> A secure guest will share some of its pages with hypervisor (Eg. virtio
> bounce buffers etc). Support sharing of pages between hypervisor and
> ultravisor.
>
> Once a secure page is converted to shared page, the device page is
> unmapped from the HV side page tables.
>
> Signed-off-by: Bharata B Rao <bharata@xxxxxxxxxxxxx>
> ---
> arch/powerpc/include/asm/hvcall.h | 3 ++
> arch/powerpc/kvm/book3s_hv_devm.c | 70 +++++++++++++++++++++++++++++--
> 2 files changed, 69 insertions(+), 4 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/hvcall.h b/arch/powerpc/include/asm/hvcall.h
> index 2f6b952deb0f..05b8536f6653 100644
> --- a/arch/powerpc/include/asm/hvcall.h
> +++ b/arch/powerpc/include/asm/hvcall.h
> @@ -337,6 +337,9 @@
> #define H_TLB_INVALIDATE 0xF808
> #define H_COPY_TOFROM_GUEST 0xF80C
>
> +/* Flags for H_SVM_PAGE_IN */
> +#define H_PAGE_IN_SHARED 0x1
> +
> /* Platform-specific hcalls used by the Ultravisor */
> #define H_SVM_PAGE_IN 0xEF00
> #define H_SVM_PAGE_OUT 0xEF04
> diff --git a/arch/powerpc/kvm/book3s_hv_devm.c b/arch/powerpc/kvm/book3s_hv_devm.c
> index 13722f27fa7d..6a3229b78fed 100644
> --- a/arch/powerpc/kvm/book3s_hv_devm.c
> +++ b/arch/powerpc/kvm/book3s_hv_devm.c
> @@ -46,6 +46,7 @@ struct kvmppc_devm_page_pvt {
> unsigned long *rmap;
> unsigned int lpid;
> unsigned long gpa;
> + bool skip_page_out;
> };
>
> /*
> @@ -139,6 +140,54 @@ kvmppc_devm_migrate_alloc_and_copy(struct migrate_vma *mig,
> return 0;
> }
>
> +/*
> + * Shares the page with HV, thus making it a normal page.
> + *
> + * - If the page is already secure, then provision a new page and share
> + * - If the page is a normal page, share the existing page
> + *
> + * In the former case, uses the dev_pagemap_ops migrate_to_ram handler
> + * to unmap the device page from QEMU's page tables.
> + */
> +static unsigned long
> +kvmppc_share_page(struct kvm *kvm, unsigned long gpa, unsigned long page_shift)
> +{
> +
> + int ret = H_PARAMETER;
> + struct page *devm_page;
> + struct kvmppc_devm_page_pvt *pvt;
> + unsigned long pfn;
> + unsigned long *rmap;
> + struct kvm_memory_slot *slot;
> + unsigned long gfn = gpa >> page_shift;
> + int srcu_idx;
> +
> + srcu_idx = srcu_read_lock(&kvm->srcu);
> + slot = gfn_to_memslot(kvm, gfn);
> + if (!slot)
> + goto out;
> +
> + rmap = &slot->arch.rmap[gfn - slot->base_gfn];
> + if (kvmppc_rmap_is_devm_pfn(*rmap)) {
> + devm_page = pfn_to_page(*rmap & ~KVMPPC_RMAP_DEVM_PFN);
> + pvt = (struct kvmppc_devm_page_pvt *)
> + devm_page->zone_device_data;
> + pvt->skip_page_out = true;
> + }
> +
> + pfn = gfn_to_pfn(kvm, gpa >> page_shift);
Use 'gfn'?
> + if (is_error_noslot_pfn(pfn))
> + goto out;
> +
> + ret = uv_page_in(kvm->arch.lpid, pfn << page_shift, gpa, 0, page_shift);
> + if (ret == U_SUCCESS)
> + ret = H_SUCCESS;
> + kvm_release_pfn_clean(pfn);
Nit: Blank line?
> +out:
> + srcu_read_unlock(&kvm->srcu, srcu_idx);
> + return ret;
> +}
> +
> /*
> * Move page from normal memory to secure memory.
> */
> @@ -159,9 +208,12 @@ kvmppc_h_svm_page_in(struct kvm *kvm, unsigned long gpa,
> if (page_shift != PAGE_SHIFT)
> return H_P3;
>
> - if (flags)
> + if (flags & ~H_PAGE_IN_SHARED)
> return H_P2;
>
> + if (flags & H_PAGE_IN_SHARED)
> + return kvmppc_share_page(kvm, gpa, page_shift);
> +
> ret = H_PARAMETER;
> down_read(&kvm->mm->mmap_sem);
> srcu_idx = srcu_read_lock(&kvm->srcu);
> @@ -211,7 +263,7 @@ kvmppc_devm_fault_migrate_alloc_and_copy(struct migrate_vma *mig,
> struct page *dpage, *spage;
> struct kvmppc_devm_page_pvt *pvt;
> unsigned long pfn;
> - int ret;
> + int ret = U_SUCCESS;
>
> spage = migrate_pfn_to_page(*mig->src);
> if (!spage || !(*mig->src & MIGRATE_PFN_MIGRATE))
> @@ -226,8 +278,18 @@ kvmppc_devm_fault_migrate_alloc_and_copy(struct migrate_vma *mig,
> pvt = spage->zone_device_data;
>
> pfn = page_to_pfn(dpage);
> - ret = uv_page_out(pvt->lpid, pfn << page_shift, pvt->gpa, 0,
> - page_shift);
> +
> + /*
> + * This same function is used in two cases:
Nit: s/same//
> + * - When HV touches a secure page, for which we do page-out
Better to qualify page-out with "uv page-out"? its kind of counterintuitive
to do a page-out on a fault!
> + * - When a secure page is converted to shared page, we touch
> + * the page to essentially unmap the device page. In this
> + * case we skip page-out.
> + */
> + if (!pvt->skip_page_out)
> + ret = uv_page_out(pvt->lpid, pfn << page_shift, pvt->gpa, 0,
> + page_shift);
> +
> if (ret == U_SUCCESS)
> *mig->dst = migrate_pfn(pfn) | MIGRATE_PFN_LOCKED;
> else {
> --
> 2.21.0
