[PATCH 1/8] IOMMU/x86: drop locking from quarantine_init() hooks

[Jan Beulich <jbeulich@xxxxxxxx>]

Prior extension of these functions to enable per-device quarantine page
tables already didn't add more locking there, but merely left in place
what had been there before. But really locking is unnecessary here:
We're running with pcidevs_lock held (i.e. multiple invocations of the
same function [or their teardown equivalents] are impossible, and hence
there are no "local" races), while all consuming of the data being
populated here can't race anyway due to happening sequentially
afterwards. See also the comment in struct arch_pci_dev.

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

--- a/xen/drivers/passthrough/amd/iommu_map.c
+++ b/xen/drivers/passthrough/amd/iommu_map.c
@@ -699,15 +699,11 @@ int cf_check amd_iommu_quarantine_init(s
         union amd_iommu_pte *root;
         struct page_info *pgs[IOMMU_MAX_PT_LEVELS] = {};
 
-        spin_lock(&hd->arch.mapping_lock);
-
         root = __map_domain_page(pdev->arch.amd.root_table);
         rc = fill_qpt(root, level - 1, pgs);
         unmap_domain_page(root);
 
         pdev->arch.leaf_mfn = page_to_mfn(pgs[0]);
-
-        spin_unlock(&hd->arch.mapping_lock);
     }
 
     page_list_move(&pdev->arch.pgtables_list, &hd->arch.pgtables.list);
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -3054,15 +3054,11 @@ static int cf_check intel_iommu_quaranti
         struct dma_pte *root;
         struct page_info *pgs[6] = {};
 
-        spin_lock(&hd->arch.mapping_lock);
-
         root = map_vtd_domain_page(pdev->arch.vtd.pgd_maddr);
         rc = fill_qpt(root, level - 1, pgs);
         unmap_vtd_domain_page(root);
 
         pdev->arch.leaf_mfn = page_to_mfn(pgs[0]);
-
-        spin_unlock(&hd->arch.mapping_lock);
     }
 
     page_list_move(&pdev->arch.pgtables_list, &hd->arch.pgtables.list);