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Message-ID: <82c0ee14-65fb-4f34-892a-a3820d8d0f97@arm.com>
Date: Wed, 7 May 2025 11:26:14 +0100
From: Suzuki K Poulose <suzuki.poulose@....com>
To: Steven Price <steven.price@....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>
Subject: Re: [PATCH v8 16/43] arm64: RME: Handle realm enter/exit
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@....com>
> ---
> 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 ?
>
> 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 ?
Rest looks fine to me.
Suzuki
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