VT-d: use ioremap()

There's no point in using the fixmap here, and it gets iommu_alloc()
in line with iommu_free(), which was already using iounmap() (thus
crashing if actually used).

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/drivers/passthrough/vtd/dmar.h
+++ b/xen/drivers/passthrough/vtd/dmar.h
@@ -127,8 +127,6 @@ do {                                    
     }                                                           \
 } while (0)
 
-void *map_to_nocache_virt(int nr_iommus, u64 maddr);
-
 int vtd_hw_check(void);
 void disable_pmr(struct iommu *iommu);
 int is_usb_device(u16 seg, u8 bus, u8 devfn);
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -1143,7 +1143,7 @@ int __init iommu_alloc(struct acpi_drhd_
     }
     iommu->intel->drhd = drhd;
 
-    iommu->reg = map_to_nocache_virt(nr_iommus, drhd->address);
+    iommu->reg = ioremap(drhd->address, PAGE_SIZE);
     iommu->index = nr_iommus++;
 
     iommu->cap = dmar_readq(iommu->reg, DMAR_CAP_REG);
--- a/xen/drivers/passthrough/vtd/x86/vtd.c
+++ b/xen/drivers/passthrough/vtd/x86/vtd.c
@@ -64,12 +64,6 @@ void flush_all_cache()
     wbinvd();
 }
 
-void *__init map_to_nocache_virt(int nr_iommus, u64 maddr)
-{
-    set_fixmap_nocache(FIX_IOMMU_REGS_BASE_0 + nr_iommus, maddr);
-    return (void *)fix_to_virt(FIX_IOMMU_REGS_BASE_0 + nr_iommus);
-}
-
 static int _hvm_dpci_isairq_eoi(struct domain *d,
                                 struct hvm_pirq_dpci *pirq_dpci, void *arg)
 {
--- a/xen/include/asm-x86/fixmap.h
+++ b/xen/include/asm-x86/fixmap.h
@@ -60,8 +60,6 @@ enum fixed_addresses {
     FIX_KEXEC_BASE_0,
     FIX_KEXEC_BASE_END = FIX_KEXEC_BASE_0 \
       + ((KEXEC_XEN_NO_PAGES >> 1) * KEXEC_IMAGE_NR) - 1,
-    FIX_IOMMU_REGS_BASE_0,
-    FIX_IOMMU_REGS_END = FIX_IOMMU_REGS_BASE_0 + MAX_IOMMUS-1,
     FIX_IOMMU_MMIO_BASE_0,
     FIX_IOMMU_MMIO_END = FIX_IOMMU_MMIO_BASE_0 + IOMMU_PAGES -1,
     FIX_TBOOT_SHARED_BASE,