linux-kernel - Re: [RFC PATCH 1/2] KVM: arm64: nv: selftests: Add guest hypervisor test

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <9bb48635-ce40-4710-8c43-be10ef217d9d@os.amperecomputing.com>
Date: Wed, 19 Feb 2025 18:17:28 +0530
From: Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>
To: Marc Zyngier <maz@...nel.org>
Cc: kvm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 kvmarm@...ts.linux.dev, linux-kernel@...r.kernel.org,
 linux-kselftest@...r.kernel.org, oliver.upton@...ux.dev, joey.gouly@....com,
 suzuki.poulose@....com, darren@...amperecomputing.com,
 scott@...amperecomputing.com
Subject: Re: [RFC PATCH 1/2] KVM: arm64: nv: selftests: Add guest hypervisor
 test



On 07-02-2025 10:16 pm, Ganapatrao Kulkarni wrote:
> 
> 
> On 07-02-2025 07:29 pm, Marc Zyngier wrote:
>> On Fri, 07 Feb 2025 13:26:41 +0000,
>> Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com> wrote:
>>>
>>>>> +    if (is_vcpu_nested(vcpu)) {
>>>>> +        vcpu_set_reg(vcpu, KVM_ARM64_SYS_REG(SYS_CPTR_EL2), fpen);
>>>>> +        vcpu_set_reg(vcpu, KVM_ARM64_SYS_REG(SYS_SCTLR_EL2), 
>>>>> sctlr_el1);
>>>>> +        vcpu_set_reg(vcpu, KVM_ARM64_SYS_REG(SYS_TCR_EL2), tcr_el1);
>>>>> +        vcpu_set_reg(vcpu, KVM_ARM64_SYS_REG(SYS_MAIR_EL2), 
>>>>> DEFAULT_MAIR_EL1);
>>>>> +        vcpu_set_reg(vcpu, KVM_ARM64_SYS_REG(SYS_TTBR0_EL2), 
>>>>> ttbr0_el1);
>>>>> +        vcpu_set_reg(vcpu, KVM_ARM64_SYS_REG(SYS_TPIDR_EL2), vcpu- 
>>>>> >id);
>>>>
>>>> How about some of the basics such as HCR_EL2, MDCR_EL2? A bunch of
>>>> things there do have an impact on how the guest behaves, and relying
>>>> on defaults feels like a bad idea.
>>>
>>> Sure, I will try to have these registers also set to required value
>>> explicitly.
>>>
>>>>
>>>> This also assumes VHE, without trying to enforce it.
>>>
>>> Ok, I will try to set specific bits of HCR_EL2 to force it run in VHE.
>>>
>>>>
>>>> Finally, how to you plan to make all the existing tests run as EL2
>>>> guests if TPIDR_EL1 isn't populated with the expected value? Surely
>>>> you need to change the read side...
>>>

IIUC, we need not write to TPIDR_EL2, instead write always to TPIDR_EL1 
and in guest code(like function cpu_copy_el2regs in Linux kernel) copy 
TPIDR_EL1 value to TPIDR_EL2.

OR, Write to both TPIDR_EL1 and TPIDR_EL2 in the test code itself during 
vcpu setup.

-- 
Thanks,
Ganapat/GK