Re: [PATCH v3 2/6] KVM: arm64: maintain per VM value for CTR_EL0

From: Eric Auger <eauger@redhat.com>
To: Sebastian Ott <sebott@redhat.com>
Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev,
	linux-kernel@vger.kernel.org, Marc Zyngier <maz@kernel.org>,
	Oliver Upton <oliver.upton@linux.dev>,
	James Morse <james.morse@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>
Subject: Re: [PATCH v3 2/6] KVM: arm64: maintain per VM value for CTR_EL0
Date: Thu, 30 May 2024 14:17:33 +0200	[thread overview]
Message-ID: <897ea2fa-838a-4b33-8434-dba5dddaf9ca@redhat.com> (raw)
In-Reply-To: <a0295969-eff9-5330-cd1f-1e41b8f43eee@redhat.com>

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