xen: move alloc/free_vcpu_struct() to common code

alloc_vcpu_struct() and free_vcpu_struct() contain little
architecture-specific logic and are suitable for sharing across
architectures. Move both helpers to common code.

To support the remaining architectural differences, introduce
arch_vcpu_struct_memflags(), allowing architectures to override the
memory flags passed to alloc_xenheap_pages(). This is currently needed
by x86, which may require MEMF_bits(32) for HVM guests using shadow
paging.

The ARM implementation of alloc/free_vcpu_struct() is removed and
replaced by the common version. Stub implementations are also dropped
from PPC and RISC-V.

Now that the size of struct vcpu for Arm64 is smaller than PAGE_SIZE,
MAX_PAGES_PER_VCPU is no longer needed and is removed.

Finally, make alloc_vcpu_struct() and free_vcpu_struct() static to
common/domain.c, as they are no longer used outside common code.

No functional changes.

Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Michal Orzel <michal.orzel@amd.com>

xen/arch/arm/domain.c

@@ -473,23 +473,6 @@ void dump_pageframe_info(struct domain *d)
 
 }
 
-struct vcpu *alloc_vcpu_struct(const struct domain *d)
-{
-    struct vcpu *v;
-
-    BUILD_BUG_ON(sizeof(*v) > PAGE_SIZE);
-    v = alloc_xenheap_page();
-    if ( v != NULL )
-        clear_page(v);
-
-    return v;
-}
-
-void free_vcpu_struct(struct vcpu *v)
-{
-    free_xenheap_page(v);
-}
-
 int arch_vcpu_create(struct vcpu *v)
 {
     int rc = 0;

xen/arch/ppc/stubs.c

@@ -152,11 +152,6 @@ void dump_pageframe_info(struct domain *d)
     BUG_ON("unimplemented");
 }
 
-void free_vcpu_struct(struct vcpu *v)
-{
-    BUG_ON("unimplemented");
-}
-
 int arch_vcpu_create(struct vcpu *v)
 {
     BUG_ON("unimplemented");
@@ -264,11 +259,6 @@ void vcpu_kick(struct vcpu *v)
     BUG_ON("unimplemented");
 }
 
-struct vcpu *alloc_vcpu_struct(const struct domain *d)
-{
-    BUG_ON("unimplemented");
-}
-
 unsigned long
 hypercall_create_continuation(unsigned int op, const char *format, ...)
 {

xen/arch/riscv/stubs.c

@@ -121,11 +121,6 @@ void dump_pageframe_info(struct domain *d)
     BUG_ON("unimplemented");
 }
 
-void free_vcpu_struct(struct vcpu *v)
-{
-    BUG_ON("unimplemented");
-}
-
 int arch_vcpu_create(struct vcpu *v)
 {
     BUG_ON("unimplemented");
@@ -233,11 +228,6 @@ void vcpu_kick(struct vcpu *v)
     BUG_ON("unimplemented");
 }
 
-struct vcpu *alloc_vcpu_struct(const struct domain *d)
-{
-    BUG_ON("unimplemented");
-}
-
 unsigned long
 hypercall_create_continuation(unsigned int op, const char *format, ...)
 {

xen/arch/x86/domain.c

@@ -493,30 +493,6 @@ unsigned int arch_domain_struct_memflags(void)
     return MEMF_bits(bits);
 }
 
-struct vcpu *alloc_vcpu_struct(const struct domain *d)
-{
-    struct vcpu *v;
-    /*
-     * This structure contains embedded PAE PDPTEs, used when an HVM guest
-     * runs on shadow pagetables outside of 64-bit mode. In this case the CPU
-     * may require that the shadow CR3 points below 4GB, and hence the whole
-     * structure must satisfy this restriction. Thus we specify MEMF_bits(32).
-     */
-    unsigned int memflags =
-        (is_hvm_domain(d) && paging_mode_shadow(d)) ? MEMF_bits(32) : 0;
-
-    BUILD_BUG_ON(sizeof(*v) > PAGE_SIZE);
-    v = alloc_xenheap_pages(0, memflags);
-    if ( v != NULL )
-        clear_page(v);
-    return v;
-}
-
-void free_vcpu_struct(struct vcpu *v)
-{
-    free_xenheap_page(v);
-}
-
 /* Initialise various registers to their architectural INIT/RESET state. */
 void arch_vcpu_regs_init(struct vcpu *v)
 {

xen/arch/x86/include/asm/domain.h

@@ -15,6 +15,18 @@
 unsigned int arch_domain_struct_memflags(void);
 #define arch_domain_struct_memflags arch_domain_struct_memflags
 
+/*
+ * This structure contains embedded PAE PDPTEs, used when an HVM guest
+ * runs on shadow pagetables outside of 64-bit mode. In this case the CPU
+ * may require that the shadow CR3 points below 4GB, and hence the whole
+ * structure must satisfy this restriction. Thus we specify MEMF_bits(32).
+ */
+#define arch_vcpu_struct_memflags(d) ({                                 \
+    const struct domain *d_ = (d);                                      \
+                                                                        \
+    (is_hvm_domain(d_) && paging_mode_shadow(d_) ? MEMF_bits(32) : 0);  \
+})
+
 #define has_32bit_shinfo(d)    ((d)->arch.has_32bit_shinfo)
 
 /*

xen/common/domain.c

@@ -316,6 +316,26 @@ static void vcpu_info_reset(struct vcpu *v)
          : &dummy_vcpu_info);
 }
 
+static struct vcpu *alloc_vcpu_struct(const struct domain *d)
+{
+#ifndef arch_vcpu_struct_memflags
+# define arch_vcpu_struct_memflags(d) ((void)(d), 0)
+#endif
+    struct vcpu *v;
+
+    BUILD_BUG_ON(sizeof(*v) > PAGE_SIZE);
+    v = alloc_xenheap_pages(0, arch_vcpu_struct_memflags(d));
+    if ( v )
+        clear_page(v);
+
+    return v;
+}
+
+static void free_vcpu_struct(struct vcpu *v)
+{
+    free_xenheap_page(v);
+}
+
 static void vmtrace_free_buffer(struct vcpu *v)
 {
     const struct domain *d = v->domain;

xen/include/xen/domain.h

@@ -70,10 +70,6 @@ void domid_free(domid_t domid);
 struct domain *alloc_domain_struct(void);
 void free_domain_struct(struct domain *d);
 
-/* Allocate/free a VCPU structure. */
-struct vcpu *alloc_vcpu_struct(const struct domain *d);
-void free_vcpu_struct(struct vcpu *v);
-
 /* Allocate/free a PIRQ structure. */
 #ifndef alloc_pirq_struct
 struct pirq *alloc_pirq_struct(struct domain *d);