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SubjectRE: [PATCH v2] xen/privcmd: add IOCTL_PRIVCMD_MMAP_RESOURCE
Date
> -----Original Message-----
> From: Boris Ostrovsky [mailto:boris.ostrovsky@oracle.com]
> Sent: 05 April 2018 23:34
> To: Paul Durrant <Paul.Durrant@citrix.com>; x86@kernel.org; xen-
> devel@lists.xenproject.org; linux-kernel@vger.kernel.org
> Cc: Juergen Gross <jgross@suse.com>; Thomas Gleixner
> <tglx@linutronix.de>; Ingo Molnar <mingo@redhat.com>
> Subject: Re: [PATCH v2] xen/privcmd: add
> IOCTL_PRIVCMD_MMAP_RESOURCE
>
> On 04/05/2018 11:42 AM, Paul Durrant wrote:
> > My recent Xen patch series introduces a new HYPERVISOR_memory_op to
> > support direct priv-mapping of certain guest resources (such as ioreq
> > pages, used by emulators) by a tools domain, rather than having to access
> > such resources via the guest P2M.
> >
> > This patch adds the necessary infrastructure to the privcmd driver and
> > Xen MMU code to support direct resource mapping.
> >
> > NOTE: The adjustment in the MMU code is partially cosmetic. Xen will now
> > allow a PV tools domain to map guest pages either by GFN or MFN, thus
> > the term 'mfn' has been swapped for 'pfn' in the lower layers of the
> > remap code.
> >
> > Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
> > ---
> > Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> > Cc: Juergen Gross <jgross@suse.com>
> > Cc: Thomas Gleixner <tglx@linutronix.de>
> > Cc: Ingo Molnar <mingo@redhat.com>
> >
> > v2:
> > - Fix bug when mapping multiple pages of a resource
>
>
> Only a few nits below.
>
> > ---
> > arch/x86/xen/mmu.c | 50 +++++++++++-----
> > drivers/xen/privcmd.c | 130
> +++++++++++++++++++++++++++++++++++++++++
> > include/uapi/xen/privcmd.h | 11 ++++
> > include/xen/interface/memory.h | 66 +++++++++++++++++++++
> > include/xen/interface/xen.h | 7 ++-
> > include/xen/xen-ops.h | 24 +++++++-
> > 6 files changed, 270 insertions(+), 18 deletions(-)
> >
> > diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
> > index d33e7dbe3129..8453d7be415c 100644
> > --- a/arch/x86/xen/mmu.c
> > +++ b/arch/x86/xen/mmu.c
> > @@ -65,37 +65,42 @@ static void xen_flush_tlb_all(void)
> > #define REMAP_BATCH_SIZE 16
> >
> > struct remap_data {
> > - xen_pfn_t *mfn;
> > + xen_pfn_t *pfn;
> > bool contiguous;
> > + bool no_translate;
> > pgprot_t prot;
> > struct mmu_update *mmu_update;
> > };
> >
> > -static int remap_area_mfn_pte_fn(pte_t *ptep, pgtable_t token,
> > +static int remap_area_pfn_pte_fn(pte_t *ptep, pgtable_t token,
> > unsigned long addr, void *data)
> > {
> > struct remap_data *rmd = data;
> > - pte_t pte = pte_mkspecial(mfn_pte(*rmd->mfn, rmd->prot));
> > + pte_t pte = pte_mkspecial(mfn_pte(*rmd->pfn, rmd->prot));
> >
> > /* If we have a contiguous range, just update the mfn itself,
> > else update pointer to be "next mfn". */
>
> This probably also needs to be updated (and while at it, comment style
> fixed)
>

Ok.

> > if (rmd->contiguous)
> > - (*rmd->mfn)++;
> > + (*rmd->pfn)++;
> > else
> > - rmd->mfn++;
> > + rmd->pfn++;
> >
> > - rmd->mmu_update->ptr = virt_to_machine(ptep).maddr |
> MMU_NORMAL_PT_UPDATE;
> > + rmd->mmu_update->ptr = virt_to_machine(ptep).maddr;
> > + rmd->mmu_update->ptr |= rmd->no_translate ?
> > + MMU_PT_UPDATE_NO_TRANSLATE :
> > + MMU_NORMAL_PT_UPDATE;
> > rmd->mmu_update->val = pte_val_ma(pte);
> > rmd->mmu_update++;
> >
> > return 0;
> > }
> >
> > -static int do_remap_gfn(struct vm_area_struct *vma,
> > +static int do_remap_pfn(struct vm_area_struct *vma,
> > unsigned long addr,
> > - xen_pfn_t *gfn, int nr,
> > + xen_pfn_t *pfn, int nr,
> > int *err_ptr, pgprot_t prot,
> > - unsigned domid,
> > + unsigned int domid,
> > + bool no_translate,
> > struct page **pages)
> > {
> > int err = 0;
> > @@ -106,11 +111,12 @@ static int do_remap_gfn(struct vm_area_struct
> *vma,
> >
> > BUG_ON(!((vma->vm_flags & (VM_PFNMAP | VM_IO)) ==
> (VM_PFNMAP | VM_IO)));
> >
> > - rmd.mfn = gfn;
> > + rmd.pfn = pfn;
> > rmd.prot = prot;
> > /* We use the err_ptr to indicate if there we are doing a contiguous
> > * mapping or a discontigious mapping. */
>
> Style.
>

I'm not modifying this comment but I'll fix it.

> > rmd.contiguous = !err_ptr;
> > + rmd.no_translate = no_translate;
> >
> > while (nr) {
> > int index = 0;
> > @@ -121,7 +127,7 @@ static int do_remap_gfn(struct vm_area_struct
> *vma,
> >
> > rmd.mmu_update = mmu_update;
> > err = apply_to_page_range(vma->vm_mm, addr, range,
> > - remap_area_mfn_pte_fn, &rmd);
> > + remap_area_pfn_pte_fn, &rmd);
> > if (err)
> > goto out;
> >
> > @@ -175,7 +181,8 @@ int xen_remap_domain_gfn_range(struct
> vm_area_struct *vma,
> > if (xen_feature(XENFEAT_auto_translated_physmap))
> > return -EOPNOTSUPP;
> >
> > - return do_remap_gfn(vma, addr, &gfn, nr, NULL, prot, domid,
> pages);
> > + return do_remap_pfn(vma, addr, &gfn, nr, NULL, prot, domid, false,
> > + pages);
> > }
> > EXPORT_SYMBOL_GPL(xen_remap_domain_gfn_range);
> >
> > @@ -183,7 +190,7 @@ int xen_remap_domain_gfn_array(struct
> vm_area_struct *vma,
> > unsigned long addr,
> > xen_pfn_t *gfn, int nr,
> > int *err_ptr, pgprot_t prot,
> > - unsigned domid, struct page **pages)
> > + unsigned int domid, struct page **pages)
>
> Is this really necessary? And if it is, then why are other routines
> (e.g. xen_remap_domain_gfn_range() above) not updated as well?
>

Ok. It's style fix-up but I can leave it.

> > {
> > if (xen_feature(XENFEAT_auto_translated_physmap))
> > return xen_xlate_remap_gfn_array(vma, addr, gfn, nr,
> err_ptr,
> > @@ -194,10 +201,25 @@ int xen_remap_domain_gfn_array(struct
> vm_area_struct *vma,
> > * cause of "wrong memory was mapped in".
> > */
> > BUG_ON(err_ptr == NULL);
> > - return do_remap_gfn(vma, addr, gfn, nr, err_ptr, prot, domid,
> pages);
> > + return do_remap_pfn(vma, addr, gfn, nr, err_ptr, prot, domid,
> > + false, pages);
> > }
> > EXPORT_SYMBOL_GPL(xen_remap_domain_gfn_array);
> >
> > +int xen_remap_domain_mfn_array(struct vm_area_struct *vma,
> > + unsigned long addr,
> > + xen_pfn_t *mfn, int nr,
> > + int *err_ptr, pgprot_t prot,
> > + unsigned int domid, struct page **pages)
> > +{
> > + if (xen_feature(XENFEAT_auto_translated_physmap))
> > + return -EOPNOTSUPP;
> > +
> > + return do_remap_pfn(vma, addr, mfn, nr, err_ptr, prot, domid,
> > + true, pages);
> > +}
> > +EXPORT_SYMBOL_GPL(xen_remap_domain_mfn_array);
> > +
> > /* Returns: 0 success */
> > int xen_unmap_domain_gfn_range(struct vm_area_struct *vma,
> > int nr, struct page **pages)
> > diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
> > index 1c909183c42a..cca809a204ab 100644
> > --- a/drivers/xen/privcmd.c
> > +++ b/drivers/xen/privcmd.c
> > @@ -33,6 +33,7 @@
> > #include <xen/xen.h>
> > #include <xen/privcmd.h>
> > #include <xen/interface/xen.h>
> > +#include <xen/interface/memory.h>
> > #include <xen/interface/hvm/dm_op.h>
> > #include <xen/features.h>
> > #include <xen/page.h>
> > @@ -722,6 +723,131 @@ static long privcmd_ioctl_restrict(struct file *file,
> void __user *udata)
> > return 0;
> > }
> >
> > +struct remap_pfn {
> > + struct mm_struct *mm;
> > + struct page **pages;
> > + pgprot_t prot;
> > + unsigned long i;
> > +};
> > +
> > +static int remap_pfn(pte_t *ptep, pgtable_t token, unsigned long addr,
>
>
> Maybe remap_pfn_fn (to avoid name shadowing)?
>

Ok.

>
> > + void *data)
> > +{
> > + struct remap_pfn *r = data;
> > + struct page *page = r->pages[r->i];
> > + pte_t pte = pte_mkspecial(pfn_pte(page_to_pfn(page), r->prot));
> > +
> > + set_pte_at(r->mm, addr, ptep, pte);
> > + r->i++;
> > +
> > + return 0;
> > +}
> > +
> > +static long privcmd_ioctl_mmap_resource(struct file *file, void __user
> *udata)
> > +{
> > + struct privcmd_data *data = file->private_data;
> > + struct mm_struct *mm = current->mm;
> > + struct vm_area_struct *vma;
> > + struct privcmd_mmap_resource kdata;
> > + xen_pfn_t *pfns = NULL;
> > + struct xen_mem_acquire_resource xdata;
> > + int rc;
> > +
> > + if (copy_from_user(&kdata, udata, sizeof(kdata)))
> > + return -EFAULT;
> > +
> > + /* If restriction is in place, check the domid matches */
> > + if (data->domid != DOMID_INVALID && data->domid != kdata.dom)
> > + return -EPERM;
> > +
> > + down_write(&mm->mmap_sem);
> > +
> > + vma = find_vma(mm, kdata.addr);
> > + if (!vma || vma->vm_ops != &privcmd_vm_ops) {
> > + rc = -EINVAL;
> > + goto out;
> > + }
> > +
> > + pfns = kcalloc(kdata.num, sizeof(*pfns), GFP_KERNEL);
> > + if (!pfns) {
> > + rc = -ENOMEM;
> > + goto out;
> > + }
> > +
> > + if (xen_feature(XENFEAT_auto_translated_physmap)) {
> > + struct page **pages;
> > + unsigned int i;
> > +
> > + rc = alloc_empty_pages(vma, kdata.num);
> > + if (rc < 0)
> > + goto out;
> > +
> > + pages = vma->vm_private_data;
> > + for (i = 0; i < kdata.num; i++) {
> > + pfns[i] = page_to_pfn(pages[i]);
> > + pr_info("pfn[%u] = %p\n", i, (void *)pfns[i]);
> > + }
> > + } else
> > + vma->vm_private_data = PRIV_VMA_LOCKED;
> > +
> > + memset(&xdata, 0, sizeof(xdata));
> > + xdata.domid = kdata.dom;
> > + xdata.type = kdata.type;
> > + xdata.id = kdata.id;
> > + xdata.frame = kdata.idx;
> > + xdata.nr_frames = kdata.num;
> > + set_xen_guest_handle(xdata.frame_list, pfns);
> > +
> > + xen_preemptible_hcall_begin();
> > + rc = HYPERVISOR_memory_op(XENMEM_acquire_resource,
> &xdata);
> > + xen_preemptible_hcall_end();
> > +
> > + if (rc)
> > + goto out;
> > +
> > + if (xen_feature(XENFEAT_auto_translated_physmap)) {
> > + struct remap_pfn r = {
> > + .mm = vma->vm_mm,
> > + .pages = vma->vm_private_data,
> > + .prot = vma->vm_page_prot,
> > + };
> > +
> > + rc = apply_to_page_range(r.mm, kdata.addr,
> > + kdata.num << PAGE_SHIFT,
> > + remap_pfn, &r);
> > + } else {
> > + unsigned int domid =
> > + (xdata.flags & XENMEM_rsrc_acq_caller_owned) ?
> > + DOMID_SELF : kdata.dom;
> > + int num;
> > +
> > + num = xen_remap_domain_mfn_array(vma,
> > + kdata.addr & PAGE_MASK,
> > + pfns, kdata.num, (int *)pfns,
> > + vma->vm_page_prot,
> > + domid,
> > + vma->vm_private_data);
> > + if (num < 0)
> > + rc = num;
> > + else if (num != kdata.num) {
> > + unsigned int i;
> > +
> > + for (i = 0; i < num; i++) {
> > + rc = pfns[i];
> > + if (rc < 0)
> > + break;
> > + }
> > + } else
> > + rc = 0;
> > + }
> > +
> > +out:
> > + kfree(pfns);
> > +
> > + up_write(&mm->mmap_sem);
>
> I'd swap these two.
>

Ok.

I'll need to fix the ARM build breakage too. V2 coming shortly.

Paul

>
> -boris
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