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Date: Mon, 5 Jan 2026 17:00:55 +0000
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Subject: Re: [PATCH v3 4/4] KVM: selftests: arm64: Skip all 32 bit IDs when
 set_id_regs is aarch64 only
To: Mark Brown <broonie@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>, Joey Gouly <joey.gouly@arm.com>,
 Suzuki K Poulose <suzuki.poulose@arm.com>,
 Paolo Bonzini <pbonzini@redhat.com>, Shuah Khan <shuah@kernel.org>,
 Oliver Upton <oupton@kernel.org>, linux-arm-kernel@lists.infradead.org,
 kvmarm@lists.linux.dev, kvm@vger.kernel.org,
 linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20251219-kvm-arm64-set-id-regs-aarch64-v3-0-bfa474ec3218@kernel.org>
 <20251219-kvm-arm64-set-id-regs-aarch64-v3-4-bfa474ec3218@kernel.org>
 <363e440d-4e29-4286-ade4-b4be2f856859@arm.com>
 <90fb25bd-fa79-4980-902b-497346a3e6d5@sirena.org.uk>
From: Ben Horgan <ben.horgan@arm.com>
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Hi Mark,

On 1/5/26 16:45, Mark Brown wrote:
> On Fri, Jan 02, 2026 at 02:50:07PM +0000, Ben Horgan wrote:
>> On 12/19/25 19:28, Mark Brown wrote:
> 
>>> +			if (aarch64_only && sys_reg_CRm(reg_id) < 4) {
>>> +				ksft_test_result_skip("%s value seen in guest\n",
>>> +						      get_reg_name(reg_id));
>>> +				break;
>>> +			}
>>> +
> 
>> Unnecessary? The decision for which regs are testing is made in
>> guest_code().
> 
> The guest code has a fixed list of registers it reads blindly and we
> skip the write for these so our expected value won't be something we
> explicitly set.  The actual test is done here in the host code and it
> seems both more maintainable to keep the skip adjacent to the live test
> and clearer to be more explicit about nothing actually being tested.

Thanks for the explanation, it seems like a sensible decision.

Ben