lkml.org 
[lkml]   [2019]   [Apr]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v8 8/9] KVM: arm64: Add capability to advertise ptrauth for guest
From
Date
Hi,

On 4/5/19 4:33 PM, Dave Martin wrote:
> On Tue, Apr 02, 2019 at 07:57:16AM +0530, Amit Daniel Kachhap wrote:
>> This patch advertises the capability of two cpu feature called address
>> pointer authentication and generic pointer authentication. These
>> capabilities depend upon system support for pointer authentication and
>> VHE mode.
>>
>> The current arm64 KVM partially implements pointer authentication and
>> support of address/generic authentication are tied together. However,
>> separate ABI requirements for both of them is added so that the future
>> isolated implementation will not require any ABI changes.
>>
>> Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
>> Cc: Mark Rutland <mark.rutland@arm.com>
>> Cc: Marc Zyngier <marc.zyngier@arm.com>
>> Cc: Christoffer Dall <christoffer.dall@arm.com>
>> Cc: kvmarm@lists.cs.columbia.edu
>> ---
>>
>> Changes since v7:
>> * Created 2 capabilities KVM_CAP_ARM_PTRAUTH_ADDRESS and KVM_CAP_ARM_PTRAUTH_GENERIC
>> instead of one KVM_CAP_ARM_PTRAUTH [Kristina Martsenko].
>> * Added documentation here itself instead of in a new patch.
>>
>> Documentation/virtual/kvm/api.txt | 3 +++
>> arch/arm64/kvm/reset.c | 6 ++++++
>> include/uapi/linux/kvm.h | 2 ++
>> 3 files changed, 11 insertions(+)
>>
>> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
>> index aaa048d..9b56892 100644
>> --- a/Documentation/virtual/kvm/api.txt
>> +++ b/Documentation/virtual/kvm/api.txt
>> @@ -2661,8 +2661,11 @@ Possible features:
>> Depends on KVM_CAP_ARM_PMU_V3.
>> - KVM_ARM_VCPU_PTRAUTH_ADDRESS: Enables Address Pointer authentication
>> for the CPU and supported only on arm64 architecture.
>> + Depends on KVM_CAP_ARM_PTRAUTH_ADDRESS.
>> - KVM_ARM_VCPU_PTRAUTH_GENERIC: Enables Generic Pointer authentication
>> for the CPU and supported only on arm64 architecture.
>> + Depends on KVM_CAP_ARM_PTRAUTH_GENERIC.
>>
>>
>> 4.83 KVM_ARM_PREFERRED_TARGET
>> diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
>> index 717afed..8aa8982 100644
>> --- a/arch/arm64/kvm/reset.c
>> +++ b/arch/arm64/kvm/reset.c
>> @@ -92,6 +92,12 @@ int kvm_arch_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>> case KVM_CAP_ARM_VM_IPA_SIZE:
>> r = kvm_ipa_limit;
>> break;
>> + case KVM_CAP_ARM_PTRAUTH_ADDRESS:
>> + r = has_vhe() && system_supports_address_auth();
>> + break;
>> + case KVM_CAP_ARM_PTRAUTH_GENERIC:
>> + r = has_vhe() && system_supports_generic_auth();
>> + break;
>
> If some hardware supports just one auth type, we would report just one
> of these caps. Although we have the rule that userspace is not allowed
> to request these independently in KVM_ARM_VCPU_INIT anyway, I think it
> would be easier for userspace if we suppress both caps if either auth
> type isn't available on the host. e.g.:
>
> case KVM_ARM_ARM_PTRAUTH_ADDRESS:
> case KVM_ARM_ARM_PTRAUTH_GENERIC:
> r = has_vhe() && system_supports_address_auth() &&
> system_supports_generic_auth();
>
> We could revert back to the above code later on, and apply the ABI
> relaxations described in my response to the vcpu features patch, if
> someday we add support to KVM for coping with host hardware that
> supports just one auth type.
These 2 different capabilities are introduced in this iteration so I was
not clear whether to expose the suppression in capability ioctl level or
KVM_ARM_VCPU_INIT ioctl level. But agree that this way will be more
clearer to userspace.
>
>
> I'd like Mark to comment on this, since he's more aware of the
> architectural situation than I am.
ok.

Thanks,
Amit D.
>
> Cheers
> ---Dave
>

\
 
 \ /
  Last update: 2019-04-08 10:52    [W:0.075 / U:39.352 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site