPR Date: Mon, 16 Jul 2018 15:06:26 +0200 [thread overview] Message-ID: <1531746387-7033-10-git-send-email-christoffer.dall@arm.com> (raw) In-Reply-To: <1531746387-7033-1-git-send-email-christoffer.dall@arm.com> Simply letting IGROUPR be writable from userspace would break migration from old kernels to newer kernels, because old kernels incorrectly report interrupt groups as group 1. This would not be a big problem if userspace wrote GICD_IIDR as read from the kernel, because we could detect the incompatibility and return an error to userspace. Unfortunately, this is not the case with current userspace implementations and simply letting IGROUPR be writable from userspace for an emulated GICv2 silently breaks migration and causes the destination VM to no longer run after migration. We now encourage userspace to write the read and expected value of GICD_IIDR as the first part of a GIC register restore, and if we observe a write to GICD_IIDR we know that userspace has been updated and has had a chance to cope with older kernels (VGICv2 IIDR.Revision == 0) incorrectly reporting interrupts as group 1, and therefore we now allow groups to be user writable. Signed-off-by: Christoffer Dall <christoffer.dall@arm.com> --- include/kvm/arm_vgic.h | 3 +++ virt/kvm/arm/vgic/vgic-mmio-v2.c | 16 +++++++++++++++- 2 files changed, 18 insertions(+), 1 deletion(-) diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h index c661d0e..c134790 100644 --- a/include/kvm/arm_vgic.h +++ b/include/kvm/arm_vgic.h @@ -221,6 +221,9 @@ struct vgic_dist { /* Implementation revision as reported in the GICD_IIDR */ u32 implementation_rev; + /* Userspace can write to GICv2 IGROUPR */ + bool v2_groups_user_writable; + /* Do injected MSIs require an additional device ID? */ bool msis_require_devid; diff --git a/virt/kvm/arm/vgic/vgic-mmio-v2.c b/virt/kvm/arm/vgic/vgic-mmio-v2.c index ee164f8..26654f4 100644 --- a/virt/kvm/arm/vgic/vgic-mmio-v2.c +++ b/virt/kvm/arm/vgic/vgic-mmio-v2.c @@ -85,6 +85,18 @@ static int vgic_mmio_uaccess_write_v2_misc(struct kvm_vcpu *vcpu, case GIC_DIST_IIDR: if (val != vgic_mmio_read_v2_misc(vcpu, addr, len)) return -EINVAL; + + /* + * If we observe a write to GICD_IIDR we know that userspace + * has been updated and has had a chance to cope with older + * kernels (VGICv2 IIDR.Revision == 0) incorrectly reporting + * interrupts as group 1, and therefore we now allow groups to + * be user writable. Doing this by default would break + * migration from old kernels to new kernels with legacy + * userspace. + */ + vcpu->kvm->arch.vgic.v2_groups_user_writable = true; + return 0; } vgic_mmio_write_v2_misc(vcpu, addr, len, val); @@ -95,7 +107,9 @@ static int vgic_mmio_uaccess_write_v2_group(struct kvm_vcpu *vcpu, gpa_t addr, unsigned int len, unsigned long val) { - /* Ignore writes from userspace */ + if (vcpu->kvm->arch.vgic.v2_groups_user_writable) + vgic_mmio_write_group(vcpu, addr, len, val); + return 0; } -- 2.7.4
next prev parent reply other threads:[~2018-07-16 13:06 UTC|newest] Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-07-16 13:06 [PATCH v4 00/10] KVM: arm/arm64: vgic: Virtual interrupt grouping support Christoffer Dall 2018-07-16 13:06 ` Christoffer Dall 2018-07-16 13:06 ` [PATCH v4 01/10] KVM: arm/arm64: vgic: Define GICD_IIDR fields for GICv2 and GIv3 Christoffer Dall 2018-07-16 13:06 ` Christoffer Dall 2018-07-19 16:08 ` Andrew Jones 2018-07-19 16:08 ` Andrew Jones 2018-07-16 13:06 ` [PATCH v4 02/10] KVM: arm/arm64: vgic: Keep track of implementation revision Christoffer Dall 2018-07-16 13:06 ` Christoffer Dall 2018-07-19 16:11 ` Andrew Jones 2018-07-19 16:11 ` Andrew Jones 2018-07-16 13:06 ` [PATCH v4 03/10] KVM: arm/arm64: vgic: GICv2 IGROUPR should read as zero Christoffer Dall 2018-07-16 13:06 ` Christoffer Dall 2018-07-19 18:16 ` Andrew Jones 2018-07-19 18:16 ` Andrew Jones 2018-07-19 20:56 ` Christoffer Dall 2018-07-19 20:56 ` Christoffer Dall 2018-07-16 13:06 ` [PATCH v4 04/10] KVM: arm/arm64: vgic: Add group field to struct irq Christoffer Dall 2018-07-16 13:06 ` Christoffer Dall 2018-07-19 16:16 ` Andrew Jones 2018-07-19 16:16 ` Andrew Jones 2018-07-16 13:06 ` [PATCH v4 05/10] KVM: arm/arm64: vgic: Signal IRQs using their configured group Christoffer Dall 2018-07-16 13:06 ` Christoffer Dall 2018-07-19 16:28 ` Andrew Jones 2018-07-19 16:28 ` Andrew Jones 2018-07-16 13:06 ` [PATCH v4 06/10] KVM: arm/arm64: vgic: Permit uaccess writes to return errors Christoffer Dall 2018-07-16 13:06 ` Christoffer Dall 2018-07-19 16:31 ` Andrew Jones 2018-07-19 16:31 ` Andrew Jones 2018-07-16 13:06 ` [PATCH v4 07/10] KVM: arm/arm64: vgic: Return error on incompatible uaccess GICD_IIDR writes Christoffer Dall 2018-07-16 13:06 ` Christoffer Dall 2018-07-16 15:43 ` Bharat Bhushan 2018-07-16 15:43 ` Bharat Bhushan 2018-07-17 9:10 ` Christoffer Dall 2018-07-17 9:10 ` Christoffer Dall 2018-07-19 17:09 ` Andrew Jones 2018-07-19 17:09 ` Andrew Jones 2018-07-16 13:06 ` [PATCH v4 08/10] KVM: arm/arm64: vgic: Allow configuration of interrupt groups Christoffer Dall 2018-07-16 13:06 ` Christoffer Dall 2018-07-19 17:26 ` Andrew Jones 2018-07-19 17:26 ` Andrew Jones 2018-07-16 13:06 ` Christoffer Dall [this message] 2018-07-16 13:06 ` [PATCH v4 09/10] KVM: arm/arm64: vgic: Let userspace opt-in to writable v2 IGROUPR Christoffer Dall 2018-07-19 18:17 ` Andrew Jones 2018-07-19 18:17 ` Andrew Jones 2018-07-16 13:06 ` [PATCH v4 10/10] KVM: arm/arm64: vgic: Update documentation of the GIC devices wrt IIDR Christoffer Dall 2018-07-16 13:06 ` Christoffer Dall 2018-07-16 15:59 ` Bharat Bhushan 2018-07-16 15:59 ` Bharat Bhushan 2018-07-17 9:13 ` Christoffer Dall 2018-07-17 9:13 ` Christoffer Dall 2018-07-18 10:45 ` Bharat Bhushan 2018-07-18 10:45 ` Bharat Bhushan 2018-07-19 17:08 ` Andrew Jones 2018-07-19 17:08 ` Andrew Jones 2018-07-19 20:57 ` Christoffer Dall 2018-07-19 20:57 ` Christoffer Dall 2018-07-20 10:12 ` [PATCH v4 00/10] KVM: arm/arm64: vgic: Virtual interrupt grouping support Marc Zyngier 2018-07-20 10:12 ` Marc Zyngier
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