[PATCH RFC for next] xen: make grant table configurable

* [PATCH RFC for next] xen: make grant table configurable
@ 2019-01-17 12:30 Wei Liu
  2019-01-17 17:36 ` Stefano Stabellini
                   ` (2 more replies)
  0 siblings, 3 replies; 9+ messages in thread
From: Wei Liu @ 2019-01-17 12:30 UTC (permalink / raw)
  To: xen-devel
  Cc: Stefano Stabellini, Wei Liu, Konrad Rzeszutek Wilk,
	George Dunlap, Andrew Cooper, Ian Jackson, Tim Deegan,
	Julien Grall, Jan Beulich, Roger Pau Monné

Introduce CONFIG_GRANT_TABLE. Provide stubs and make sure x86 and arm
hypervisors build with grant table disabled.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
---
I did this when I worked on splitting PV and HVM and thought this
might be useful and it was simple enough to get done.

RFC because I can envisage some configurations in the distant future
do away with grant table and event channel. There is small a benefit
to consider accepting this patch now so that Gitlab's randconf build
can start testing with grant table turned off right away.
---
 xen/arch/arm/setup.c              |  3 ++-
 xen/arch/arm/traps.c              |  2 ++
 xen/arch/x86/hvm/Makefile         |  2 +-
 xen/arch/x86/hvm/hypercall.c      |  4 ++++
 xen/arch/x86/hypercall.c          |  2 ++
 xen/arch/x86/pv/Makefile          |  2 +-
 xen/arch/x86/pv/hypercall.c       |  2 ++
 xen/arch/x86/setup.c              |  6 +++--
 xen/common/Kconfig                | 11 +++++++++
 xen/common/Makefile               |  2 +-
 xen/include/asm-arm/grant_table.h |  4 +++-
 xen/include/xen/grant_table.h     | 49 +++++++++++++++++++++++++++++++++++++--
 12 files changed, 80 insertions(+), 9 deletions(-)

diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
index 444857a967..3cd3513928 100644
--- a/xen/arch/arm/setup.c
+++ b/xen/arch/arm/setup.c
@@ -740,7 +740,8 @@ void __init start_xen(unsigned long boot_phys_offset,
         .flags = XEN_DOMCTL_CDF_hvm_guest | XEN_DOMCTL_CDF_hap,
         .max_evtchn_port = -1,
         .max_grant_frames = gnttab_dom0_frames(),
-        .max_maptrack_frames = opt_max_maptrack_frames,
+        .max_maptrack_frames = IS_ENABLED(CONFIG_GRANT_TABLE) ?
+                               opt_max_maptrack_frames : 0,
     };
 
     dcache_line_bytes = read_dcache_line_bytes();
diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 221c762ada..0f1c1b6431 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -1392,7 +1392,9 @@ static arm_hypercall_t arm_hypercall_table[] = {
     HYPERCALL_DEPRECATED(physdev_op_compat, 1),
     HYPERCALL(sysctl, 2),
     HYPERCALL(hvm_op, 2),
+#ifdef CONFIG_GRANT_TABLE
     HYPERCALL(grant_table_op, 3),
+#endif
     HYPERCALL(multicall, 2),
     HYPERCALL(platform_op, 1),
     HYPERCALL_ARM(vcpu_op, 3),
diff --git a/xen/arch/x86/hvm/Makefile b/xen/arch/x86/hvm/Makefile
index 86b106f8e7..43e5f3a21f 100644
--- a/xen/arch/x86/hvm/Makefile
+++ b/xen/arch/x86/hvm/Makefile
@@ -7,7 +7,7 @@ obj-y += dm.o
 obj-bin-y += dom0_build.init.o
 obj-y += domain.o
 obj-y += emulate.o
-obj-y += grant_table.o
+obj-$(CONFIG_GRANT_TABLE) += grant_table.o
 obj-y += hpet.o
 obj-y += hvm.o
 obj-y += hypercall.o
diff --git a/xen/arch/x86/hvm/hypercall.c b/xen/arch/x86/hvm/hypercall.c
index 19d126377a..1f667efc36 100644
--- a/xen/arch/x86/hvm/hypercall.c
+++ b/xen/arch/x86/hvm/hypercall.c
@@ -47,6 +47,7 @@ static long hvm_memory_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
     return rc;
 }
 
+#ifdef CONFIG_GRANT_TABLE
 static long hvm_grant_table_op(
     unsigned int cmd, XEN_GUEST_HANDLE_PARAM(void) uop, unsigned int count)
 {
@@ -71,6 +72,7 @@ static long hvm_grant_table_op(
     else
         return compat_grant_table_op(cmd, uop, count);
 }
+#endif
 
 static long hvm_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
 {
@@ -119,7 +121,9 @@ static long hvm_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
 
 static const hypercall_table_t hvm_hypercall_table[] = {
     HVM_CALL(memory_op),
+#ifdef CONFIG_GRANT_TABLE
     HVM_CALL(grant_table_op),
+#endif
     COMPAT_CALL(vcpu_op),
     HVM_CALL(physdev_op),
     COMPAT_CALL(xen_version),
diff --git a/xen/arch/x86/hypercall.c b/xen/arch/x86/hypercall.c
index 032de8f8f8..9311b63c1e 100644
--- a/xen/arch/x86/hypercall.c
+++ b/xen/arch/x86/hypercall.c
@@ -47,7 +47,9 @@ const hypercall_args_t hypercall_args_table[NR_hypercalls] =
     ARGS(xen_version, 2),
     ARGS(console_io, 3),
     ARGS(physdev_op_compat, 1),
+#ifdef CONFIG_GRANT_TABLE
     ARGS(grant_table_op, 3),
+#endif
     ARGS(vm_assist, 2),
     COMP(update_va_mapping_otherdomain, 4, 5),
     ARGS(vcpu_op, 3),
diff --git a/xen/arch/x86/pv/Makefile b/xen/arch/x86/pv/Makefile
index 65bca04175..cf28434ba9 100644
--- a/xen/arch/x86/pv/Makefile
+++ b/xen/arch/x86/pv/Makefile
@@ -5,7 +5,7 @@ obj-y += emulate.o
 obj-y += emul-gate-op.o
 obj-y += emul-inv-op.o
 obj-y += emul-priv-op.o
-obj-y += grant_table.o
+obj-$(CONFIG_GRANT_TABLE) += grant_table.o
 obj-y += hypercall.o
 obj-y += iret.o
 obj-y += misc-hypercalls.o
diff --git a/xen/arch/x86/pv/hypercall.c b/xen/arch/x86/pv/hypercall.c
index 5d11911735..ee0a6da515 100644
--- a/xen/arch/x86/pv/hypercall.c
+++ b/xen/arch/x86/pv/hypercall.c
@@ -53,7 +53,9 @@ const hypercall_table_t pv_hypercall_table[] = {
     COMPAT_CALL(xen_version),
     HYPERCALL(console_io),
     COMPAT_CALL(physdev_op_compat),
+#ifdef CONFIG_GRANT_TABLE
     COMPAT_CALL(grant_table_op),
+#endif
     COMPAT_CALL(vm_assist),
     COMPAT_CALL(update_va_mapping_otherdomain),
     COMPAT_CALL(iret),
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 06eb483cb4..09ef0e90df 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -686,8 +686,10 @@ void __init noreturn __start_xen(unsigned long mbi_p)
     struct xen_domctl_createdomain dom0_cfg = {
         .flags = XEN_DOMCTL_CDF_s3_integrity,
         .max_evtchn_port = -1,
-        .max_grant_frames = opt_max_grant_frames,
-        .max_maptrack_frames = opt_max_maptrack_frames,
+        .max_grant_frames = IS_ENABLED(CONFIG_GRANT_TABLE) ?
+                            opt_max_grant_frames : 0,
+        .max_maptrack_frames = IS_ENABLED(CONFIG_GRANT_TABLE) ?
+                               opt_max_maptrack_frames : 0,
     };
 
     /* Critical region without IDT or TSS.  Any fault is deadly! */
diff --git a/xen/common/Kconfig b/xen/common/Kconfig
index a79cd40441..18e0be3d98 100644
--- a/xen/common/Kconfig
+++ b/xen/common/Kconfig
@@ -11,6 +11,17 @@ config COMPAT
 config CORE_PARKING
 	bool
 
+config GRANT_TABLE
+	bool "Grant table support"
+	default y
+	---help---
+	  Grant table provides a generic mechanism to memory sharing
+	  between domains. This shared memory interface underpins the
+	  split device drivers for block and network IO in a classic
+	  Xen setup.
+
+	  If unsure, say Y.
+
 config HAS_ALTERNATIVE
 	bool
 
diff --git a/xen/common/Makefile b/xen/common/Makefile
index 56fc201b6b..e748554a44 100644
--- a/xen/common/Makefile
+++ b/xen/common/Makefile
@@ -10,7 +10,7 @@ obj-y += event_2l.o
 obj-y += event_channel.o
 obj-y += event_fifo.o
 obj-$(CONFIG_CRASH_DEBUG) += gdbstub.o
-obj-y += grant_table.o
+obj-$(CONFIG_GRANT_TABLE) += grant_table.o
 obj-y += guestcopy.o
 obj-bin-y += gunzip.init.o
 obj-y += irq.o
diff --git a/xen/include/asm-arm/grant_table.h b/xen/include/asm-arm/grant_table.h
index 816e3c6d68..50a07b8b17 100644
--- a/xen/include/asm-arm/grant_table.h
+++ b/xen/include/asm-arm/grant_table.h
@@ -31,7 +31,9 @@ void gnttab_mark_dirty(struct domain *d, mfn_t mfn);
  * enough space for a large grant table
  */
 #define gnttab_dom0_frames()                                             \
-    min_t(unsigned int, opt_max_grant_frames, PFN_DOWN(_etext - _stext))
+    min_t(unsigned int,                                                  \
+          IS_ENABLED(CONFIG_GRANT_TABLE) ? opt_max_grant_frames : 0,     \
+          PFN_DOWN(_etext - _stext))
 
 #define gnttab_init_arch(gt)                                             \
 ({                                                                       \
diff --git a/xen/include/xen/grant_table.h b/xen/include/xen/grant_table.h
index 12e8a4b80b..f0498df727 100644
--- a/xen/include/xen/grant_table.h
+++ b/xen/include/xen/grant_table.h
@@ -29,11 +29,12 @@
 #include <asm/page.h>
 #include <asm/grant_table.h>
 
-struct grant_table;
-
 extern unsigned int opt_max_grant_frames;
 extern unsigned int opt_max_maptrack_frames;
 
+#ifdef CONFIG_GRANT_TABLE
+struct grant_table;
+
 /* Create/destroy per-domain grant table context. */
 int grant_table_init(struct domain *d, unsigned int max_grant_frames,
                      unsigned int max_maptrack_frames);
@@ -61,4 +62,48 @@ int gnttab_get_shared_frame(struct domain *d, unsigned long idx,
 int gnttab_get_status_frame(struct domain *d, unsigned long idx,
                             mfn_t *mfn);
 
+#else
+
+static inline int grant_table_init(struct domain *d,
+                                   unsigned int max_grant_frames,
+                                   unsigned int max_maptrack_frames)
+{
+    return 0;
+}
+
+static inline void grant_table_destroy(struct domain *d) {}
+
+static inline void grant_table_init_vcpu(struct vcpu *v) {}
+
+static inline void grant_table_warn_active_grants(struct domain *d) {}
+
+static inline void gnttab_release_mappings(struct domain *d) {}
+
+static inline int mem_sharing_gref_to_gfn(struct grant_table *gt,
+                                          grant_ref_t ref,
+                                          gfn_t *gfn, uint16_t *status)
+{
+    return -EINVAL;
+}
+
+static inline int gnttab_map_frame(struct domain *d, unsigned long idx,
+                                   gfn_t gfn, mfn_t *mfn)
+{
+    return -EINVAL;
+}
+
+static inline int gnttab_get_shared_frame(struct domain *d, unsigned long idx,
+                                          mfn_t *mfn)
+{
+    return -EINVAL;
+}
+
+static inline int gnttab_get_status_frame(struct domain *d, unsigned long idx,
+                                          mfn_t *mfn)
+{
+    return -EINVAL;
+}
+
+#endif /* CONFIG_GRANT_TABLE */
+
 #endif /* __XEN_GRANT_TABLE_H__ */
-- 
2.11.0


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