Re: [RFC PATCH 10/28] arm64: RME: Allocate/free RECs to match vCPUs

Zhi Wang
2023-02-13T18:09:31Z

On Fri, 27 Jan 2023 11:29:14 +0000
Steven Price <steven.price@arm.com> wrote:

> The RMM maintains a data structure known as the Realm Execution Context
> (or REC). It is similar to struct kvm_vcpu and tracks the state of the
> virtual CPUs. KVM must delegate memory and request the structures are
> created when vCPUs are created, and suitably tear down on destruction.
>

It would be better to leave some pointers to the spec here. It really saves
time for reviewers.

> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
> arch/arm64/include/asm/kvm_emulate.h | 2 +
> arch/arm64/include/asm/kvm_host.h | 3 +
> arch/arm64/include/asm/kvm_rme.h | 10 ++
> arch/arm64/kvm/arm.c | 1 +
> arch/arm64/kvm/reset.c | 11 ++
> arch/arm64/kvm/rme.c | 144 +++++++++++++++++++++++++++
> 6 files changed, 171 insertions(+)
>
> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
> index 5a2b7229e83f..285e62914ca4 100644
> --- a/arch/arm64/include/asm/kvm_emulate.h
> +++ b/arch/arm64/include/asm/kvm_emulate.h
> @@ -504,6 +504,8 @@ static inline enum realm_state kvm_realm_state(struct kvm *kvm)
>
> static inline bool vcpu_is_rec(struct kvm_vcpu *vcpu)
> {
> + if (static_branch_unlikely(&kvm_rme_is_available))
> + return vcpu->arch.rec.mpidr != INVALID_HWID;
> return false;
> }
>
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 04347c3a8c6b..ef497b718cdb 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -505,6 +505,9 @@ struct kvm_vcpu_arch {
> u64 last_steal;
> gpa_t base;
> } steal;
> +
> + /* Realm meta data */
> + struct rec rec;

I think the name of the data structure "rec" needs a prefix, it is too common
and might conflict with the private data structures in the other modules. Maybe
rme_rec or realm_rec?
> };
>
> /*
> diff --git a/arch/arm64/include/asm/kvm_rme.h b/arch/arm64/include/asm/kvm_rme.h
> index eea5118dfa8a..4b219ebe1400 100644
> --- a/arch/arm64/include/asm/kvm_rme.h
> +++ b/arch/arm64/include/asm/kvm_rme.h
> @@ -6,6 +6,7 @@
> #ifndef __ASM_KVM_RME_H
> #define __ASM_KVM_RME_H
>
> +#include <asm/rmi_smc.h>
> #include <uapi/linux/kvm.h>
>
> enum realm_state {
> @@ -29,6 +30,13 @@ struct realm {
> unsigned int ia_bits;
> };
>
> +struct rec {
> + unsigned long mpidr;
> + void *rec_page;
> + struct page *aux_pages[REC_PARAMS_AUX_GRANULES];
> + struct rec_run *run;
> +};
> +

It is better to leave some comments for above members or pointers to the spec,
that saves a lot of time for review.

> int kvm_init_rme(void);
> u32 kvm_realm_ipa_limit(void);
>
> @@ -36,6 +44,8 @@ int kvm_realm_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap);
> int kvm_init_realm_vm(struct kvm *kvm);
> void kvm_destroy_realm(struct kvm *kvm);
> void kvm_realm_destroy_rtts(struct realm *realm, u32 ia_bits, u32 start_level);
> +int kvm_create_rec(struct kvm_vcpu *vcpu);
> +void kvm_destroy_rec(struct kvm_vcpu *vcpu);
>
> #define RME_RTT_BLOCK_LEVEL 2
> #define RME_RTT_MAX_LEVEL 3
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index badd775547b8..52affed2f3cf 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -373,6 +373,7 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
> /* Force users to call KVM_ARM_VCPU_INIT */
> vcpu->arch.target = -1;
> bitmap_zero(vcpu->arch.features, KVM_VCPU_MAX_FEATURES);
> + vcpu->arch.rec.mpidr = INVALID_HWID;
>
> vcpu->arch.mmu_page_cache.gfp_zero = __GFP_ZERO;
>
> diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
> index 9e71d69e051f..0c84392a4bf2 100644
> --- a/arch/arm64/kvm/reset.c
> +++ b/arch/arm64/kvm/reset.c
> @@ -135,6 +135,11 @@ int kvm_arm_vcpu_finalize(struct kvm_vcpu *vcpu, int feature)
> return -EPERM;
>
> return kvm_vcpu_finalize_sve(vcpu);
> + case KVM_ARM_VCPU_REC:
> + if (!kvm_is_realm(vcpu->kvm))
> + return -EINVAL;
> +
> + return kvm_create_rec(vcpu);
> }
>
> return -EINVAL;
> @@ -145,6 +150,11 @@ bool kvm_arm_vcpu_is_finalized(struct kvm_vcpu *vcpu)
> if (vcpu_has_sve(vcpu) && !kvm_arm_vcpu_sve_finalized(vcpu))
> return false;
>
> + if (kvm_is_realm(vcpu->kvm) &&
> + !(vcpu_is_rec(vcpu) &&
> + READ_ONCE(vcpu->kvm->arch.realm.state) == REALM_STATE_ACTIVE))
> + return false;

That's why it is better to introduce the realm state in the previous patches so
that people can really get the idea of the states at this stage.

> +
> return true;
> }
>
> @@ -157,6 +167,7 @@ void kvm_arm_vcpu_destroy(struct kvm_vcpu *vcpu)
> if (sve_state)
> kvm_unshare_hyp(sve_state, sve_state + vcpu_sve_state_size(vcpu));
> kfree(sve_state);
> + kvm_destroy_rec(vcpu);
> }
>
> static void kvm_vcpu_reset_sve(struct kvm_vcpu *vcpu)
> diff --git a/arch/arm64/kvm/rme.c b/arch/arm64/kvm/rme.c
> index f7b0e5a779f8..d79ed889ca4d 100644
> --- a/arch/arm64/kvm/rme.c
> +++ b/arch/arm64/kvm/rme.c
> @@ -514,6 +514,150 @@ void kvm_destroy_realm(struct kvm *kvm)
> kvm_free_stage2_pgd(&kvm->arch.mmu);
> }
>
> +static void free_rec_aux(struct page **aux_pages,
> + unsigned int num_aux)
> +{
> + unsigned int i;
> +
> + for (i = 0; i < num_aux; i++) {
> + phys_addr_t aux_page_phys = page_to_phys(aux_pages[i]);
> +
> + if (WARN_ON(rmi_granule_undelegate(aux_page_phys)))
> + continue;
> +
> + __free_page(aux_pages[i]);
> + }
> +}
> +
> +static int alloc_rec_aux(struct page **aux_pages,
> + u64 *aux_phys_pages,
> + unsigned int num_aux)
> +{
> + int ret;
> + unsigned int i;
> +
> + for (i = 0; i < num_aux; i++) {
> + struct page *aux_page;
> + phys_addr_t aux_page_phys;
> +
> + aux_page = alloc_page(GFP_KERNEL);
> + if (!aux_page) {
> + ret = -ENOMEM;
> + goto out_err;
> + }
> + aux_page_phys = page_to_phys(aux_page);
> + if (rmi_granule_delegate(aux_page_phys)) {
> + __free_page(aux_page);
> + ret = -ENXIO;
> + goto out_err;
> + }
> + aux_pages[i] = aux_page;
> + aux_phys_pages[i] = aux_page_phys;
> + }
> +
> + return 0;
> +out_err:
> + free_rec_aux(aux_pages, i);
> + return ret;
> +}
> +
> +int kvm_create_rec(struct kvm_vcpu *vcpu)
> +{
> + struct user_pt_regs *vcpu_regs = vcpu_gp_regs(vcpu);
> + unsigned long mpidr = kvm_vcpu_get_mpidr_aff(vcpu);
> + struct realm *realm = &vcpu->kvm->arch.realm;
> + struct rec *rec = &vcpu->arch.rec;
> + unsigned long rec_page_phys;
> + struct rec_params *params;
> + int r, i;
> +
> + if (kvm_realm_state(vcpu->kvm) != REALM_STATE_NEW)
> + return -ENOENT;
> +
> + /*
> + * The RMM will report PSCI v1.0 to Realms and the KVM_ARM_VCPU_PSCI_0_2
> + * flag covers v0.2 and onwards.
> + */
> + if (!test_bit(KVM_ARM_VCPU_PSCI_0_2, vcpu->arch.features))
> + return -EINVAL;
> +
> + BUILD_BUG_ON(sizeof(*params) > PAGE_SIZE);
> + BUILD_BUG_ON(sizeof(*rec->run) > PAGE_SIZE);
> +
> + params = (struct rec_params *)get_zeroed_page(GFP_KERNEL);
> + rec->rec_page = (void *)__get_free_page(GFP_KERNEL);
> + rec->run = (void *)get_zeroed_page(GFP_KERNEL);
> + if (!params || !rec->rec_page || !rec->run) {
> + r = -ENOMEM;
> + goto out_free_pages;
> + }
> +
> + for (i = 0; i < ARRAY_SIZE(params->gprs); i++)
> + params->gprs[i] = vcpu_regs->regs[i];
> +
> + params->pc = vcpu_regs->pc;
> +
> + if (vcpu->vcpu_id == 0)
> + params->flags |= REC_PARAMS_FLAG_RUNNABLE;
> +
> + rec_page_phys = virt_to_phys(rec->rec_page);
> +
> + if (rmi_granule_delegate(rec_page_phys)) {
> + r = -ENXIO;
> + goto out_free_pages;
> + }
> +

Wouldn't it be better to extend the alloc_rec_aux() to allocate and delegate
pages above? so that you can same some gfps and rmi_granuale_delegates().

> + r = alloc_rec_aux(rec->aux_pages, params->aux, realm->num_aux);
> + if (r)
> + goto out_undelegate_rmm_rec;
> +
> + params->num_rec_aux = realm->num_aux;
> + params->mpidr = mpidr;
> +
> + if (rmi_rec_create(rec_page_phys,
> + virt_to_phys(realm->rd),
> + virt_to_phys(params))) {
> + r = -ENXIO;
> + goto out_free_rec_aux;
> + }
> +
> + rec->mpidr = mpidr;
> +
> + free_page((unsigned long)params);
> + return 0;
> +
> +out_free_rec_aux:
> + free_rec_aux(rec->aux_pages, realm->num_aux);
> +out_undelegate_rmm_rec:
> + if (WARN_ON(rmi_granule_undelegate(rec_page_phys)))
> + rec->rec_page = NULL;
> +out_free_pages:
> + free_page((unsigned long)rec->run);
> + free_page((unsigned long)rec->rec_page);
> + free_page((unsigned long)params);
> + return r;
> +}
> +
> +void kvm_destroy_rec(struct kvm_vcpu *vcpu)
> +{
> + struct realm *realm = &vcpu->kvm->arch.realm;
> + struct rec *rec = &vcpu->arch.rec;
> + unsigned long rec_page_phys;
> +
> + if (!vcpu_is_rec(vcpu))
> + return;
> +
> + rec_page_phys = virt_to_phys(rec->rec_page);
> +
> + if (WARN_ON(rmi_rec_destroy(rec_page_phys)))
> + return;
> + if (WARN_ON(rmi_granule_undelegate(rec_page_phys)))
> + return;
> +

The two returns above feels off. What is the reason to skip the below page
undelegates?

> + free_rec_aux(rec->aux_pages, realm->num_aux);
> + free_page((unsigned long)rec->rec_page);
> +}
> +
> int kvm_init_realm_vm(struct kvm *kvm)
> {
> struct realm_params *params;