* [PATCH v3 1/2] KVM: arm64: Reject VM creation when the default IPA size is unsupported
@ 2021-03-11 10:00 ` Marc Zyngier
0 siblings, 0 replies; 24+ 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
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply related [flat|nested] 24+ messages in thread
* [PATCH v3 1/2] KVM: arm64: Reject VM creation when the default IPA size is unsupported
@ 2021-03-11 10:00 ` Marc Zyngier
0 siblings, 0 replies; 24+ messages in thread
From: Marc Zyngier @ 2021-03-11 10:00 UTC (permalink / raw)
To: linux-arm-kernel, kvmarm, kvm; +Cc: kernel-team, stable, Will Deacon
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
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
^ permalink raw reply related [flat|nested] 24+ 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 ` Marc Zyngier
(?)
@ 2021-03-11 11:08 ` Andrew Jones
-1 siblings, 0 replies; 24+ 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] 24+ messages in thread
* Re: [PATCH v3 1/2] KVM: arm64: Reject VM creation when the default IPA size is unsupported
@ 2021-03-11 11:08 ` Andrew Jones
0 siblings, 0 replies; 24+ 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
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [PATCH v3 1/2] KVM: arm64: Reject VM creation when the default IPA size is unsupported
@ 2021-03-11 11:08 ` Andrew Jones
0 siblings, 0 replies; 24+ messages in thread
From: Andrew Jones @ 2021-03-11 11:08 UTC (permalink / raw)
To: Marc Zyngier
Cc: kernel-team, kvm, stable, linux-arm-kernel, Will Deacon, kvmarm
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
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
^ permalink raw reply [flat|nested] 24+ 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 ` Marc Zyngier
(?)
@ 2021-03-11 14:05 ` Auger Eric
-1 siblings, 0 replies; 24+ 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] 24+ messages in thread
* Re: [PATCH v3 1/2] KVM: arm64: Reject VM creation when the default IPA size is unsupported
@ 2021-03-11 14:05 ` Auger Eric
0 siblings, 0 replies; 24+ 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);
>
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 24+ messages in thread
* Re: [PATCH v3 1/2] KVM: arm64: Reject VM creation when the default IPA size is unsupported
@ 2021-03-11 14:05 ` Auger Eric
0 siblings, 0 replies; 24+ messages in thread
From: Auger Eric @ 2021-03-11 14:05 UTC (permalink / raw)
To: Marc Zyngier, linux-arm-kernel, kvmarm, kvm
Cc: kernel-team, Will Deacon, 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);
>
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
^ permalink raw reply [flat|nested] 24+ messages in thread