[PATCH v1] xen: move alloc/free_vcpu_struct() to common code

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

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.

Move the definition of MAX_PAGES_PER_VCPU to xen/domain.h and default
it to 1. Retain the ARM64 exception (with CONFIG_NEW_VGIC) where two
pages are required due to larger per-IRQ structures.

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.

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@xxxxxxxxx>
---
CI tests: https://gitlab.com/xen-project/people/olkur/xen/-/pipelines/2219693055

Shouldn't we make alloc_domain_struct() and free_domain_struct() static and
drop their declarations from xen/domain.h, since these functions are only
used in common/domain.c?
---
 xen/arch/arm/domain.c             | 32 -------------------------------
 xen/arch/arm/include/asm/domain.h |  8 ++++++++
 xen/arch/ppc/stubs.c              | 10 ----------
 xen/arch/riscv/stubs.c            | 10 ----------
 xen/arch/x86/domain.c             | 23 ++--------------------
 xen/arch/x86/include/asm/domain.h |  3 +++
 xen/common/domain.c               | 27 ++++++++++++++++++++++++++
 xen/include/xen/domain.h          |  8 ++++----
 8 files changed, 44 insertions(+), 77 deletions(-)

diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
index 47973f99d9..507df807ed 100644
--- a/xen/arch/arm/domain.c
+++ b/xen/arch/arm/domain.c
@@ -473,38 +473,6 @@ void dump_pageframe_info(struct domain *d)
 
 }
 
-/*
- * The new VGIC has a bigger per-IRQ structure, so we need more than one
- * page on ARM64. Cowardly increase the limit in this case.
- */
-#if defined(CONFIG_NEW_VGIC) && defined(CONFIG_ARM_64)
-#define MAX_PAGES_PER_VCPU  2
-#else
-#define MAX_PAGES_PER_VCPU  1
-#endif
-
-struct vcpu *alloc_vcpu_struct(const struct domain *d)
-{
-    struct vcpu *v;
-
-    BUILD_BUG_ON(sizeof(*v) > MAX_PAGES_PER_VCPU * PAGE_SIZE);
-    v = alloc_xenheap_pages(get_order_from_bytes(sizeof(*v)), 0);
-    if ( v != NULL )
-    {
-        unsigned int i;
-
-        for ( i = 0; i < DIV_ROUND_UP(sizeof(*v), PAGE_SIZE); i++ )
-            clear_page((void *)v + i * PAGE_SIZE);
-    }
-
-    return v;
-}
-
-void free_vcpu_struct(struct vcpu *v)
-{
-    free_xenheap_pages(v, get_order_from_bytes(sizeof(*v)));
-}
-
 int arch_vcpu_create(struct vcpu *v)
 {
     int rc = 0;
diff --git a/xen/arch/arm/include/asm/domain.h 
b/xen/arch/arm/include/asm/domain.h
index 758ad807e4..f33d886bb8 100644
--- a/xen/arch/arm/include/asm/domain.h
+++ b/xen/arch/arm/include/asm/domain.h
@@ -12,6 +12,14 @@
 #include <asm/vpl011.h>
 #include <public/hvm/params.h>
 
+/*
+ * The new VGIC has a bigger per-IRQ structure, so we need more than one
+ * page on ARM64. Cowardly increase the limit in this case.
+ */
+#if defined(CONFIG_NEW_VGIC) && defined(CONFIG_ARM_64)
+#define MAX_PAGES_PER_VCPU  2
+#endif
+
 struct hvm_domain
 {
     uint64_t              params[HVM_NR_PARAMS];
diff --git a/xen/arch/ppc/stubs.c b/xen/arch/ppc/stubs.c
index 9953ea1c6c..f7f6e7ed97 100644
--- a/xen/arch/ppc/stubs.c
+++ b/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, ...)
 {
diff --git a/xen/arch/riscv/stubs.c b/xen/arch/riscv/stubs.c
index fe7d85ee1d..579c4215c8 100644
--- a/xen/arch/riscv/stubs.c
+++ b/xen/arch/riscv/stubs.c
@@ -126,11 +126,6 @@ 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");
@@ -238,11 +233,6 @@ 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, ...)
 {
diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index 7632d5e2d6..0e3f7de524 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -493,28 +493,9 @@ unsigned int arch_domain_struct_memflags(void)
     return MEMF_bits(bits);
 }
 
-struct vcpu *alloc_vcpu_struct(const struct domain *d)
+unsigned int arch_vcpu_struct_memflags(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);
+    return (is_hvm_domain(d) && paging_mode_shadow(d)) ? MEMF_bits(32) : 0;
 }
 
 /* Initialise various registers to their architectural INIT/RESET state. */
diff --git a/xen/arch/x86/include/asm/domain.h 
b/xen/arch/x86/include/asm/domain.h
index 7e5cbd11a4..576f9202b4 100644
--- a/xen/arch/x86/include/asm/domain.h
+++ b/xen/arch/x86/include/asm/domain.h
@@ -15,6 +15,9 @@
 unsigned int arch_domain_struct_memflags(void);
 #define arch_domain_struct_memflags arch_domain_struct_memflags
 
+unsigned int arch_vcpu_struct_memflags(const struct domain *d);
+#define arch_vcpu_struct_memflags arch_vcpu_struct_memflags
+
 #define has_32bit_shinfo(d)    ((d)->arch.has_32bit_shinfo)
 
 /*
diff --git a/xen/common/domain.c b/xen/common/domain.c
index 93c71bc766..3982d9e466 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -13,6 +13,7 @@
 #include <xen/sched.h>
 #include <xen/sections.h>
 #include <xen/domain.h>
+#include <xen/macros.h>
 #include <xen/mm.h>
 #include <xen/event.h>
 #include <xen/vm_event.h>
@@ -392,6 +393,32 @@ static int vcpu_teardown(struct vcpu *v)
     return 0;
 }
 
+static struct vcpu *alloc_vcpu_struct(const struct domain *d)
+{
+#ifndef arch_vcpu_struct_memflags
+# define arch_vcpu_struct_memflags(d) 0
+#endif
+    struct vcpu *v;
+    unsigned int order = get_order_from_bytes(sizeof(*v));
+
+    BUILD_BUG_ON(sizeof(*v) > MAX_PAGES_PER_VCPU * PAGE_SIZE);
+    v = alloc_xenheap_pages(order, arch_vcpu_struct_memflags(d));
+    if ( v )
+    {
+        unsigned int i;
+
+        for ( i = 0; i < DIV_ROUND_UP(sizeof(*v), PAGE_SIZE); i++ )
+            clear_page((void *)v + i * PAGE_SIZE);
+    }
+
+    return v;
+}
+
+static void free_vcpu_struct(struct vcpu *v)
+{
+    free_xenheap_pages(v, get_order_from_bytes(sizeof(*v)));
+}
+
 /*
  * Destoy a vcpu once all references to it have been dropped.  Used either
  * from domain_destroy()'s RCU path, or from the vcpu_create() error path
diff --git a/xen/include/xen/domain.h b/xen/include/xen/domain.h
index 8aab05ae93..3946ec9dad 100644
--- a/xen/include/xen/domain.h
+++ b/xen/include/xen/domain.h
@@ -15,6 +15,10 @@ struct guest_area {
 
 #include <asm/domain.h>
 
+#ifndef MAX_PAGES_PER_VCPU
+#define MAX_PAGES_PER_VCPU 1
+#endif
+
 typedef union {
     struct vcpu_guest_context *nat;
     struct compat_vcpu_guest_context *cmp;
@@ -70,10 +74,6 @@ 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);
-- 
2.52.0