* KVM selftest for L2 guest execution fails
@ 2025-07-30 6:44 Itaru Kitayama
2025-07-30 12:24 ` Marc Zyngier
0 siblings, 1 reply; 3+ messages in thread
From: Itaru Kitayama @ 2025-07-30 6:44 UTC (permalink / raw)
To: kvmarm
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?
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)
*/
uint64_t hcr = (1UL << 0) | // VM
(1UL << 27) | // TGE
(1UL << 31); // NV
uint64_t spsr = 0x3c5; // EL1h, AArch64, interrupts masked
uint64_t l2_pc = 0x500000; // L2 guest entry address
uint64_t l2_sp = 0x510000; // L2 guest stack
__asm__ volatile(
// Set up EL2 to EL1 return
"msr hcr_el2, %[hcr]\n"
"msr elr_el2, %[el1_pc]\n"
"msr spsr_el2, %[spsr]\n"
"mov sp, %[el1_sp]\n"
"eret\n"
:
: [hcr] "r"(hcr),
[el1_pc] "r"(l2_pc),
[spsr] "r"(spsr),
[el1_sp] "r"(l2_sp)
: "memory"
);
}
static void l2_guest(void)
{
asm volatile(
"mov x0, #0x2a\n\t"
"mov x1, %[ucall_sync]\n\t"
"hvc #0\n\t"
:
: [ucall_sync] "i"(UCALL_SYNC)
: "x0", "x1"
);
}
static void guest_code()
{
GUEST_SYNC(42);
}
int main(void)
{
struct kvm_vm *vm;
struct kvm_vcpu *vcpu;
struct kvm_vcpu_init init = {};
u64 feat = 0;
/* NV2 must be supported or we skip */
if (!kvm_check_cap(KVM_CAP_ARM_EL2))
exit(KSFT_SKIP);
feat |= BIT(KVM_ARM_VCPU_HAS_EL2); // Ask for virtual EL2
vm = vm_create(1);
vm_ioctl(vm, KVM_ARM_PREFERRED_TARGET, &init);
init.features[0] = feat;
vcpu = aarch64_vcpu_add(vm, 0, &init, l1_guest_code);
// Backing memory for ucalls
virt_pg_map(vm, UCALL_GPA, UCALL_GPA);
ucall_init(vm, UCALL_GPA);
#define L2_MEM_START 0x500000
#define L2_MEM_SIZE 0x20000 // 128KB is enough
vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS, L2_MEM_START, 12, L2_MEM_SIZE / vm->page_size, KVM_MEM_LOG_DIRTY_PAGES);
virt_pg_map(vm, 0x500000, 0x500000); // L2 code
virt_pg_map(vm, 0x510000, 0x510000); // L2 stack
memcpy(addr_gpa2hva(vm, 0x500000), l2_guest, vm->page_size);
vcpu_run(vcpu);
printf("vcpu_run exited: reason = %u\n", vcpu->run->exit_reason);
struct ucall uc;
switch (get_ucall(vcpu, &uc)) {
case UCALL_SYNC:
printf("Guest sync: val = 0x%lx\n", uc.args[1]);
break;
case UCALL_DONE:
printf("Guest done\n");
break;
default:
TEST_FAIL("Unknown ucall %lu\n", uc.cmd);
}
return 0;
}
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: KVM selftest for L2 guest execution fails
2025-07-30 6:44 KVM selftest for L2 guest execution fails Itaru Kitayama
@ 2025-07-30 12:24 ` Marc Zyngier
2025-07-30 21:40 ` Itaru Kitayama
0 siblings, 1 reply; 3+ messages in thread
From: Marc Zyngier @ 2025-07-30 12:24 UTC (permalink / raw)
To: Itaru Kitayama; +Cc: kvmarm
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.
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: KVM selftest for L2 guest execution fails
2025-07-30 12:24 ` Marc Zyngier
@ 2025-07-30 21:40 ` Itaru Kitayama
0 siblings, 0 replies; 3+ messages in thread
From: Itaru Kitayama @ 2025-07-30 21:40 UTC (permalink / raw)
To: Marc Zyngier; +Cc: kvmarm
Hi Marc,
> On Jul 30, 2025, at 21:24, Marc Zyngier <maz@kernel.org> wrote:
>
> 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.
Thanks for your comments. Will follow your suggestions.
Itaru.
>
> M.
>
> --
> Without deviation from the norm, progress is not possible.
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2025-07-30 21:40 UTC | newest]
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2025-07-30 6:44 KVM selftest for L2 guest execution fails Itaru Kitayama
2025-07-30 12:24 ` Marc Zyngier
2025-07-30 21:40 ` Itaru Kitayama
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