On Fri, Oct 02, 2026 at 10:53:58AM +1000, Gavin Shan wrote:
> On 9/4/26 5:35 AM, Mathieu Poirier wrote:
> > From: Jean-Philippe Brucker <[email protected]>
> >
> > The target code calls kvm_arm_vcpu_init() to mark the vCPU as part of a
> > Realm. For a Realm vCPU, only x0-x7 can be set at runtime. Before boot,
> > the PC can also be set, and is ignored at runtime. KVM also accepts a
> > few system register changes during initial configuration, as returned by
> > KVM_GET_REG_LIST.
> >
> > Signed-off-by: Jean-Philippe Brucker <[email protected]>
> > Signed-off-by: Mathieu Poirier <[email protected]>
> > ---
> > target/arm/cpu.h | 3 +++
> > target/arm/kvm-rme.c | 9 ++++++++
> > target/arm/kvm-stub.c | 5 ++++
> > target/arm/kvm.c | 54 +++++++++++++++++++++++++++++++++++++++++--
> > target/arm/kvm_arm.h | 10 ++++++++
> > 5 files changed, 79 insertions(+), 2 deletions(-)
> >
> > diff --git a/target/arm/cpu.h b/target/arm/cpu.h
> > index e3f931dba26b..6bbc942f9a59 100644
> > --- a/target/arm/cpu.h
> > +++ b/target/arm/cpu.h
> > @@ -1054,6 +1054,9 @@ struct ArchCPU {
> > /* KVM steal time */
> > OnOffAuto kvm_steal_time;
> > + /* Realm Management Extension */
> > + bool kvm_rme;
> > +
>
> This field seems redundant to MachineState::cgs since all vCPUs support RME
> (Realm Management Extension) when MachineState::cgs points a valid instance.
> So I'm wandering why we need to maintain the redundant information here?
>
It is redundant, at least at this time. I have removed it in favour of
MACHINE(qdev_get_machine())->cgs where cpu->kvm_rme was used. With that it was
possible to get rid of function kvm_arm_rme_vcpu_init().
> > /* Uniprocessor system with MP extensions */
> > bool mp_is_up;
> > diff --git a/target/arm/kvm-rme.c b/target/arm/kvm-rme.c
> > index a4a5e195c196..f7c2cc786e2c 100644
> > --- a/target/arm/kvm-rme.c
> > +++ b/target/arm/kvm-rme.c
> > @@ -69,6 +69,15 @@ static int kvm_arm_rme_init(ConfidentialGuestSupport
> > *cgs, Error **errp)
> > return 0;
> > }
> > +void kvm_arm_rme_vcpu_init(ARMCPU *cpu)
> > +{
> > + if (!rme_guest) {
> > + return;
> > + }
> > +
> > + cpu->kvm_rme = true;
> > +}
> > +
>
> This could be simplified to:
>
> cpu->kvm_rme = !!rme_guest;
>
> > static void rme_guest_class_init(ObjectClass *oc, const void *data)
> > {
> > ConfidentialGuestSupportClass *klass =
> > CONFIDENTIAL_GUEST_SUPPORT_CLASS(oc);
> > diff --git a/target/arm/kvm-stub.c b/target/arm/kvm-stub.c
> > index 88cbe8d85c41..5fde96f9b281 100644
> > --- a/target/arm/kvm-stub.c
> > +++ b/target/arm/kvm-stub.c
> > @@ -119,3 +119,8 @@ char *kvm_print_register_name(uint64_t regidx)
> > {
> > g_assert_not_reached();
> > }
> > +
> > +void kvm_arm_rme_vcpu_init(ARMCPU *cpu)
> > +{
> > + g_assert_not_reached();
> > +}
> > diff --git a/target/arm/kvm.c b/target/arm/kvm.c
> > index 33c3763aebfa..b4c6da1fb9f3 100644
> > --- a/target/arm/kvm.c
> > +++ b/target/arm/kvm.c
> > @@ -2015,6 +2015,8 @@ int kvm_arch_init_vcpu(CPUState *cs)
> > cpu->kvm_init_features[0] |= 1 << KVM_ARM_VCPU_HAS_EL2;
> > }
> > + kvm_arm_rme_vcpu_init(cpu);
> > +
> > /* Do KVM_ARM_VCPU_INIT ioctl */
> > ret = kvm_arm_vcpu_init(cpu);
> > if (ret) {
> > @@ -2169,6 +2171,29 @@ static int kvm_arch_put_sve(CPUState *cs, uint32_t
> > vq, bool have_ffr)
> > return 0;
> > }
> > +static int kvm_arm_rme_put_core_regs(CPUState *cs, Error **errp)
> > +{
> > + int i, ret;
> > + ARMCPU *cpu = ARM_CPU(cs);
> > + CPUARMState *env = &cpu->env;
> > +
> > + /* The RME ABI only allows us to set 8 GPRs and the PC */
> > + for (i = 0; i < 8; i++) {
> > + ret = kvm_set_one_reg(cs, AARCH64_CORE_REG(regs.regs[i]),
> > + &env->xregs[i]);
> > + if (ret) {
> > + return ret;
> > + }
> > + }
> > +
> > + ret = kvm_set_one_reg(cs, AARCH64_CORE_REG(regs.pc), &env->pc);
> > + if (ret) {
> > + return ret;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > static int kvm_arm_put_core_regs(CPUState *cs, Error **errp)
> > {
> > uint64_t val;
> > @@ -2280,7 +2305,11 @@ int kvm_arch_put_registers(CPUState *cs, KvmPutState
> > level, Error **errp)
> > int ret;
> > ARMCPU *cpu = ARM_CPU(cs);
> > - ret = kvm_arm_put_core_regs(cs, errp);
> > + if (cpu->kvm_rme) {
> > + ret = kvm_arm_rme_put_core_regs(cs, errp);
> > + } else {
> > + ret = kvm_arm_put_core_regs(cs, errp);
> > + }
> > if (ret) {
> > return ret;
> > }
> > @@ -2367,6 +2396,23 @@ static int kvm_arch_get_sve(CPUState *cs, uint32_t
> > vq, bool have_ffr)
> > return 0;
> > }
> > +static int kvm_arm_rme_get_core_regs(CPUState *cs, Error **errp)
> > +{
> > + int i, ret;
> > + ARMCPU *cpu = ARM_CPU(cs);
> > + CPUARMState *env = &cpu->env;
> > +
> > + for (i = 0; i < 8; i++) {
> > + ret = kvm_get_one_reg(cs, AARCH64_CORE_REG(regs.regs[i]),
> > + &env->xregs[i]);
> > + if (ret) {
> > + return ret;
> > + }
> > + }
> > +
> > + return 0;
> > +}
> > +
> > static int kvm_arm_get_core_regs(CPUState *cs, Error **errp)
> > {
> > uint64_t val;
> > @@ -2478,7 +2524,11 @@ int kvm_arch_get_registers(CPUState *cs, Error
> > **errp)
> > int ret;
> > ARMCPU *cpu = ARM_CPU(cs);
> > - ret = kvm_arm_get_core_regs(cs, errp);
> > + if (cpu->kvm_rme) {
> > + ret = kvm_arm_rme_get_core_regs(cs, errp);
> > + } else {
> > + ret = kvm_arm_get_core_regs(cs, errp);
> > + }
> > if (ret) {
> > return ret;
> > }
> > diff --git a/target/arm/kvm_arm.h b/target/arm/kvm_arm.h
> > index e7c40fb003e4..d95381c13afa 100644
> > --- a/target/arm/kvm_arm.h
> > +++ b/target/arm/kvm_arm.h
> > @@ -240,4 +240,14 @@ void arm_gic_cap_kvm_probe(GICCapability *v2,
> > GICCapability *v3);
> > */
> > char *kvm_print_register_name(uint64_t regidx);
> > +/**
> > + * kvm_arm_rme_vcpu_init
> > + * @cs: the CPU
> > + *
> > + * If the user requested a Realm, setup the given vCPU accordingly. Realm
> > vCPUs
> > + * behave a little differently, for example most of their register state is
> > + * hidden from the host.
> > + */
> > +void kvm_arm_rme_vcpu_init(ARMCPU *cpu);
> > +
>
> The comments here look outdated. This function simply set ARMCPU::kvm_rme to
> indicate
> RME should be supported for this given vCPU. So the comments would be
> something as
> below.
>
> /*
> *
> * Mark that RME (Realm Management Extension) should be supported for the
> given
> * vCPU if user has requested it. Realm vCPUs behave a little
> differently, for
> * example most of their register states are confidential and invisible
> to us.
> */
>
> > #endif
>
> Thanks,
> Gavin
>
