linux-kernel - Re: [PATCH v7 7/10] KVM: arm/arm64: context-switch ptrauth registers

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Date:   Wed, 27 Mar 2019 08:51:09 +0530
From:   Amit Daniel Kachhap <amit.kachhap@....com>
To:     Kristina Martsenko <kristina.martsenko@....com>,
        linux-arm-kernel@...ts.infradead.org
Cc:     Christoffer Dall <christoffer.dall@....com>,
        Marc Zyngier <marc.zyngier@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Andrew Jones <drjones@...hat.com>,
        Dave Martin <Dave.Martin@....com>,
        Ramana Radhakrishnan <ramana.radhakrishnan@....com>,
        kvmarm@...ts.cs.columbia.edu, linux-kernel@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry@....com>
Subject: Re: [PATCH v7 7/10] KVM: arm/arm64: context-switch ptrauth registers



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@....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
>