[Xen-devel] [RFC 22/23] xen/privcmd: Add support for Linux 64KB page granularity
From: David Vrabel <hidden>
Date: 2015-05-19 15:40:18
Also in:
lkml
On 14/05/15 18:01, Julien Grall wrote:
The hypercall interface (as well as the toolstack) is always using 4KB page granularity. When the toolstack is asking for mapping a series of guest PFN in a batch, it expects to have the page map contiguously in its virtual memory. When Linux is using 64KB page granularity, the privcmd driver will have to map multiple Xen PFN in a single Linux page. Note that this solution works on page granularity which is a multiple of 4KB.
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quoted hunk ↗ jump to hunk
--- a/drivers/xen/xlate_mmu.c +++ b/drivers/xen/xlate_mmu.c@@ -63,6 +63,7 @@ static int map_foreign_page(unsigned long lpfn, unsigned long fgmfn, struct remap_data { xen_pfn_t *fgmfn; /* foreign domain's gmfn */ + xen_pfn_t *egmfn; /* end foreign domain's gmfn */
I don't know what you mean by "end foreign domain".
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pgprot_t prot; domid_t domid; struct vm_area_struct *vma;@@ -78,17 +79,23 @@ static int remap_pte_fn(pte_t *ptep, pgtable_t token, unsigned long addr, { struct remap_data *info = data; struct page *page = info->pages[info->index++]; - unsigned long pfn = page_to_pfn(page); - pte_t pte = pte_mkspecial(pfn_pte(pfn, info->prot)); + unsigned long pfn = xen_page_to_pfn(page); + pte_t pte = pte_mkspecial(pfn_pte(page_to_pfn(page), info->prot)); int rc; - - rc = map_foreign_page(pfn, *info->fgmfn, info->domid); - *info->err_ptr++ = rc; - if (!rc) { - set_pte_at(info->vma->vm_mm, addr, ptep, pte); - info->mapped++; + uint32_t i; + + for (i = 0; i < XEN_PFN_PER_PAGE; i++) { + if (info->fgmfn == info->egmfn) + break; + + rc = map_foreign_page(pfn++, *info->fgmfn, info->domid); + *info->err_ptr++ = rc; + if (!rc) { + set_pte_at(info->vma->vm_mm, addr, ptep, pte); + info->mapped++; + } + info->fgmfn++;
This doesn't make any sense to me. Don't you need to gather the foreign GFNs into batches of PAGE_SIZE / XEN_PAGE_SIZE and map these all at once into a 64 KiB page? I don't see how you can have a set_pte_at() for each foreign GFN. David