> A secure guest will share some of its pages with hypervisor (Eg. virtio
> bounce buffers etc). Support sharing of pages between hypervisor and
> ultravisor.
A brief note about what a shared page is would help (a page belonging
to the SVM but in normal memory and with decrypted contents)? Either
here or in the function header of kvmppc_h_svm_page_in() where we
handle shared pages.
>
> Once a secure page is converted to shared page, the device page is
Maybe useful to add "the device page (representing the secure 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_uvmem.c | 65 ++++++++++++++++++++++++++++--
> 2 files changed, 65 insertions(+), 3 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/hvcall.h b/arch/powerpc/include/asm/hvcall.h
> index 2595d0144958..4e98dd992bd1 100644
> --- a/arch/powerpc/include/asm/hvcall.h
> +++ b/arch/powerpc/include/asm/hvcall.h
> @@ -342,6 +342,9 @@
> #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_uvmem.c b/arch/powerpc/kvm/book3s_hv_uvmem.c
> index a1eccb065ba9..bcecb643a730 100644
> --- a/arch/powerpc/kvm/book3s_hv_uvmem.c
> +++ b/arch/powerpc/kvm/book3s_hv_uvmem.c
> @@ -46,6 +46,7 @@ struct kvmppc_uvmem_page_pvt {
> unsigned long *rmap;
> unsigned int lpid;
> unsigned long gpa;
> + bool skip_page_out;
> };
>
> /*
> @@ -159,6 +160,53 @@ kvmppc_svm_page_in(struct vm_area_struct *vma, unsigned long start,
> return ret;
> }
>
> +/*
> + * 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 *uvmem_page;
> + struct kvmppc_uvmem_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_type(rmap) == KVMPPC_RMAP_UVMEM_PFN) {
> + uvmem_page = pfn_to_page(*rmap & ~KVMPPC_RMAP_UVMEM_PFN);
> + pvt = (struct kvmppc_uvmem_page_pvt *)
> + uvmem_page->zone_device_data;
> + pvt->skip_page_out = true;
> + }
> +
> + pfn = gfn_to_pfn(kvm, gfn);
> + if (is_error_noslot_pfn(pfn))
> + goto out;
> +
> + if (!uv_page_in(kvm->arch.lpid, pfn << page_shift, gpa, 0, page_shift))
> + ret = H_SUCCESS;
> + kvm_release_pfn_clean(pfn);
> +out:
> + srcu_read_unlock(&kvm->srcu, srcu_idx);
> + return ret;
> +}
> +
> /*
> * H_SVM_PAGE_IN: Move page from normal memory to secure memory.
Would help to mention/remind here what a shared page is.
> */
> @@ -177,9 +225,12 @@ 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;
> srcu_idx = srcu_read_lock(&kvm->srcu);
> down_read(&kvm->mm->mmap_sem);
> @@ -252,8 +303,16 @@ kvmppc_svm_page_out(struct vm_area_struct *vma, unsigned long start,
> 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 function is used in two cases:
> + * - When HV touches a secure page, for which we do UV_PAGE_OUT
> + * - 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;
> --
> 2.21.0
