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

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Date:   Tue, 26 Mar 2019 18:01:44 +0000
From:   Kristina Martsenko <kristina.martsenko@....com>
To:     Amit Daniel Kachhap <amit.kachhap@....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 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).

Thanks,
Kristina