On 07/05/2025 11:26, Suzuki K Poulose wrote:
> On 16/04/2025 14:41, Steven Price wrote:
>> Entering a realm is done using a SMC call to the RMM. On exit the
>> exit-codes need to be handled slightly differently to the normal KVM
>> path so define our own functions for realm enter/exit and hook them
>> in if the guest is a realm guest.
>>
>> Signed-off-by: Steven Price <steven.price@xxxxxxx>
>> ---
>> Changes since v7:
>> * A return of 0 from kvm_handle_sys_reg() doesn't mean the register has
>> been read (although that can never happen in the current code). Tidy
>> up the condition to handle any future refactoring.
>> Changes since v6:
>> * Use vcpu_err() rather than pr_err/kvm_err when there is an associated
>> vcpu to the error.
>> * Return -EFAULT for KVM_EXIT_MEMORY_FAULT as per the documentation for
>> this exit type.
>> * Split code handling a RIPAS change triggered by the guest to the
>> following patch.
>> Changes since v5:
>> * For a RIPAS_CHANGE request from the guest perform the actual RIPAS
>> change on next entry rather than immediately on the exit. This allows
>> the VMM to 'reject' a RIPAS change by refusing to continue
>> scheduling.
>> Changes since v4:
>> * Rename handle_rme_exit() to handle_rec_exit()
>> * Move the loop to copy registers into the REC enter structure from the
>> to rec_exit_handlers callbacks to kvm_rec_enter(). This fixes a bug
>> where the handler exits to user space and user space wants to modify
>> the GPRS.
>> * Some code rearrangement in rec_exit_ripas_change().
>> Changes since v2:
>> * realm_set_ipa_state() now provides an output parameter for the
>> top_iap that was changed. Use this to signal the VMM with the correct
>> range that has been transitioned.
>> * Adapt to previous patch changes.
>> ---
>> arch/arm64/include/asm/kvm_rme.h | 3 +
>> arch/arm64/kvm/Makefile | 2 +-
>> arch/arm64/kvm/arm.c | 19 +++-
>> arch/arm64/kvm/rme-exit.c | 170 +++++++++++++++++++++++++++++++
>> arch/arm64/kvm/rme.c | 19 ++++
>> 5 files changed, 207 insertions(+), 6 deletions(-)
>> create mode 100644 arch/arm64/kvm/rme-exit.c
>>
>> diff --git a/arch/arm64/include/asm/kvm_rme.h b/arch/arm64/include/
>> asm/kvm_rme.h
>> index b916db8565a2..d86051ef0c5c 100644
>> --- a/arch/arm64/include/asm/kvm_rme.h
>> +++ b/arch/arm64/include/asm/kvm_rme.h
>> @@ -101,6 +101,9 @@ void kvm_realm_destroy_rtts(struct kvm *kvm, u32
>> ia_bits);
>> int kvm_create_rec(struct kvm_vcpu *vcpu);
>> void kvm_destroy_rec(struct kvm_vcpu *vcpu);
>> +int kvm_rec_enter(struct kvm_vcpu *vcpu);
>> +int handle_rec_exit(struct kvm_vcpu *vcpu, int rec_run_status);
>> +
>> void kvm_realm_unmap_range(struct kvm *kvm,
>> unsigned long ipa,
>> unsigned long size,
>> diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
>> index 2ebc66812d49..c4b10012faa3 100644
>> --- a/arch/arm64/kvm/Makefile
>> +++ b/arch/arm64/kvm/Makefile
>> @@ -24,7 +24,7 @@ kvm-y += arm.o mmu.o mmio.o psci.o hypercalls.o
>> pvtime.o \
>> vgic/vgic-mmio.o vgic/vgic-mmio-v2.o \
>> vgic/vgic-mmio-v3.o vgic/vgic-kvm-device.o \
>> vgic/vgic-its.o vgic/vgic-debug.o vgic/vgic-v3-nested.o \
>> - rme.o
>> + rme.o rme-exit.o
>> kvm-$(CONFIG_HW_PERF_EVENTS) += pmu-emul.o pmu.o
>> kvm-$(CONFIG_ARM64_PTR_AUTH) += pauth.o
>> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
>> index 7c0bb1b05f4c..cf707130ef66 100644
>> --- a/arch/arm64/kvm/arm.c
>> +++ b/arch/arm64/kvm/arm.c
>> @@ -1263,7 +1263,10 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
>> trace_kvm_entry(*vcpu_pc(vcpu));
>> guest_timing_enter_irqoff();
>> - ret = kvm_arm_vcpu_enter_exit(vcpu);
>> + if (vcpu_is_rec(vcpu))
>> + ret = kvm_rec_enter(vcpu);
>> + else
>> + ret = kvm_arm_vcpu_enter_exit(vcpu);
>> vcpu->mode = OUTSIDE_GUEST_MODE;
>> vcpu->stat.exits++;
>> @@ -1319,10 +1322,13 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu
>> *vcpu)
>> local_irq_enable();
>> - trace_kvm_exit(ret, kvm_vcpu_trap_get_class(vcpu),
>> *vcpu_pc(vcpu));
>> -
>> /* Exit types that need handling before we can be preempted */
>> - handle_exit_early(vcpu, ret);
>> + if (!vcpu_is_rec(vcpu)) {
>> + trace_kvm_exit(ret, kvm_vcpu_trap_get_class(vcpu),
>> + *vcpu_pc(vcpu));
>> +
>> + handle_exit_early(vcpu, ret);
>> + }
>
> minor nit: Looks like we loose the kvm_exit trace. Could we add
> something in handle_rec_exit ?
I dropped the trace because we can't provide the PC value. I'm not sure
what's best here:
(1). Provide kvm_exit trace but with a bogus PC.
(2). Introduce a new 'kvm_rec_exit'.
(3). Wait until someone comes along with a use-case and hope they
implement what they need.
Obviously my preference is 3 ;)
In practice I haven't actually dropped kvm_entry (so that has a bogus
PC), so for now I guess I'll go with (1).
>> preempt_enable();
>> @@ -1345,7 +1351,10 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu
>> *vcpu)
>> ret = ARM_EXCEPTION_IL;
>> }
>> - ret = handle_exit(vcpu, ret);
>> + if (vcpu_is_rec(vcpu))
>> + ret = handle_rec_exit(vcpu, ret);
>> + else
>> + ret = handle_exit(vcpu, ret);
>> }
>> /* Tell userspace about in-kernel device output levels */
>> diff --git a/arch/arm64/kvm/rme-exit.c b/arch/arm64/kvm/rme-exit.c
>> new file mode 100644
>> index 000000000000..a1adf5610455
>> --- /dev/null
>> +++ b/arch/arm64/kvm/rme-exit.c
>> @@ -0,0 +1,170 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * Copyright (C) 2023 ARM Ltd.
>> + */
>> +
>> +#include <linux/kvm_host.h>
>> +#include <kvm/arm_hypercalls.h>
>> +#include <kvm/arm_psci.h>
>> +
>> +#include <asm/rmi_smc.h>
>> +#include <asm/kvm_emulate.h>
>> +#include <asm/kvm_rme.h>
>> +#include <asm/kvm_mmu.h>
>> +
>> +typedef int (*exit_handler_fn)(struct kvm_vcpu *vcpu);
>> +
>> +static int rec_exit_reason_notimpl(struct kvm_vcpu *vcpu)
>> +{
>> + struct realm_rec *rec = &vcpu->arch.rec;
>> +
>> + vcpu_err(vcpu, "Unhandled exit reason from realm (ESR: %#llx)\n",
>> + rec->run->exit.esr);
>> + return -ENXIO;
>> +}
>> +
>> +static int rec_exit_sync_dabt(struct kvm_vcpu *vcpu)
>> +{
>> + return kvm_handle_guest_abort(vcpu);
>> +}
>> +
>> +static int rec_exit_sync_iabt(struct kvm_vcpu *vcpu)
>> +{
>> + struct realm_rec *rec = &vcpu->arch.rec;
>> +
>> + vcpu_err(vcpu, "Unhandled instruction abort (ESR: %#llx).\n",
>> + rec->run->exit.esr);
>> + return -ENXIO;
>> +}
>> +
>> +static int rec_exit_sys_reg(struct kvm_vcpu *vcpu)
>> +{
>> + struct realm_rec *rec = &vcpu->arch.rec;
>> + unsigned long esr = kvm_vcpu_get_esr(vcpu);
>> + int rt = kvm_vcpu_sys_get_rt(vcpu);
>> + bool is_write = !(esr & 1);
>> + int ret;
>> +
>> + if (is_write)
>> + vcpu_set_reg(vcpu, rt, rec->run->exit.gprs[0]);
>> +
>> + ret = kvm_handle_sys_reg(vcpu);
>> + if (ret > 0 && !is_write)
>> + rec->run->enter.gprs[0] = vcpu_get_reg(vcpu, rt);
>> +
>> + return ret;
>> +}
>> +
>> +static exit_handler_fn rec_exit_handlers[] = {
>> + [0 ... ESR_ELx_EC_MAX] = rec_exit_reason_notimpl,
>> + [ESR_ELx_EC_SYS64] = rec_exit_sys_reg,
>> + [ESR_ELx_EC_DABT_LOW] = rec_exit_sync_dabt,
>> + [ESR_ELx_EC_IABT_LOW] = rec_exit_sync_iabt
>> +};
>> +
>> +static int rec_exit_psci(struct kvm_vcpu *vcpu)
>> +{
>> + struct realm_rec *rec = &vcpu->arch.rec;
>> + int i;
>> +
>> + for (i = 0; i < REC_RUN_GPRS; i++)
>> + vcpu_set_reg(vcpu, i, rec->run->exit.gprs[i]);
>> +
>> + return kvm_smccc_call_handler(vcpu);
>> +}
>> +
>> +static int rec_exit_ripas_change(struct kvm_vcpu *vcpu)
>> +{
>> + struct kvm *kvm = vcpu->kvm;
>> + struct realm *realm = &kvm->arch.realm;
>> + struct realm_rec *rec = &vcpu->arch.rec;
>> + unsigned long base = rec->run->exit.ripas_base;
>> + unsigned long top = rec->run->exit.ripas_top;
>> + unsigned long ripas = rec->run->exit.ripas_value;
>> +
>> + if (!kvm_realm_is_private_address(realm, base) ||
>> + !kvm_realm_is_private_address(realm, top - 1)) {
>> + vcpu_err(vcpu, "Invalid RIPAS_CHANGE for %#lx - %#lx, ripas:
>> %#lx\n",
>> + base, top, ripas);
>
> Do we need to set the RMI_REJECT for run->enter.flags
> REC_ENTER_FLAG_RIPAS_RESPONSE ?
Makes sense, will add.
Thanks,
Steve
> Rest looks fine to me.
>
> Suzuki
