linux-kernel - Re: [PATCH v7 5/10] KVM: arm/arm64: preserve host MDCR

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Message-ID: <bce98120-b844-f4a2-cd44-a0e8418dfd13@arm.com>
Date:   Tue, 26 Mar 2019 09:25:36 +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 5/10] KVM: arm/arm64: preserve host MDCR_EL2 value

Hi,

On 3/26/19 1:34 AM, Kristina Martsenko wrote:
> On 19/03/2019 08:30, Amit Daniel Kachhap wrote:
>> Save host MDCR_EL2 value during kvm HYP initialisation and restore
>> after every switch from host to guest. There should not be any
>> change in functionality due to this.
>>
>> The value of mdcr_el2 is now stored in struct kvm_cpu_context as
>> both host and guest can now use this field in a common way.
>>
>> Signed-off-by: Amit Daniel Kachhap <amit.kachhap@....com>
>> Acked-by: Mark Rutland <mark.rutland@....com>
>> Cc: Marc Zyngier <marc.zyngier@....com>
>> Cc: Mark Rutland <mark.rutland@....com>
>> Cc: Christoffer Dall <christoffer.dall@....com>
>> Cc: kvmarm@...ts.cs.columbia.edu
> 
> [...]
> 
>>   /**
>> - * kvm_arm_init_debug - grab what we need for debug
>> - *
>> - * Currently the sole task of this function is to retrieve the initial
>> - * value of mdcr_el2 so we can preserve MDCR_EL2.HPMN which has
>> - * presumably been set-up by some knowledgeable bootcode.
>> - *
>> - * It is called once per-cpu during CPU hyp initialisation.
>> - */
>> -
>> -void kvm_arm_init_debug(void)
>> -{
>> -	__this_cpu_write(mdcr_el2, kvm_call_hyp_ret(__kvm_get_mdcr_el2));
>> -}
> 
> The __kvm_get_mdcr_el2 function is no longer used anywhere, so can also
> be removed.
Nice catch. Will do.

Thanks,
Amit D
> 
> Thanks,
> Kristina
>