[PATCH v2 05/12] IOMMU: rename and re-type ats_enabled

[Jan Beulich <jbeulich@suse.com>]

Make the variable a tristate, with (as done elsewhere) a negative value
meaning "default". Since all use sites need looking at, also rename it
to match our usual "opt_*" pattern. While touching it, also move it to
.data.ro_after_init.

The only place it retains boolean nature is pci_ats_device(), for now.

In AMD code re-order conditionals to have the config space accesses
after (cheaper) flag checks.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
---
In domain_context_mapping_one() I'm a little puzzled that translation
type is selected based on only IOMMU and global properties, i.e. not
taking the device itself into account.
---
v2: Re-base over new earlier patches.

--- a/xen/drivers/passthrough/amd/iommu_cmd.c
+++ b/xen/drivers/passthrough/amd/iommu_cmd.c
@@ -282,7 +282,7 @@ void amd_iommu_flush_iotlb(u8 devfn, con
     struct amd_iommu *iommu;
     unsigned int req_id, queueid, maxpend;
 
-    if ( !ats_enabled )
+    if ( opt_ats <= 0 )
         return;
 
     if ( !pci_ats_enabled(pdev->seg, pdev->bus, pdev->devfn) )
@@ -340,7 +340,7 @@ static void _amd_iommu_flush_pages(struc
         flush_command_buffer(iommu, 0);
     }
 
-    if ( ats_enabled )
+    if ( opt_ats > 0 )
     {
         amd_iommu_flush_all_iotlbs(d, daddr, order);
 
--- a/xen/drivers/passthrough/amd/pci_amd_iommu.c
+++ b/xen/drivers/passthrough/amd/pci_amd_iommu.c
@@ -119,7 +119,7 @@ static bool use_ats(
     const struct amd_iommu *iommu,
     const struct ivrs_mappings *ivrs_dev)
 {
-    return !ivrs_dev->block_ats &&
+    return opt_ats > 0 && !ivrs_dev->block_ats &&
            iommu_has_cap(iommu, PCI_CAP_IOTLB_SHIFT) &&
            pci_ats_device(iommu->seg, pdev->bus, pdev->devfn);
 }
@@ -196,7 +196,7 @@ static int __must_check amd_iommu_setup_
         dte->sys_mgt = MASK_EXTR(ivrs_dev->device_flags, ACPI_IVHD_SYSTEM_MGMT);
 
         if ( use_ats(pdev, iommu, ivrs_dev) )
-            dte->i = ats_enabled;
+            dte->i = true;
 
         spin_unlock_irqrestore(&iommu->lock, flags);
 
@@ -257,7 +257,7 @@ static int __must_check amd_iommu_setup_
                                          ACPI_IVHD_SYSTEM_MGMT));
 
         if ( use_ats(pdev, iommu, ivrs_dev) )
-            ASSERT(dte->i == ats_enabled);
+            ASSERT(dte->i);
 
         spin_unlock_irqrestore(&iommu->lock, flags);
 
--- a/xen/drivers/passthrough/ats.c
+++ b/xen/drivers/passthrough/ats.c
@@ -18,8 +18,8 @@
 #include <xen/pci_regs.h>
 #include "ats.h"
 
-bool __read_mostly ats_enabled;
-boolean_param("ats", ats_enabled);
+int8_t __ro_after_init opt_ats = -1;
+boolean_param("ats", opt_ats);
 
 int enable_ats_device(struct pci_dev *pdev, struct list_head *ats_list)
 {
--- a/xen/drivers/passthrough/ats.h
+++ b/xen/drivers/passthrough/ats.h
@@ -22,7 +22,7 @@
 #define ATS_QUEUE_DEPTH_MASK     0x1f
 #define ATS_ENABLE               (1<<15)
 
-extern bool ats_enabled;
+extern int8_t opt_ats;
 
 int enable_ats_device(struct pci_dev *pdev, struct list_head *ats_list);
 void disable_ats_device(struct pci_dev *pdev);
@@ -43,7 +43,7 @@ static inline int pci_ats_enabled(int se
 
 static inline int pci_ats_device(int seg, int bus, int devfn)
 {
-    if ( !ats_enabled )
+    if ( !opt_ats )
         return 0;
 
     return pci_find_ext_capability(PCI_SBDF(seg, bus, devfn),
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -1543,7 +1543,7 @@ int domain_context_mapping_one(
         }
 
         context_set_address_root(lctxt, root);
-        if ( ats_enabled && ecap_dev_iotlb(iommu->ecap) )
+        if ( opt_ats > 0 && ecap_dev_iotlb(iommu->ecap) )
             context_set_translation_type(lctxt, CONTEXT_TT_DEV_IOTLB);
         else
             context_set_translation_type(lctxt, CONTEXT_TT_MULTI_LEVEL);
--- a/xen/drivers/passthrough/vtd/x86/ats.c
+++ b/xen/drivers/passthrough/vtd/x86/ats.c
@@ -46,7 +46,7 @@ int ats_device(const struct pci_dev *pde
     struct acpi_drhd_unit *ats_drhd;
     unsigned int pos, expfl = 0;
 
-    if ( !ats_enabled || !iommu_qinval )
+    if ( opt_ats <= 0 || !iommu_qinval )
         return 0;
 
     if ( !ecap_queued_inval(drhd->iommu->ecap) ||