[Xen-devel] [PATCH] x86: rework hypercall argument translation area setup

["Jan Beulich" <JBeulich@xxxxxxxx>]

Rather than using an order-1 Xen heap allocation, use (currently 2)
individual domain heap pages to populate space in the per-domain
mapping area.

Also fix an off-by-one mistake in is_compat_arg_xlat_range().

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

--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -642,6 +642,14 @@ void arch_domain_destroy(struct domain *
             free_domheap_page(d->arch.perdomain_l2_pg[i]);
     free_domheap_page(d->arch.perdomain_l3_pg);
 
+    if ( d->arch.arg_xlat_l1_pg )
+    {
+        for ( i = 0; i < PFN_UP(MAX_VIRT_CPUS << ARG_XLAT_VA_SHIFT); ++i )
+            if ( d->arch.arg_xlat_l1_pg[i] )
+                free_domheap_page(d->arch.arg_xlat_l1_pg[i]);
+        xfree(d->arch.arg_xlat_l1_pg);
+    }
+
     free_xenheap_page(d->shared_info);
     cleanup_domain_irq_mapping(d);
 }
--- a/xen/arch/x86/usercopy.c
+++ b/xen/arch/x86/usercopy.c
@@ -6,8 +6,8 @@
  * Copyright 2002 Andi Kleen <ak@xxxxxxx>
  */
 
-#include <xen/config.h>
 #include <xen/lib.h>
+#include <xen/sched.h>
 #include <asm/uaccess.h>
 
 unsigned long __copy_to_user_ll(void __user *to, const void *from, unsigned n)
--- a/xen/arch/x86/x86_64/mm.c
+++ b/xen/arch/x86/x86_64/mm.c
@@ -832,27 +832,93 @@ void __init zap_low_mappings(void)
                      __PAGE_HYPERVISOR);
 }
 
-void *compat_arg_xlat_virt_base(void)
-{
-    return current->arch.compat_arg_xlat;
-}
-
 int setup_compat_arg_xlat(struct vcpu *v)
 {
-    unsigned int order = get_order_from_bytes(COMPAT_ARG_XLAT_SIZE);
+    struct domain *d = v->domain;
+    struct page_info *pg;
+    unsigned int idx, i;
+    l1_pgentry_t *l1tab;
+
+    if ( !d->arch.perdomain_l2_pg[ARG_XLAT_SLOT] )
+    {
+        l3_pgentry_t *l3tab;
+
+        pg = alloc_domheap_page(NULL, MEMF_node(domain_to_node(d)));
+        if ( !pg )
+            return -ENOMEM;
+        clear_domain_page(page_to_mfn(pg));
+        d->arch.perdomain_l2_pg[ARG_XLAT_SLOT] = pg;
+
+        l3tab = __map_domain_page(d->arch.perdomain_l3_pg);
+        l3tab[l3_table_offset(ARG_XLAT_VIRT_START)] =
+            l3e_from_page(pg, __PAGE_HYPERVISOR);
+        unmap_domain_page(l3tab);
+    }
+
+    BUILD_BUG_ON((MAX_VIRT_CPUS << ARG_XLAT_VA_SHIFT) >
+                 (PERDOMAIN_SLOT_MBYTES << 20));
+
+    if ( !d->arch.arg_xlat_l1_pg )
+        d->arch.arg_xlat_l1_pg = xzalloc_array(struct page_info *,
+                                               PFN_UP(MAX_VIRT_CPUS <<
+                                                      ARG_XLAT_VA_SHIFT));
+    if ( !d->arch.arg_xlat_l1_pg )
+        return -ENOMEM;
+
+    idx = l2_table_offset(ARG_XLAT_START(v));
+    if ( !d->arch.arg_xlat_l1_pg[idx] )
+    {
+        l2_pgentry_t *l2tab;
+
+        pg = alloc_domheap_page(NULL, MEMF_node(domain_to_node(d)));
+        if ( !pg )
+            return -ENOMEM;
+        clear_domain_page(page_to_mfn(pg));
+        d->arch.arg_xlat_l1_pg[idx] = pg;
+
+        l2tab = __map_domain_page(d->arch.perdomain_l2_pg[ARG_XLAT_SLOT]);
+        l2tab[idx] = l2e_from_page(pg, __PAGE_HYPERVISOR);
+        unmap_domain_page(l2tab);
+    }
 
-    v->arch.compat_arg_xlat = alloc_xenheap_pages(order,
-                                                  MEMF_node(vcpu_to_node(v)));
+    l1tab = __map_domain_page(d->arch.arg_xlat_l1_pg[idx]);
+    idx = l1_table_offset(ARG_XLAT_START(v));
+    BUILD_BUG_ON(COMPAT_ARG_XLAT_SIZE > (1UL << ARG_XLAT_VA_SHIFT));
+    for ( i = 0; i < PFN_UP(COMPAT_ARG_XLAT_SIZE); ++i )
+    {
+        pg = alloc_domheap_page(NULL, MEMF_node(domain_to_node(d)));
+        if ( !pg )
+            return -ENOMEM;
+        l1tab[idx + i] = l1e_from_page(pg, __PAGE_HYPERVISOR);
+    }
+    unmap_domain_page(l1tab);
 
-    return v->arch.compat_arg_xlat ? 0 : -ENOMEM;
+    return 0;
 }
 
 void free_compat_arg_xlat(struct vcpu *v)
 {
-    unsigned int order = get_order_from_bytes(COMPAT_ARG_XLAT_SIZE);
+    struct domain *d = v->domain;
+    unsigned long start = ARG_XLAT_START(v);
+    unsigned long va = start + COMPAT_ARG_XLAT_SIZE - 1;
+    l1_pgentry_t *l1tab =
+        __map_domain_page(d->arch.arg_xlat_l1_pg[l2_table_offset(start)]);
+
+    do {
+        l1_pgentry_t l1e = l1tab[l1_table_offset(va)];
+
+        if ( l1e_get_flags(l1e) & _PAGE_PRESENT )
+        {
+            struct page_info *pg = l1e_get_page(l1e);
+
+            l1tab[l1_table_offset(va)] = l1e_empty();
+            flush_tlb_one_mask(d->domain_dirty_cpumask, va);
+            free_domheap_page(pg);
+        }
+        va -= PAGE_SIZE;
+    } while ( va >= start );
 
-    free_xenheap_pages(v->arch.compat_arg_xlat, order);
-    v->arch.compat_arg_xlat = NULL;
+    unmap_domain_page(l1tab);
 }
 
 void cleanup_frame_table(struct mem_hotadd_info *info)
--- a/xen/include/asm-x86/config.h
+++ b/xen/include/asm-x86/config.h
@@ -212,7 +212,7 @@ extern unsigned char boot_edid_info[128]
 /* Slot 260: per-domain mappings (including map cache). */
 #define PERDOMAIN_VIRT_START    (PML4_ADDR(260))
 #define PERDOMAIN_SLOT_MBYTES   (PML4_ENTRY_BYTES >> (20 + PAGETABLE_ORDER))
-#define PERDOMAIN_SLOTS         2
+#define PERDOMAIN_SLOTS         3
 #define PERDOMAIN_VIRT_SLOT(s)  (PERDOMAIN_VIRT_START + (s) * \
                                  (PERDOMAIN_SLOT_MBYTES << 20))
 /* Slot 261: machine-to-phys conversion table (256GB). */
@@ -304,6 +304,14 @@ extern unsigned long xen_phys_start;
 #define LDT_VIRT_START(v)    \
     (GDT_VIRT_START(v) + (64*1024))
 
+/* Argument translation area. The 2nd to last per-domain-mapping sub-area. */
+#define ARG_XLAT_SLOT            (PERDOMAIN_SLOTS - 2)
+/* Allow for at least one guard page (COMPAT_ARG_XLAT_SIZE being 2 pages): */
+#define ARG_XLAT_VA_SHIFT        (2 + PAGE_SHIFT)
+#define ARG_XLAT_VIRT_START      PERDOMAIN_VIRT_SLOT(ARG_XLAT_SLOT)
+#define ARG_XLAT_START(v)        \
+    (ARG_XLAT_VIRT_START + ((v)->vcpu_id << ARG_XLAT_VA_SHIFT))
+
 /* map_domain_page() map cache. The last per-domain-mapping sub-area. */
 #define MAPCACHE_VCPU_ENTRIES    (CONFIG_PAGING_LEVELS * CONFIG_PAGING_LEVELS)
 #define MAPCACHE_ENTRIES         (MAX_VIRT_CPUS * MAPCACHE_VCPU_ENTRIES)
@@ -313,7 +321,7 @@ extern unsigned long xen_phys_start;
                                   MAPCACHE_ENTRIES * PAGE_SIZE)
 
 #define PDPT_L1_ENTRIES       \
-    ((PERDOMAIN_VIRT_SLOT(PERDOMAIN_SLOTS - 1) - PERDOMAIN_VIRT_START) >> 
PAGE_SHIFT)
+    ((PERDOMAIN_VIRT_SLOT(PERDOMAIN_SLOTS - 2) - PERDOMAIN_VIRT_START) >> 
PAGE_SHIFT)
 #define PDPT_L2_ENTRIES       \
     ((PDPT_L1_ENTRIES + (1 << PAGETABLE_ORDER) - 1) >> PAGETABLE_ORDER)
 
--- a/xen/include/asm-x86/domain.h
+++ b/xen/include/asm-x86/domain.h
@@ -244,6 +244,7 @@ struct arch_domain
     void **perdomain_pts;
     struct page_info *perdomain_l2_pg[PERDOMAIN_SLOTS];
     struct page_info *perdomain_l3_pg;
+    struct page_info **arg_xlat_l1_pg;
 
     unsigned int hv_compat_vstart;
 
@@ -448,9 +449,6 @@ struct arch_vcpu
 
     /* A secondary copy of the vcpu time info. */
     XEN_GUEST_HANDLE(vcpu_time_info_t) time_info_guest;
-
-    void *compat_arg_xlat;
-
 } __cacheline_aligned;
 
 /* Shorthands to improve code legibility. */
--- a/xen/include/asm-x86/x86_64/uaccess.h
+++ b/xen/include/asm-x86/x86_64/uaccess.h
@@ -1,16 +1,15 @@
 #ifndef __X86_64_UACCESS_H
 #define __X86_64_UACCESS_H
 
-#define COMPAT_ARG_XLAT_VIRT_BASE compat_arg_xlat_virt_base()
+#define COMPAT_ARG_XLAT_VIRT_BASE ((void *)ARG_XLAT_START(current))
 #define COMPAT_ARG_XLAT_SIZE      (2*PAGE_SIZE)
 struct vcpu;
-void *compat_arg_xlat_virt_base(void);
 int setup_compat_arg_xlat(struct vcpu *v);
 void free_compat_arg_xlat(struct vcpu *v);
 #define is_compat_arg_xlat_range(addr, size) ({                               \
     unsigned long __off;                                                      \
     __off = (unsigned long)(addr) - (unsigned long)COMPAT_ARG_XLAT_VIRT_BASE; \
-    (__off <= COMPAT_ARG_XLAT_SIZE) &&                                        \
+    (__off < COMPAT_ARG_XLAT_SIZE) &&                                         \
     ((__off + (unsigned long)(size)) <= COMPAT_ARG_XLAT_SIZE);                \
 })

Attachment: x86-map-arg-xlat-area.patch
Description: Text document

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