linux-kernel - Re: [PATCH v9 13/43] arm64: RME: Support for the VGIC in realms

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Message-ID: <c7d5b038-70b3-4e55-a6bc-a74b77a04d3d@arm.com>
Date: Wed, 9 Jul 2025 15:42:57 +0100
From: Steven Price <steven.price@....com>
To: Suzuki K Poulose <suzuki.poulose@....com>, kvm@...r.kernel.org,
 kvmarm@...ts.linux.dev
Cc: Catalin Marinas <catalin.marinas@....com>, Marc Zyngier <maz@...nel.org>,
 Will Deacon <will@...nel.org>, James Morse <james.morse@....com>,
 Oliver Upton <oliver.upton@...ux.dev>, Zenghui Yu <yuzenghui@...wei.com>,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 Joey Gouly <joey.gouly@....com>, Alexandru Elisei
 <alexandru.elisei@....com>, Christoffer Dall <christoffer.dall@....com>,
 Fuad Tabba <tabba@...gle.com>, linux-coco@...ts.linux.dev,
 Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>,
 Gavin Shan <gshan@...hat.com>, Shanker Donthineni <sdonthineni@...dia.com>,
 Alper Gun <alpergun@...gle.com>, "Aneesh Kumar K . V"
 <aneesh.kumar@...nel.org>, Emi Kisanuki <fj0570is@...itsu.com>
Subject: Re: [PATCH v9 13/43] arm64: RME: Support for the VGIC in realms

On 03/07/2025 14:22, Suzuki K Poulose wrote:
> On 11/06/2025 11:48, Steven Price wrote:
>> The RMM provides emulation of a VGIC to the realm guest but delegates
>> much of the handling to the host. Implement support in KVM for
>> saving/restoring state to/from the REC structure.
>>
>> Signed-off-by: Steven Price <steven.price@....com>
>> ---
>> Changes from v8:
>>   * Propagate gicv3_hcr to from the RMM.
>> Changes from v5:
>>   * Handle RMM providing fewer GIC LRs than the hardware supports.
>> ---
>>   arch/arm64/include/asm/kvm_rme.h |  1 +
>>   arch/arm64/kvm/arm.c             | 16 +++++++++--
>>   arch/arm64/kvm/rme.c             |  5 ++++
>>   arch/arm64/kvm/vgic/vgic-init.c  |  2 +-
>>   arch/arm64/kvm/vgic/vgic-v3.c    |  6 +++-
>>   arch/arm64/kvm/vgic/vgic.c       | 49 ++++++++++++++++++++++++++++++--
>>   6 files changed, 72 insertions(+), 7 deletions(-)
>>
> 
> ...
> 
>> diff --git a/arch/arm64/kvm/vgic/vgic-init.c b/arch/arm64/kvm/vgic/
>> vgic-init.c
>> index eb1205654ac8..77b4962ebfb6 100644
>> --- a/arch/arm64/kvm/vgic/vgic-init.c
>> +++ b/arch/arm64/kvm/vgic/vgic-init.c
>> @@ -81,7 +81,7 @@ int kvm_vgic_create(struct kvm *kvm, u32 type)
>>        * the proper checks already.
>>        */
>>       if (type == KVM_DEV_TYPE_ARM_VGIC_V2 &&
>> -        !kvm_vgic_global_state.can_emulate_gicv2)
>> +        (!kvm_vgic_global_state.can_emulate_gicv2 || kvm_is_realm(kvm)))
>>           return -ENODEV;
>>         /*
>> diff --git a/arch/arm64/kvm/vgic/vgic-v3.c b/arch/arm64/kvm/vgic/vgic-
>> v3.c
>> index b9ad7c42c5b0..c10ad817030d 100644
>> --- a/arch/arm64/kvm/vgic/vgic-v3.c
>> +++ b/arch/arm64/kvm/vgic/vgic-v3.c
>> @@ -8,9 +8,11 @@
>>   #include <linux/kvm_host.h>
>>   #include <linux/string_choices.h>
>>   #include <kvm/arm_vgic.h>
>> +#include <asm/kvm_emulate.h>
>>   #include <asm/kvm_hyp.h>
>>   #include <asm/kvm_mmu.h>
>>   #include <asm/kvm_asm.h>
>> +#include <asm/rmi_smc.h>
>>     #include "vgic.h"
>>   @@ -758,7 +760,9 @@ void vgic_v3_put(struct kvm_vcpu *vcpu)
>>           return;
>>       }
>>   -    if (likely(!is_protected_kvm_enabled()))
>> +    if (vcpu_is_rec(vcpu))
>> +        cpu_if->vgic_vmcr = vcpu->arch.rec.run->exit.gicv3_vmcr;
>> +    else if (likely(!is_protected_kvm_enabled()))
> 
> This function is never reached for Realms, this should be folded in
> vgic_rmm_save_state(). See below.

Good catch - I can drop the changes in this file and handle VMCR in
vgic_rmm_save_state().

Thanks,
Steve

> 
>>           kvm_call_hyp(__vgic_v3_save_vmcr_aprs, cpu_if);
>>       WARN_ON(vgic_v4_put(vcpu));
>>   diff --git a/arch/arm64/kvm/vgic/vgic.c b/arch/arm64/kvm/vgic/vgic.c
>> index c7aed48c5668..2908b4610c4e 100644
>> --- a/arch/arm64/kvm/vgic/vgic.c
>> +++ b/arch/arm64/kvm/vgic/vgic.c
> 
> ...
> 
>>   void kvm_vgic_put(struct kvm_vcpu *vcpu)
>>   {
>> -    if (unlikely(!irqchip_in_kernel(vcpu->kvm) || !
>> vgic_initialized(vcpu->kvm))) {
>> +    if (unlikely(vcpu_is_rec(vcpu)))
>> +        return;
> 
> ^^^
> 
>> +    if (unlikely(!irqchip_in_kernel(vcpu->kvm) ||
>> +             !vgic_initialized(vcpu->kvm))) {
>>           if (has_vhe() &&
>> static_branch_unlikely(&kvm_vgic_global_state.gicv3_cpuif))
>>               __vgic_v3_deactivate_traps(&vcpu->arch.vgic_cpu.vgic_v3);
>>           return;
> 
> Suzuki