On 16/06/2025 12:55, Gavin Shan wrote:
> Hi Steven,
>
> On 6/11/25 8:48 PM, Steven Price wrote:
>> At runtime if the realm guest accesses memory which hasn't yet been
>> mapped then KVM needs to either populate the region or fault the guest.
>>
>> For memory in the lower (protected) region of IPA a fresh page is
>> provided to the RMM which will zero the contents. For memory in the
>> upper (shared) region of IPA, the memory from the memslot is mapped
>> into the realm VM non secure.
>>
>> Signed-off-by: Steven Price <steven.price@xxxxxxx>
>> ---
>> arch/arm64/include/asm/kvm_emulate.h | 10 ++
>> arch/arm64/include/asm/kvm_rme.h | 10 ++
>> arch/arm64/kvm/mmu.c | 133 ++++++++++++++++++++-
>> arch/arm64/kvm/rme.c | 165 +++++++++++++++++++++++++++
>> 4 files changed, 312 insertions(+), 6 deletions(-)
>>
>
> [...]
>
>> @@ -1078,6 +1091,9 @@ void kvm_free_stage2_pgd(struct kvm_s2_mmu *mmu)
>> if (kvm_is_realm(kvm) &&
>> (kvm_realm_state(kvm) != REALM_STATE_DEAD &&
>> kvm_realm_state(kvm) != REALM_STATE_NONE)) {
>> + struct realm *realm = &kvm->arch.realm;
>> +
>> + kvm_stage2_unmap_range(mmu, 0, BIT(realm->ia_bits - 1), false);
>> write_unlock(&kvm->mmu_lock);
>> kvm_realm_destroy_rtts(kvm, pgt->ia_bits);
>>
>
> I'm giving it a try before taking time to review, @may_block needs to be
> true.
> I don't see there is anything why not to do so :)
You are right - I've no idea why I passed false to may_block. Thanks for
the report.
Thanks,
Steve
> kvm_stage2_unmap_range(mmu, 0, BIT(realm->ia_bits - 1), true);
>
> Otherwise, there is RCU stall when the VM is destroyed.
>
> [12730.399825] rcu: INFO: rcu_preempt self-detected stall on CPU
> [12730.401922] rcu: 5-....: (5165 ticks this GP)
> idle=3544/1/0x4000000000000000 softirq=41673/46605 fqs=2625
> [12730.404598] rcu: (t=5251 jiffies g=61757 q=36 ncpus=8)
> [12730.406771] CPU: 5 UID: 0 PID: 170 Comm: qemu-system-aar Not tainted
> 6.16.0-rc1-gavin-gfbc56042a9cf #36 PREEMPT
> [12730.407918] Hardware name: QEMU QEMU Virtual Machine, BIOS unknown
> 02/02/2022
> [12730.408796] pstate: 61402009 (nZCv daif +PAN -UAO -TCO +DIT -SSBS
> BTYPE=--)
> [12730.409515] pc : realm_unmap_private_range+0x1b4/0x310
> [12730.410825] lr : realm_unmap_private_range+0x98/0x310
> [12730.411377] sp : ffff8000808f3920
> [12730.411777] x29: ffff8000808f3920 x28: 0000000104d29000 x27:
> 000000004229b000
> [12730.413410] x26: 0000000000000000 x25: ffffb8c82d23f000 x24:
> 00007fffffffffff
> [12730.414292] x23: 000000004229c000 x22: 0001000000000000 x21:
> ffff80008019deb8
> [12730.415229] x20: 0000000101b3f000 x19: 000000004229b000 x18:
> ffff8000808f3bd0
> [12730.416119] x17: 0000000000000001 x16: ffffffffffffffff x15:
> 0000ffff91cc5000
> [12730.417004] x14: ffffb8c82cfccb48 x13: 0000ffff4b1fffff x12:
> 0000000000000000
> [12730.417876] x11: 0000000038e38e39 x10: 0000000000000004 x9 :
> ffffb8c82c39a030
> [12730.418863] x8 : ffff80008019deb8 x7 : 0000010000000000 x6 :
> 0000000000000000
> [12730.419738] x5 : 0000000038e38e39 x4 : ffff0000c0d80000 x3 :
> 0000000000000000
> [12730.420609] x2 : 000000004229c000 x1 : 0000000104d2a000 x0 :
> 0000000000000000
> [12730.421602] Call trace:
> [12730.422209] realm_unmap_private_range+0x1b4/0x310 (P)
> [12730.423096] kvm_realm_unmap_range+0xbc/0xe0
> [12730.423657] __unmap_stage2_range+0x74/0xa8
> [12730.424198] kvm_free_stage2_pgd+0xc8/0x120
> [12730.424746] kvm_uninit_stage2_mmu+0x24/0x48
> [12730.425284] kvm_arch_flush_shadow_all+0x74/0x98
> [12730.425849] kvm_mmu_notifier_release+0x38/0xa0
> [12730.426409] __mmu_notifier_release+0x80/0x1f0
> [12730.427031] exit_mmap+0x3d8/0x438
> [12730.427526] __mmput+0x38/0x160
> [12730.428000] mmput+0x58/0x78
> [12730.428463] do_exit+0x210/0x9d8
> [12730.428945] do_group_exit+0x3c/0xa0
> [12730.429458] get_signal+0x8d4/0x9c0
> [12730.429954] do_signal+0x98/0x400
> [12730.430455] do_notify_resume+0xec/0x1a0
> [12730.431030] el0_svc+0xe8/0x130
> [12730.431536] el0t_64_sync_handler+0x10c/0x138
> [12730.432085] el0t_64_sync+0x1ac/0x1b0
>
> Thanks,
> Gavin
>
