* [PATCH v3 1/2] KVM: arm64: Reject VM creation when the default IPA size is unsupported [not found] <20210311100016.3830038-1-maz@kernel.org> @ 2021-03-11 10:00 ` Marc Zyngier 2021-03-11 11:08 ` Andrew Jones 2021-03-11 14:05 ` Auger Eric 2021-03-11 10:00 ` [PATCH v3 2/2] KVM: arm64: Fix exclusive limit for IPA size Marc Zyngier 1 sibling, 2 replies; 6+ messages in thread From: Marc Zyngier @ 2021-03-11 10:00 UTC (permalink / raw) To: linux-arm-kernel, kvmarm, kvm Cc: James Morse, Julien Thierry, Suzuki K Poulose, Will Deacon, Andrew Jones, Eric Auger, Alexandru Elisei, kernel-team, stable KVM/arm64 has forever used a 40bit default IPA space, partially due to its 32bit heritage (where the only choice is 40bit). However, there are implementations in the wild that have a *cough* much smaller *cough* IPA space, which leads to a misprogramming of VTCR_EL2, and a guest that is stuck on its first memory access if userspace dares to ask for the default IPA setting (which most VMMs do). Instead, blundly reject the creation of such VM, as we can't satisfy the requirements from userspace (with a one-off warning). Also clarify the boot warning, and document that the VM creation will fail when an unsupported IPA size is probided. Although this is an ABI change, it doesn't really change much for userspace: - the guest couldn't run before this change, but no error was returned. At least userspace knows what is happening. - a memory slot that was accepted because it did fit the default IPA space now doesn't even get a chance to be registered. The other thing that is left doing is to convince userspace to actually use the IPA space setting instead of relying on the antiquated default. Fixes: 233a7cb23531 ("kvm: arm64: Allow tuning the physical address size for VM") Signed-off-by: Marc Zyngier <maz@kernel.org> Cc: stable@vger.kernel.org --- Documentation/virt/kvm/api.rst | 3 +++ arch/arm64/kvm/reset.c | 12 ++++++++---- 2 files changed, 11 insertions(+), 4 deletions(-) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 1a2b5210cdbf..38e327d4b479 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -182,6 +182,9 @@ is dependent on the CPU capability and the kernel configuration. The limit can be retrieved using KVM_CAP_ARM_VM_IPA_SIZE of the KVM_CHECK_EXTENSION ioctl() at run-time. +Creation of the VM will fail if the requested IPA size (whether it is +implicit or explicit) is unsupported on the host. + Please note that configuring the IPA size does not affect the capability exposed by the guest CPUs in ID_AA64MMFR0_EL1[PARange]. It only affects size of the address translated by the stage2 level (guest physical to diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c index 47f3f035f3ea..9d3d09a89894 100644 --- a/arch/arm64/kvm/reset.c +++ b/arch/arm64/kvm/reset.c @@ -324,10 +324,9 @@ int kvm_set_ipa_limit(void) } kvm_ipa_limit = id_aa64mmfr0_parange_to_phys_shift(parange); - WARN(kvm_ipa_limit < KVM_PHYS_SHIFT, - "KVM IPA Size Limit (%d bits) is smaller than default size\n", - kvm_ipa_limit); - kvm_info("IPA Size Limit: %d bits\n", kvm_ipa_limit); + kvm_info("IPA Size Limit: %d bits%s\n", kvm_ipa_limit, + ((kvm_ipa_limit < KVM_PHYS_SHIFT) ? + " (Reduced IPA size, limited VM/VMM compatibility)" : "")); return 0; } @@ -356,6 +355,11 @@ int kvm_arm_setup_stage2(struct kvm *kvm, unsigned long type) return -EINVAL; } else { phys_shift = KVM_PHYS_SHIFT; + if (phys_shift > kvm_ipa_limit) { + pr_warn_once("%s using unsupported default IPA limit, upgrade your VMM\n", + current->comm); + return -EINVAL; + } } mmfr0 = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1); -- 2.29.2 ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH v3 1/2] KVM: arm64: Reject VM creation when the default IPA size is unsupported 2021-03-11 10:00 ` [PATCH v3 1/2] KVM: arm64: Reject VM creation when the default IPA size is unsupported Marc Zyngier @ 2021-03-11 11:08 ` Andrew Jones 2021-03-11 14:05 ` Auger Eric 1 sibling, 0 replies; 6+ messages in thread From: Andrew Jones @ 2021-03-11 11:08 UTC (permalink / raw) To: Marc Zyngier Cc: linux-arm-kernel, kvmarm, kvm, James Morse, Julien Thierry, Suzuki K Poulose, Will Deacon, Eric Auger, Alexandru Elisei, kernel-team, stable On Thu, Mar 11, 2021 at 10:00:15AM +0000, Marc Zyngier wrote: > KVM/arm64 has forever used a 40bit default IPA space, partially > due to its 32bit heritage (where the only choice is 40bit). > > However, there are implementations in the wild that have a *cough* > much smaller *cough* IPA space, which leads to a misprogramming of > VTCR_EL2, and a guest that is stuck on its first memory access > if userspace dares to ask for the default IPA setting (which most > VMMs do). > > Instead, blundly reject the creation of such VM, as we can't > satisfy the requirements from userspace (with a one-off warning). > Also clarify the boot warning, and document that the VM creation > will fail when an unsupported IPA size is probided. provided > > Although this is an ABI change, it doesn't really change much > for userspace: > > - the guest couldn't run before this change, but no error was > returned. At least userspace knows what is happening. > > - a memory slot that was accepted because it did fit the default > IPA space now doesn't even get a chance to be registered. > > The other thing that is left doing is to convince userspace to > actually use the IPA space setting instead of relying on the > antiquated default. > > Fixes: 233a7cb23531 ("kvm: arm64: Allow tuning the physical address size for VM") > Signed-off-by: Marc Zyngier <maz@kernel.org> > Cc: stable@vger.kernel.org > --- > Documentation/virt/kvm/api.rst | 3 +++ > arch/arm64/kvm/reset.c | 12 ++++++++---- > 2 files changed, 11 insertions(+), 4 deletions(-) > > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst > index 1a2b5210cdbf..38e327d4b479 100644 > --- a/Documentation/virt/kvm/api.rst > +++ b/Documentation/virt/kvm/api.rst > @@ -182,6 +182,9 @@ is dependent on the CPU capability and the kernel configuration. The limit can > be retrieved using KVM_CAP_ARM_VM_IPA_SIZE of the KVM_CHECK_EXTENSION > ioctl() at run-time. > > +Creation of the VM will fail if the requested IPA size (whether it is > +implicit or explicit) is unsupported on the host. > + > Please note that configuring the IPA size does not affect the capability > exposed by the guest CPUs in ID_AA64MMFR0_EL1[PARange]. It only affects > size of the address translated by the stage2 level (guest physical to > diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c > index 47f3f035f3ea..9d3d09a89894 100644 > --- a/arch/arm64/kvm/reset.c > +++ b/arch/arm64/kvm/reset.c > @@ -324,10 +324,9 @@ int kvm_set_ipa_limit(void) > } > > kvm_ipa_limit = id_aa64mmfr0_parange_to_phys_shift(parange); > - WARN(kvm_ipa_limit < KVM_PHYS_SHIFT, > - "KVM IPA Size Limit (%d bits) is smaller than default size\n", > - kvm_ipa_limit); > - kvm_info("IPA Size Limit: %d bits\n", kvm_ipa_limit); > + kvm_info("IPA Size Limit: %d bits%s\n", kvm_ipa_limit, > + ((kvm_ipa_limit < KVM_PHYS_SHIFT) ? > + " (Reduced IPA size, limited VM/VMM compatibility)" : "")); nit: there's a couple pair of unnecessary () > > return 0; > } > @@ -356,6 +355,11 @@ int kvm_arm_setup_stage2(struct kvm *kvm, unsigned long type) > return -EINVAL; > } else { > phys_shift = KVM_PHYS_SHIFT; > + if (phys_shift > kvm_ipa_limit) { > + pr_warn_once("%s using unsupported default IPA limit, upgrade your VMM\n", > + current->comm); > + return -EINVAL; > + } > } > > mmfr0 = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1); > -- > 2.29.2 > Reviewed-by: Andrew Jones <drjones@redhat.com> Thanks, drew ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v3 1/2] KVM: arm64: Reject VM creation when the default IPA size is unsupported 2021-03-11 10:00 ` [PATCH v3 1/2] KVM: arm64: Reject VM creation when the default IPA size is unsupported Marc Zyngier 2021-03-11 11:08 ` Andrew Jones @ 2021-03-11 14:05 ` Auger Eric 1 sibling, 0 replies; 6+ messages in thread From: Auger Eric @ 2021-03-11 14:05 UTC (permalink / raw) To: Marc Zyngier, linux-arm-kernel, kvmarm, kvm Cc: James Morse, Julien Thierry, Suzuki K Poulose, Will Deacon, Andrew Jones, Alexandru Elisei, kernel-team, stable Hi Marc, On 3/11/21 11:00 AM, Marc Zyngier wrote: > KVM/arm64 has forever used a 40bit default IPA space, partially > due to its 32bit heritage (where the only choice is 40bit). > > However, there are implementations in the wild that have a *cough* > much smaller *cough* IPA space, which leads to a misprogramming of > VTCR_EL2, and a guest that is stuck on its first memory access > if userspace dares to ask for the default IPA setting (which most > VMMs do). > > Instead, blundly reject the creation of such VM, as we can't > satisfy the requirements from userspace (with a one-off warning). > Also clarify the boot warning, and document that the VM creation > will fail when an unsupported IPA size is probided. > > Although this is an ABI change, it doesn't really change much > for userspace: > > - the guest couldn't run before this change, but no error was > returned. At least userspace knows what is happening. > > - a memory slot that was accepted because it did fit the default > IPA space now doesn't even get a chance to be registered. > > The other thing that is left doing is to convince userspace to > actually use the IPA space setting instead of relying on the > antiquated default. > > Fixes: 233a7cb23531 ("kvm: arm64: Allow tuning the physical address size for VM") > Signed-off-by: Marc Zyngier <maz@kernel.org> > Cc: stable@vger.kernel.org Reviewed-by: Eric Auger <eric.auger@redhat.com> Thanks Eric > --- > Documentation/virt/kvm/api.rst | 3 +++ > arch/arm64/kvm/reset.c | 12 ++++++++---- > 2 files changed, 11 insertions(+), 4 deletions(-) > > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst > index 1a2b5210cdbf..38e327d4b479 100644 > --- a/Documentation/virt/kvm/api.rst > +++ b/Documentation/virt/kvm/api.rst > @@ -182,6 +182,9 @@ is dependent on the CPU capability and the kernel configuration. The limit can > be retrieved using KVM_CAP_ARM_VM_IPA_SIZE of the KVM_CHECK_EXTENSION > ioctl() at run-time. > > +Creation of the VM will fail if the requested IPA size (whether it is > +implicit or explicit) is unsupported on the host. > + > Please note that configuring the IPA size does not affect the capability > exposed by the guest CPUs in ID_AA64MMFR0_EL1[PARange]. It only affects > size of the address translated by the stage2 level (guest physical to > diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c > index 47f3f035f3ea..9d3d09a89894 100644 > --- a/arch/arm64/kvm/reset.c > +++ b/arch/arm64/kvm/reset.c > @@ -324,10 +324,9 @@ int kvm_set_ipa_limit(void) > } > > kvm_ipa_limit = id_aa64mmfr0_parange_to_phys_shift(parange); > - WARN(kvm_ipa_limit < KVM_PHYS_SHIFT, > - "KVM IPA Size Limit (%d bits) is smaller than default size\n", > - kvm_ipa_limit); > - kvm_info("IPA Size Limit: %d bits\n", kvm_ipa_limit); > + kvm_info("IPA Size Limit: %d bits%s\n", kvm_ipa_limit, > + ((kvm_ipa_limit < KVM_PHYS_SHIFT) ? > + " (Reduced IPA size, limited VM/VMM compatibility)" : "")); > > return 0; > } > @@ -356,6 +355,11 @@ int kvm_arm_setup_stage2(struct kvm *kvm, unsigned long type) > return -EINVAL; > } else { > phys_shift = KVM_PHYS_SHIFT; > + if (phys_shift > kvm_ipa_limit) { > + pr_warn_once("%s using unsupported default IPA limit, upgrade your VMM\n", > + current->comm); > + return -EINVAL; > + } > } > > mmfr0 = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1); > ^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH v3 2/2] KVM: arm64: Fix exclusive limit for IPA size [not found] <20210311100016.3830038-1-maz@kernel.org> 2021-03-11 10:00 ` [PATCH v3 1/2] KVM: arm64: Reject VM creation when the default IPA size is unsupported Marc Zyngier @ 2021-03-11 10:00 ` Marc Zyngier 2021-03-11 11:15 ` Andrew Jones 1 sibling, 1 reply; 6+ messages in thread From: Marc Zyngier @ 2021-03-11 10:00 UTC (permalink / raw) To: linux-arm-kernel, kvmarm, kvm Cc: James Morse, Julien Thierry, Suzuki K Poulose, Will Deacon, Andrew Jones, Eric Auger, Alexandru Elisei, kernel-team, stable When registering a memslot, we check the size and location of that memslot against the IPA size to ensure that we can provide guest access to the whole of the memory. Unfortunately, this check rejects memslot that end-up at the exact limit of the addressing capability for a given IPA size. For example, it refuses the creation of a 2GB memslot at 0x8000000 with a 32bit IPA space. Fix it by relaxing the check to accept a memslot reaching the limit of the IPA space. Fixes: e55cac5bf2a9 ("kvm: arm/arm64: Prepare for VM specific stage2 translations") Reviewed-by: Eric Auger <eric.auger@redhat.com> Signed-off-by: Marc Zyngier <maz@kernel.org> Cc: stable@vger.kernel.org --- arch/arm64/kvm/mmu.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index 77cb2d28f2a4..8711894db8c2 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -1312,8 +1312,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm, * Prevent userspace from creating a memory region outside of the IPA * space addressable by the KVM guest IPA space. */ - if (memslot->base_gfn + memslot->npages >= - (kvm_phys_size(kvm) >> PAGE_SHIFT)) + if ((memslot->base_gfn + memslot->npages) > (kvm_phys_size(kvm) >> PAGE_SHIFT)) return -EFAULT; mmap_read_lock(current->mm); -- 2.29.2 ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH v3 2/2] KVM: arm64: Fix exclusive limit for IPA size 2021-03-11 10:00 ` [PATCH v3 2/2] KVM: arm64: Fix exclusive limit for IPA size Marc Zyngier @ 2021-03-11 11:15 ` Andrew Jones 2021-03-12 15:44 ` Marc Zyngier 0 siblings, 1 reply; 6+ messages in thread From: Andrew Jones @ 2021-03-11 11:15 UTC (permalink / raw) To: Marc Zyngier Cc: linux-arm-kernel, kvmarm, kvm, James Morse, Julien Thierry, Suzuki K Poulose, Will Deacon, Eric Auger, Alexandru Elisei, kernel-team, stable On Thu, Mar 11, 2021 at 10:00:16AM +0000, Marc Zyngier wrote: > When registering a memslot, we check the size and location of that > memslot against the IPA size to ensure that we can provide guest > access to the whole of the memory. > > Unfortunately, this check rejects memslot that end-up at the exact > limit of the addressing capability for a given IPA size. For example, > it refuses the creation of a 2GB memslot at 0x8000000 with a 32bit > IPA space. > > Fix it by relaxing the check to accept a memslot reaching the > limit of the IPA space. > > Fixes: e55cac5bf2a9 ("kvm: arm/arm64: Prepare for VM specific stage2 translations") Isn't this actually fixing commit c3058d5da222 ("arm/arm64: KVM: Ensure memslots are within KVM_PHYS_SIZE") ? > Reviewed-by: Eric Auger <eric.auger@redhat.com> > Signed-off-by: Marc Zyngier <maz@kernel.org> > Cc: stable@vger.kernel.org > --- > arch/arm64/kvm/mmu.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c > index 77cb2d28f2a4..8711894db8c2 100644 > --- a/arch/arm64/kvm/mmu.c > +++ b/arch/arm64/kvm/mmu.c > @@ -1312,8 +1312,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm, > * Prevent userspace from creating a memory region outside of the IPA > * space addressable by the KVM guest IPA space. > */ > - if (memslot->base_gfn + memslot->npages >= > - (kvm_phys_size(kvm) >> PAGE_SHIFT)) > + if ((memslot->base_gfn + memslot->npages) > (kvm_phys_size(kvm) >> PAGE_SHIFT)) > return -EFAULT; > > mmap_read_lock(current->mm); > -- > 2.29.2 > Otherwise Reviewed-by: Andrew Jones <drjones@redhat.com> Thanks, drew ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v3 2/2] KVM: arm64: Fix exclusive limit for IPA size 2021-03-11 11:15 ` Andrew Jones @ 2021-03-12 15:44 ` Marc Zyngier 0 siblings, 0 replies; 6+ messages in thread From: Marc Zyngier @ 2021-03-12 15:44 UTC (permalink / raw) To: Andrew Jones Cc: linux-arm-kernel, kvmarm, kvm, James Morse, Julien Thierry, Suzuki K Poulose, Will Deacon, Eric Auger, Alexandru Elisei, kernel-team, stable On 2021-03-11 11:15, Andrew Jones wrote: > On Thu, Mar 11, 2021 at 10:00:16AM +0000, Marc Zyngier wrote: >> When registering a memslot, we check the size and location of that >> memslot against the IPA size to ensure that we can provide guest >> access to the whole of the memory. >> >> Unfortunately, this check rejects memslot that end-up at the exact >> limit of the addressing capability for a given IPA size. For example, >> it refuses the creation of a 2GB memslot at 0x8000000 with a 32bit >> IPA space. >> >> Fix it by relaxing the check to accept a memslot reaching the >> limit of the IPA space. >> >> Fixes: e55cac5bf2a9 ("kvm: arm/arm64: Prepare for VM specific stage2 >> translations") > > Isn't this actually fixing commit c3058d5da222 ("arm/arm64: KVM: Ensure > memslots are within KVM_PHYS_SIZE") ? Ah, yes, that's indeed better (more backport work... ;-) Thanks, M. -- Jazz is not dead. It just smells funny... ^ permalink raw reply [flat|nested] 6+ messages in thread
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2021-03-11 10:00 ` [PATCH v3 1/2] KVM: arm64: Reject VM creation when the default IPA size is unsupported Marc Zyngier
2021-03-11 11:08 ` Andrew Jones
2021-03-11 14:05 ` Auger Eric
2021-03-11 10:00 ` [PATCH v3 2/2] KVM: arm64: Fix exclusive limit for IPA size Marc Zyngier
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