>>> On 28.01.16 at 21:58, <tlengyel@novetta.com> wrote:
> --- a/xen/arch/x86/mm/p2m.c
> +++ b/xen/arch/x86/mm/p2m.c
> @@ -1777,14 +1777,57 @@ bool_t p2m_mem_access_check(paddr_t gpa, unsigned long gla,
> return (p2ma == p2m_access_n2rwx);
> }
>
> +static int p2m_set_altp2m_mem_access(struct domain *d, struct p2m_domain *hp2m,
> + struct p2m_domain *ap2m, p2m_access_t a,
> + unsigned long gfn)
I think new functions would better not use "unsigned long" for frame
numbers.
With there not being any involved error handling here, I don't think
> +{
> + mfn_t mfn;
> + p2m_type_t t;
> + p2m_access_t old_a;
> + unsigned int page_order;
> + int rc;
> +
> + mfn = ap2m->get_entry(ap2m, gfn, &t, &old_a, 0, NULL, NULL);
> +
> + /* Check host p2m if no valid entry in alternate */
> + if ( !mfn_valid(mfn) )
> + {
> + mfn = hp2m->get_entry(hp2m, gfn, &t, &old_a,
> + P2M_ALLOC | P2M_UNSHARE, &page_order, NULL);
> +
> + rc = -ESRCH;
> + if ( !mfn_valid(mfn) || t != p2m_ram_rw )
> + goto out;
> +
> + /* If this is a superpage, copy that first */
> + if ( page_order != PAGE_ORDER_4K )
> + {
> + unsigned long mask = ~((1UL << page_order) - 1);
> + gfn_t gfn2 = _gfn(gfn & mask);
> + mfn_t mfn2 = _mfn(mfn_x(mfn) & mask);
> +
> + rc = ap2m->set_entry(ap2m, gfn_x(gfn2), mfn2, page_order, t, old_a, 1);
> + if ( rc )
> + goto out;
> + }
> + }
> +
> + rc = ap2m->set_entry(ap2m, gfn, mfn, PAGE_ORDER_4K, t, a,
> + (current->domain != d));
> +
> + out:
> + return rc;
> +}
using a label and goto is warranted here. But I'll leave the ultimate
decision to George, of course.
> --- a/xen/include/public/memory.h
> +++ b/xen/include/public/memory.h
> @@ -423,11 +423,14 @@ struct xen_mem_access_op {
> /* xenmem_access_t */
> uint8_t access;
> domid_t domid;
> + uint16_t altp2m_idx;
> + uint16_t _pad;
> /*
> * Number of pages for set op
> * Ignored on setting default access and other ops
> */
> uint32_t nr;
> + uint32_t _pad2;
Repeating what I had said on v1: So this is a tools only interface,
yes. But it's not versioned (other than e.g. domctl and sysctl), so
altering the interface structure is at least fragile.