Subject: Re: [RFC v1 2/2] KVM: PPC: Book3S HV: abstract secure VM related calls.

From: Bharata B Rao <[email-masked]>
Date: Mon, 12 Oct 2020 20:58:36 +0530

On Mon, Oct 12, 2020 at 12:27:43AM -0700, Ram Pai wrote:
> Abstract the secure VM related calls into generic calls.
> 
> These generic calls will call the corresponding method of the
> backend that prvoides the implementation to support secure VM.
> 
> Currently there is only the ultravisor based implementation.
> Modify that implementation to act as a backed to the generic calls.
> 
> This plumbing will provide the flexibility to add more backends
> in the future.
> 
> Signed-off-by: Ram Pai <[email-masked]>
> ---
>  arch/powerpc/include/asm/kvm_book3s_uvmem.h   | 100 -----------
>  arch/powerpc/include/asm/kvmppc_svm_backend.h | 250 ++++++++++++++++++++++++++
>  arch/powerpc/kvm/book3s_64_mmu_radix.c        |   6 +-
>  arch/powerpc/kvm/book3s_hv.c                  |  28 +--
>  arch/powerpc/kvm/book3s_hv_uvmem.c            |  78 ++++++--
>  5 files changed, 327 insertions(+), 135 deletions(-)
>  delete mode 100644 arch/powerpc/include/asm/kvm_book3s_uvmem.h
>  create mode 100644 arch/powerpc/include/asm/kvmppc_svm_backend.h
> 
> diff --git a/arch/powerpc/include/asm/kvmppc_svm_backend.h b/arch/powerpc/include/asm/kvmppc_svm_backend.h
> new file mode 100644
> index 0000000..be60d80
> --- /dev/null
> +++ b/arch/powerpc/include/asm/kvmppc_svm_backend.h
> @@ -0,0 +1,250 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + *
> + * Copyright IBM Corp. 2020
> + *
> + * Authors: Ram Pai <[email-masked]>
> + */
> +
> +#ifndef __POWERPC_KVMPPC_SVM_BACKEND_H__
> +#define __POWERPC_KVMPPC_SVM_BACKEND_H__
> +
> +#include <linux/mutex.h>
> +#include <linux/timer.h>
> +#include <linux/types.h>
> +#include <linux/kvm_types.h>
> +#include <linux/kvm_host.h>
> +#include <linux/bug.h>
> +#ifdef CONFIG_PPC_BOOK3S
> +#include <asm/kvm_book3s.h>
> +#else
> +#include <asm/kvm_booke.h>
> +#endif
> +#ifdef CONFIG_KVM_BOOK3S_64_HANDLER
> +#include <asm/paca.h>
> +#include <asm/xive.h>
> +#include <asm/cpu_has_feature.h>
> +#endif
> +
> +struct kvmppc_hmm_backend {

Though we started with HMM initially, what we ended up with eventually
has nothing to do with HMM. Please don't introduce hmm again :-)

> +	/* initialize */
> +	int (*kvmppc_secmem_init)(void);
> +
> +	/* cleanup */
> +	void (*kvmppc_secmem_free)(void);
> +
> +	/* is memory available */
> +	bool (*kvmppc_secmem_available)(void);
> +
> +	/* allocate a protected/secure page for the secure VM */
> +	unsigned long (*kvmppc_svm_page_in)(struct kvm *kvm,
> +			unsigned long gra,
> +			unsigned long flags,
> +			unsigned long page_shift);
> +
> +	/* recover the protected/secure page from the secure VM */
> +	unsigned long (*kvmppc_svm_page_out)(struct kvm *kvm,
> +			unsigned long gra,
> +			unsigned long flags,
> +			unsigned long page_shift);
> +
> +	/* initiate the transition of a VM to secure VM */
> +	unsigned long (*kvmppc_svm_init_start)(struct kvm *kvm);
> +
> +	/* finalize the transition of a secure VM */
> +	unsigned long (*kvmppc_svm_init_done)(struct kvm *kvm);
> +
> +	/* share the page on page fault */
> +	int (*kvmppc_svm_page_share)(struct kvm *kvm, unsigned long gfn);
> +
> +	/* abort the transition to a secure VM */
> +	unsigned long (*kvmppc_svm_init_abort)(struct kvm *kvm);
> +
> +	/* add a memory slot */
> +	int (*kvmppc_svm_memslot_create)(struct kvm *kvm,
> +		const struct kvm_memory_slot *new);
> +
> +	/* free a memory slot */
> +	void (*kvmppc_svm_memslot_delete)(struct kvm *kvm,
> +		const struct kvm_memory_slot *old);
> +
> +	/* drop pages allocated to the secure VM */
> +	void (*kvmppc_svm_drop_pages)(const struct kvm_memory_slot *free,
> +			     struct kvm *kvm, bool skip_page_out);
> +};

Since the structure has kvmppc_ prefix, may be you can drop
the same from its members to make the fields smaller?

> +
> +extern const struct kvmppc_hmm_backend *kvmppc_svm_backend;
> +
> +static inline int kvmppc_svm_page_share(struct kvm *kvm, unsigned long gfn)
> +{
> +	if (!kvmppc_svm_backend)
> +		return -ENODEV;
> +
> +	return kvmppc_svm_backend->kvmppc_svm_page_share(kvm,
> +				gfn);
> +}
> +
> +static inline void kvmppc_svm_drop_pages(const struct kvm_memory_slot *memslot,
> +			struct kvm *kvm, bool skip_page_out)
> +{
> +	if (!kvmppc_svm_backend)
> +		return;
> +
> +	kvmppc_svm_backend->kvmppc_svm_drop_pages(memslot,
> +			kvm, skip_page_out);
> +}
> +
> +static inline int kvmppc_svm_page_in(struct kvm *kvm,
> +			unsigned long gpa,
> +			unsigned long flags,
> +			unsigned long page_shift)
> +{
> +	if (!kvmppc_svm_backend)
> +		return -ENODEV;
> +
> +	return kvmppc_svm_backend->kvmppc_svm_page_in(kvm,
> +			gpa, flags, page_shift);
> +}
> +
> +static inline int kvmppc_svm_page_out(struct kvm *kvm,
> +			unsigned long gpa,
> +			unsigned long flags,
> +			unsigned long page_shift)
> +{
> +	if (!kvmppc_svm_backend)
> +		return -ENODEV;
> +
> +	return kvmppc_svm_backend->kvmppc_svm_page_out(kvm,
> +			gpa, flags, page_shift);
> +}
> +
> +static inline int kvmppc_svm_init_start(struct kvm *kvm)
> +{
> +	if (!kvmppc_svm_backend)
> +		return -ENODEV;
> +
> +	return kvmppc_svm_backend->kvmppc_svm_init_start(kvm);
> +}
> +
> +static inline int kvmppc_svm_init_done(struct kvm *kvm)
> +{
> +	if (!kvmppc_svm_backend)
> +		return -ENODEV;
> +
> +	return kvmppc_svm_backend->kvmppc_svm_init_done(kvm);
> +}
> +
> +static inline int kvmppc_svm_init_abort(struct kvm *kvm)
> +{
> +	if (!kvmppc_svm_backend)
> +		return -ENODEV;
> +
> +	return kvmppc_svm_backend->kvmppc_svm_init_abort(kvm);
> +}
> +
> +static inline void kvmppc_svm_memslot_create(struct kvm *kvm,
> +		const struct kvm_memory_slot *memslot)
> +{
> +	if (!kvmppc_svm_backend)
> +		return;
> +
> +	kvmppc_svm_backend->kvmppc_svm_memslot_create(kvm,
> +			memslot);
> +}
> +
> +static inline void kvmppc_svm_memslot_delete(struct kvm *kvm,
> +		const struct kvm_memory_slot *memslot)
> +{
> +	if (!kvmppc_svm_backend)
> +		return;
> +
> +	kvmppc_svm_backend->kvmppc_svm_memslot_delete(kvm,
> +			memslot);
> +}
> +
> +static inline int kvmppc_secmem_init(void)
> +{
> +#ifdef CONFIG_PPC_UV
> +	extern const struct kvmppc_hmm_backend kvmppc_uvmem_backend;
> +
> +	kvmppc_svm_backend = NULL;
> +	if (kvmhv_on_pseries()) {
> +		/* @TODO add the protected memory backend */
> +		return 0;
> +	}
> +
> +	kvmppc_svm_backend = &kvmppc_uvmem_backend;
> +
> +	if (!kvmppc_svm_backend->kvmppc_secmem_init) {

You have a function named kvmppc_secmem_init() and the field
named the same, can be confusing.

> +		pr_err("KVM-HV: kvmppc_svm_backend has no %s\n", __func__);
> +		goto err;
> +	}
> +	if (!kvmppc_svm_backend->kvmppc_secmem_free) {
> +		pr_err("KVM-HV: kvmppc_svm_backend has no kvmppc_secmem_free()\n");
> +		goto err;
> +	}
> +	if (!kvmppc_svm_backend->kvmppc_secmem_available) {
> +		pr_err("KVM-HV: kvmppc_svm_backend has no kvmppc_secmem_available()\n");
> +		goto err;
> +	}
> +	if (!kvmppc_svm_backend->kvmppc_svm_page_in) {
> +		pr_err("KVM-HV: kvmppc_svm_backend has no kvmppc_svm_page_in()\n");
> +		goto err;
> +	}
> +	if (!kvmppc_svm_backend->kvmppc_svm_page_out) {
> +		pr_err("KVM-HV: kvmppc_svm_backend has no kvmppc_svm_page_out()\n");
> +		goto err;
> +	}
> +	if (!kvmppc_svm_backend->kvmppc_svm_init_start) {
> +		pr_err("KVM-HV: kvmppc_svm_backend has no kvmppc_svm_init_start()\n");
> +		goto err;
> +	}
> +	if (!kvmppc_svm_backend->kvmppc_svm_init_done) {
> +		pr_err("KVM-HV: kvmppc_svm_backend has no kvmppc_svm_init_done()\n");
> +		goto err;
> +	}
> +	if (!kvmppc_svm_backend->kvmppc_svm_page_share) {
> +		pr_err("KVM-HV: kvmppc_svm_backend has no kvmppc_svm_page_share()\n");
> +		goto err;
> +	}
> +	if (!kvmppc_svm_backend->kvmppc_svm_init_abort) {
> +		pr_err("KVM-HV: kvmppc_svm_backend has no kvmppc_svm_init_abort()\n");
> +		goto err;
> +	}
> +	if (!kvmppc_svm_backend->kvmppc_svm_memslot_create) {
> +		pr_err("KVM-HV: kvmppc_svm_backend has no kvmppc_svm_memslot_create()\n");
> +		goto err;
> +	}
> +	if (!kvmppc_svm_backend->kvmppc_svm_memslot_delete) {
> +		pr_err("KVM-HV: kvmppc_svm_backend has no kvmppc_svm_memslot_delete()\n");
> +		goto err;
> +	}
> +	if (!kvmppc_svm_backend->kvmppc_svm_drop_pages) {
> +		pr_err("KVM-HV: kvmppc_svm_backend has no kvmppc_svm_drop_pages()\n");
> +		goto err;
> +	}

Do you really need to check each and every callback like above?
If so, may be the check can be optimized?

Regards,
Bharata.