Re: KVM selftest for L2 guest execution fails

[Marc Zyngier <maz@kernel.org>]

On Wed, 30 Jul 2025 07:44:48 +0100,
Itaru Kitayama <itaru.kitayama@linux.dev> wrote:
> 
> Hi,
> My small kvm sefltest tested on the kvmarm/next with NV2+VHE on FVP fails:
> 
> # ./arm64/test5
> Random seed: 0x6b8b4567
> ==== Test Assertion Failure ====
>   lib/kvm_util.c:1746: !ret
>   pid=257 tid=257 errno=11 - Resource temporarily unavailable
> sh: line 1: addr2line: command not found
>   KVM_RUN failed, rc: -1 errno: 11 (Resource temporarily unavailable)
> 
> Below is the test code, am I doing still wrong?

Quite a lot is wrong there.

> 
> Thanks,
> Itaru.
> 
>  // SPDX-License-Identifier: GPL-2.0-only
> 
> #include "test_util.h"
> #include "kvm_util.h"
> #include "processor.h"
> #include "ucall.h"
> 
> #define GUEST_SYNC_VAL 0x1234
> #define UCALL_GPA 0x500000
> 
> static void l1_guest_code(void)
> {
>         /*
>         * Set up HCR_EL2 to enable virtualization and nested support:
>         *   - HCR_EL2.VM  = 1 (enable stage-2 translation)
>         *   - HCR_EL2.NV  = 1 (trap to EL2 on guest HVC, SMC, WFI, etc.)
>         *   - HCR_EL2.TGE = 1 (trap general exceptions in EL1 to EL2)

You really want to read the spec again -- this is not what this means.

>         */
>        uint64_t hcr = (1UL << 0)   |  // VM
>                       (1UL << 27)  |  // TGE
>                       (1UL << 31);    // NV

- You enable S2 translation, and yet don't setup anything related to it

- You have TGE set, and yet (try to) return to EL1

- You set NV, and yet don't have a VNCR_EL2 populated

I don't know what you are trying to do here, but this is pretty badly
thought out.

I'd suggest you start by having a simple L2, without making use of NV
at all in the guest. You will still have to have a stage-2 and a
correct HCR_EL2 configuration -- none of which is as trivial as this
test suggests.

Once that is actually working, you can go wild and enable NV. But not
before.

	M.

-- 
Without deviation from the norm, progress is not possible.