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Subject: Re: [PATCH v7 7/10] KVM: arm/arm64: context-switch ptrauth registers
To:     Kristina Martsenko <kristina.martsenko@arm.com>,
        linux-arm-kernel@lists.infradead.org
Cc:     Christoffer Dall <christoffer.dall@arm.com>,
        Marc Zyngier <marc.zyngier@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Andrew Jones <drjones@redhat.com>,
        Dave Martin <Dave.Martin@arm.com>,
        Ramana Radhakrishnan <ramana.radhakrishnan@arm.com>,
        kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org,
        Mark Rutland <mark.rutland@arm.com>,
        James Morse <james.morse@arm.com>,
        Julien Thierry <julien.thierry@arm.com>
References: <1552984243-7689-1-git-send-email-amit.kachhap@arm.com>
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 <64505666-8a1f-cf64-7067-4b2dd53b0b40@arm.com>
 <da7091a9-01b2-bead-3777-972fbb293def@arm.com>
 <949327ae-081c-0964-3315-ac2695243b5f@arm.com>
From:   Amit Daniel Kachhap <amit.kachhap@arm.com>
Message-ID: <536f518d-5425-cb94-3f64-4c56e5cd65c1@arm.com>
Date:   Wed, 27 Mar 2019 08:51:09 +0530
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On 3/26/19 11:31 PM, Kristina Martsenko wrote:
> On 26/03/2019 04:03, Amit Daniel Kachhap wrote:
>> Hi,
>>
>> On 3/26/19 1:34 AM, Kristina Martsenko wrote:
>>> On 19/03/2019 08:30, Amit Daniel Kachhap wrote:
>>>> From: Mark Rutland <mark.rutland@arm.com>
>>>>
>>>> When pointer authentication is supported, a guest may wish to use it.
>>>> This patch adds the necessary KVM infrastructure for this to work, with
>>>> a semi-lazy context switch of the pointer auth state.
>>>
>>> [...]
>>>
>>>> +    if (test_bit(KVM_ARM_VCPU_PTRAUTH_ADDRESS, vcpu->arch.features) ||
>>>> +        test_bit(KVM_ARM_VCPU_PTRAUTH_GENERIC, vcpu->arch.features)) {
>>>> +        /* Verify that KVM startup matches the conditions for ptrauth */
>>>> +        if (WARN_ON(!vcpu_has_ptrauth(vcpu)))
>>>> +            return -EINVAL;
>>>> +    }
>>>
>>> I think this now needs to have "goto out;" instead of "return -EINVAL;",
>>> since 5.1-rcX contains commit e761a927bc9a ("KVM: arm/arm64: Reset the
>>> VCPU without preemption and vcpu state loaded") which changed some of
>>> this code.
>> ok missed the changes for this commit.
> 
> One more thing - I think the WARN_ON() here should be removed. Otherwise
> if panic_on_warn is set then userspace can panic the kernel. I think
> WARN_ON is only for internal kernel errors (see comment in
> include/asm-generic/bug.h).

The documentation makes sense so in this case a pr_err like message 
will suffice. Btw there is one WARN in the function kvm_set_ipa_limit in 
the same file.

Thanks,
Amit D
> 
> Thanks,
> Kristina
>