linux-kernel - Re: [PATCH v3 2/6] KVM: arm64: maintain per VM value for CTR

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Date: Thu, 30 May 2024 14:17:33 +0200
From: Eric Auger <eauger@...hat.com>
To: Sebastian Ott <sebott@...hat.com>
Cc: linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
 linux-kernel@...r.kernel.org, Marc Zyngier <maz@...nel.org>,
 Oliver Upton <oliver.upton@...ux.dev>, James Morse <james.morse@....com>,
 Suzuki K Poulose <suzuki.poulose@....com>,
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>
Subject: Re: [PATCH v3 2/6] KVM: arm64: maintain per VM value for CTR_EL0



On 5/30/24 13:24, Sebastian Ott wrote:
> On Wed, 29 May 2024, Eric Auger wrote:
>> On 5/29/24 17:51, Sebastian Ott wrote:
>>> On Wed, 29 May 2024, Eric Auger wrote:
>>>>> @@ -3557,6 +3557,13 @@ void kvm_reset_sys_regs(struct kvm_vcpu *vcpu)
>>>>>      struct kvm *kvm = vcpu->kvm;
>>>>>      unsigned long i;
>>>>>
>>>>> +    if (!kvm_vcpu_initialized(vcpu))
>>>> at this stage of the reading, why is the above check needed?
>>>
>>> To make sure that a later call to this function doesn't overwrite
>>> the value provided by userspace. (See e016333745c "KVM: arm64: Only
>>> reset vCPU-scoped feature ID regs once").
>> but isn't it overwritten through the .reset=reset_ctr() that is
>> populated in next patch?
> 
> No, this is done via reset_vcpu_ftr_id_reg() and also guarded by
> kvm_vcpu_initialized().

OK thanks.

Eric
> 
> Sebastian