xen: use _PAGE_IOMAP in ioremap to do machine mappings

In a Xen domain, ioremap operates on machine addresses, not
pseudo-physical addresses.  We use _PAGE_IOMAP to determine whether a
mapping is intended for machine addresses.

[ Impact: allow Xen domain to map real hardware ]

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 69 insertions, 2 deletions

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 914f04695ce5..a4dea9df0cc0 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -56,9 +56,11 @@
 #include <asm/xen/hypercall.h>
 #include <asm/xen/hypervisor.h>
 
+#include <xen/xen.h>
 #include <xen/page.h>
 #include <xen/interface/xen.h>
 #include <xen/interface/version.h>
+#include <xen/interface/memory.h>
 #include <xen/hvc-console.h>
 
 #include "multicalls.h"
@@ -377,6 +379,28 @@ static bool xen_page_pinned(void *ptr)
         return PagePinned(page);
 }
 
+static bool xen_iomap_pte(pte_t pte)
+{
+        return xen_initial_domain() && (pte_flags(pte) & _PAGE_IOMAP);
+}
+
+static void xen_set_iomap_pte(pte_t *ptep, pte_t pteval)
+{
+        struct multicall_space mcs;
+        struct mmu_update *u;
+
+        mcs = xen_mc_entry(sizeof(*u));
+        u = mcs.args;
+
+        /* ptep might be kmapped when using 32-bit HIGHPTE */
+        u->ptr = arbitrary_virt_to_machine(ptep).maddr;
+        u->val = pte_val_ma(pteval);
+
+        MULTI_mmu_update(mcs.mc, mcs.args, 1, NULL, DOMID_IO);
+
+        xen_mc_issue(PARAVIRT_LAZY_MMU);
+}
+
 static void xen_extend_mmu_update(const struct mmu_update *update)
 {
         struct multicall_space mcs;
@@ -453,6 +477,11 @@ void set_pte_mfn(unsigned long vaddr, unsigned long mfn, pgprot_t flags)
 void xen_set_pte_at(struct mm_struct *mm, unsigned long addr,
                     pte_t *ptep, pte_t pteval)
 {
+        if (xen_iomap_pte(pteval)) {
+                xen_set_iomap_pte(ptep, pteval);
+                goto out;
+        }
+
         ADD_STATS(set_pte_at, 1);
 //      ADD_STATS(set_pte_at_pinned, xen_page_pinned(ptep));
         ADD_STATS(set_pte_at_current, mm == current->mm);
@@ -523,8 +552,25 @@ static pteval_t pte_pfn_to_mfn(pteval_t val)
         return val;
 }
 
+static pteval_t iomap_pte(pteval_t val)
+{
+        if (val & _PAGE_PRESENT) {
+                unsigned long pfn = (val & PTE_PFN_MASK) >> PAGE_SHIFT;
+                pteval_t flags = val & PTE_FLAGS_MASK;
+
+                /* We assume the pte frame number is a MFN, so
+                   just use it as-is. */
+                val = ((pteval_t)pfn << PAGE_SHIFT) | flags;
+        }
+
+        return val;
+}
+
 pteval_t xen_pte_val(pte_t pte)
 {
+        if (xen_initial_domain() && (pte.pte & _PAGE_IOMAP))
+                return pte.pte;
+
         return pte_mfn_to_pfn(pte.pte);
 }
 PV_CALLEE_SAVE_REGS_THUNK(xen_pte_val);
@@ -537,7 +583,11 @@ PV_CALLEE_SAVE_REGS_THUNK(xen_pgd_val);
 
 pte_t xen_make_pte(pteval_t pte)
 {
-        pte = pte_pfn_to_mfn(pte);
+        if (unlikely(xen_initial_domain() && (pte & _PAGE_IOMAP)))
+                pte = iomap_pte(pte);
+        else
+                pte = pte_pfn_to_mfn(pte);
+
         return native_make_pte(pte);
 }
 PV_CALLEE_SAVE_REGS_THUNK(xen_make_pte);
@@ -593,6 +643,11 @@ void xen_set_pud(pud_t *ptr, pud_t val)
 
 void xen_set_pte(pte_t *ptep, pte_t pte)
 {
+        if (xen_iomap_pte(pte)) {
+                xen_set_iomap_pte(ptep, pte);
+                return;
+        }
+
         ADD_STATS(pte_update, 1);
 //      ADD_STATS(pte_update_pinned, xen_page_pinned(ptep));
         ADD_STATS(pte_update_batched, paravirt_get_lazy_mode() == PARAVIRT_LAZY_MMU);
@@ -609,6 +664,11 @@ void xen_set_pte(pte_t *ptep, pte_t pte)
 #ifdef CONFIG_X86_PAE
 void xen_set_pte_atomic(pte_t *ptep, pte_t pte)
 {
+        if (xen_iomap_pte(pte)) {
+                xen_set_iomap_pte(ptep, pte);
+                return;
+        }
+
         set_64bit((u64 *)ptep, native_pte_val(pte));
 }
 
@@ -1811,9 +1871,16 @@ static void xen_set_fixmap(unsigned idx, phys_addr_t phys, pgprot_t prot)
                 pte = pfn_pte(phys, prot);
                 break;
 
-        default:
+        case FIX_PARAVIRT_BOOTMAP:
+                /* This is an MFN, but it isn't an IO mapping from the
+                   IO domain */
                 pte = mfn_pte(phys, prot);
                 break;
+
+        default:
+                /* By default, set_fixmap is used for hardware mappings */
+                pte = mfn_pte(phys, __pgprot(pgprot_val(prot) | _PAGE_IOMAP));
+                break;
         }
 
         __native_set_fixmap(idx, pte);