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Re: [Xen-devel] [PATCH v6 04/13] Make MEM_ACCESS configurable

To: Stefano Stabellini <sstabellini@xxxxxxxxxx>
From: Julien Grall <julien.grall@xxxxxxx>
Date: Fri, 22 Jun 2018 02:51:53 +0100
Cc: artem_mygaiev@xxxxxxxx, lars.kurth@xxxxxxxxxx, andrii_anisov@xxxxxxxx, George.Dunlap@xxxxxxxxxxxxx, andrew.cooper3@xxxxxxxxxx, ian.jackson@xxxxxxxxxxxxx, dfaggioli@xxxxxxxx, tim@xxxxxxx, jbeulich@xxxxxxxx, wei.liu2@xxxxxxxxxx, dgdegra@xxxxxxxxxxxxx, xen-devel@xxxxxxxxxxxxx
Delivery-date: Fri, 22 Jun 2018 01:52:25 +0000
List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

Hi Stefano,

On 06/13/2018 10:14 PM, Stefano Stabellini wrote:

Select MEM_ACCESS_ALWAYS_ON on x86 to mark that MEM_ACCESS is not
configurable on x86. Avoid selecting it on ARM.
Rename HAS_MEM_ACCESS to MEM_ACCESS everywhere. Add a prompt and a
description to MEM_ACCESS in xen/common/Kconfig.

The result is that the user-visible option is MEM_ACCESS, and it is
configurable only on ARM (disabled by default). At the moment the
arch-specific mem_access code remains enabled on ARM, even with
MEM_ACCESS=y.

The purpose is to reduce code size. The option doesn't depend on EXPERT
because it would be nice to ecurity-support configurations without
MEM_ACCESS and a non-expert should be able to disable it.

Suggested-by: Julien Grall <julien.grall@xxxxxxx>
Signed-off-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>


Acked-by: Julien Grall <julien.grall@xxxxxxx>

Cheers,


CC: dgdegra@xxxxxxxxxxxxx
CC: andrew.cooper3@xxxxxxxxxx
CC: George.Dunlap@xxxxxxxxxxxxx
CC: ian.jackson@xxxxxxxxxxxxx
CC: jbeulich@xxxxxxxx
CC: julien.grall@xxxxxxx
CC: konrad.wilk@xxxxxxxxxx
CC: sstabellini@xxxxxxxxxx
CC: tim@xxxxxxx
CC: wei.liu2@xxxxxxxxxx

---
Changes in v5:
- change MEM_ACCESS_ALWAYS_ON to bool
- change default for MEM_ACCESS, default y if MEM_ACCESS_ALWAYS_ON

Changes in v4:
- remove HAS_MEM_ACCESS
- move MEM_ACCESS_ALWAYS_ON to common
- combile default and bool to def_bool

Changes in v3:
- keep HAS_MEM_ACCESS to mark that an arch can do MEM_ACCESS
- introduce MEM_ACCESS_ALWAYS_ON
- the main MEM_ACCESS option is in xen/common/Kconfig

Changes in v2:
- patch added
---
  tools/firmware/xen-dir/shim.config |  2 +-
  xen/arch/arm/Kconfig               |  1 -
  xen/arch/x86/Kconfig               |  2 +-
  xen/common/Kconfig                 | 10 +++++++++-
  xen/common/Makefile                |  2 +-
  xen/common/domctl.c                |  2 +-
  xen/include/xen/mem_access.h       |  4 ++--
  xen/include/xsm/dummy.h            |  2 +-
  xen/include/xsm/xsm.h              |  4 ++--
  xen/xsm/dummy.c                    |  2 +-
  xen/xsm/flask/hooks.c              |  4 ++--
  11 files changed, 21 insertions(+), 14 deletions(-)

diff --git a/tools/firmware/xen-dir/shim.config 
b/tools/firmware/xen-dir/shim.config
index 4d5630f..21d7075 100644
--- a/tools/firmware/xen-dir/shim.config
+++ b/tools/firmware/xen-dir/shim.config
@@ -29,7 +29,7 @@ CONFIG_COMPAT=y
  CONFIG_CORE_PARKING=y
  CONFIG_HAS_ALTERNATIVE=y
  CONFIG_HAS_EX_TABLE=y
-CONFIG_HAS_MEM_ACCESS=y
+CONFIG_MEM_ACCESS=y
  CONFIG_HAS_MEM_PAGING=y
  CONFIG_HAS_MEM_SHARING=y
  CONFIG_HAS_PDX=y
diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
index 66adce4..2b87111 100644
--- a/xen/arch/arm/Kconfig
+++ b/xen/arch/arm/Kconfig
@@ -17,7 +17,6 @@ config ARM
        def_bool y
        select HAS_ALTERNATIVE
        select HAS_DEVICE_TREE
-       select HAS_MEM_ACCESS
        select HAS_PASSTHROUGH
        select HAS_PDX

diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig

index f64fc56..9a85fe9 100644
--- a/xen/arch/x86/Kconfig
+++ b/xen/arch/x86/Kconfig
@@ -15,7 +15,7 @@ config X86
        select HAS_GDBSX
        select HAS_IOPORTS
        select HAS_KEXEC
-       select HAS_MEM_ACCESS
+       select MEM_ACCESS_ALWAYS_ON
        select HAS_MEM_PAGING
        select HAS_MEM_SHARING
        select HAS_NS16550
diff --git a/xen/common/Kconfig b/xen/common/Kconfig
index 9043dce..db6bb2d 100644
--- a/xen/common/Kconfig
+++ b/xen/common/Kconfig
@@ -20,9 +20,17 @@ config HAS_DEVICE_TREE
  config HAS_EX_TABLE
        bool

-config HAS_MEM_ACCESS

+config MEM_ACCESS_ALWAYS_ON
        bool

+config MEM_ACCESS

+       def_bool MEM_ACCESS_ALWAYS_ON
+       prompt "Memory Access and VM events" if !MEM_ACCESS_ALWAYS_ON
+       ---help---
+
+         Framework to configure memory access types for guests and receive
+         related events in userspace.
+
  config HAS_MEM_PAGING
        bool

diff --git a/xen/common/Makefile b/xen/common/Makefile

index 24d4752..6f2b3fc 100644
--- a/xen/common/Makefile
+++ b/xen/common/Makefile
@@ -22,7 +22,7 @@ obj-y += lib.o
  obj-$(CONFIG_NEEDS_LIST_SORT) += list_sort.o
  obj-$(CONFIG_LIVEPATCH) += livepatch.o livepatch_elf.o
  obj-y += lzo.o
-obj-$(CONFIG_HAS_MEM_ACCESS) += mem_access.o
+obj-$(CONFIG_MEM_ACCESS) += mem_access.o
  obj-y += memory.o
  obj-y += monitor.o
  obj-y += multicall.o
diff --git a/xen/common/domctl.c b/xen/common/domctl.c
index 9b7bc08..891ad58 100644
--- a/xen/common/domctl.c
+++ b/xen/common/domctl.c
@@ -1085,7 +1085,7 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) 
u_domctl)
          copyback = 1;
          break;

-#ifdef CONFIG_HAS_MEM_ACCESS

+#ifdef CONFIG_MEM_ACCESS
      case XEN_DOMCTL_set_access_required:
          if ( unlikely(current->domain == d) ) /* no domain_pause() */
              ret = -EPERM;
diff --git a/xen/include/xen/mem_access.h b/xen/include/xen/mem_access.h
index 5ab34c1..7e95eab 100644
--- a/xen/include/xen/mem_access.h
+++ b/xen/include/xen/mem_access.h
@@ -78,7 +78,7 @@ long p2m_set_mem_access_multi(struct domain *d,
   */
  int p2m_get_mem_access(struct domain *d, gfn_t gfn, xenmem_access_t *access);

-#ifdef CONFIG_HAS_MEM_ACCESS

+#ifdef CONFIG_MEM_ACCESS
  int mem_access_memop(unsigned long cmd,
                       XEN_GUEST_HANDLE_PARAM(xen_mem_access_op_t) arg);
  #else
@@ -88,7 +88,7 @@ int mem_access_memop(unsigned long cmd,
  {
      return -ENOSYS;
  }
-#endif /* CONFIG_HAS_MEM_ACCESS */
+#endif /* CONFIG_MEM_ACCESS */

#endif /* _XEN_MEM_ACCESS_H */diff --git a/xen/include/xsm/dummy.h b/xen/include/xsm/dummy.h

index ff6b2db..b0ac1f6 100644
--- a/xen/include/xsm/dummy.h
+++ b/xen/include/xsm/dummy.h
@@ -584,7 +584,7 @@ static XSM_INLINE int xsm_vm_event_control(XSM_DEFAULT_ARG 
struct domain *d, int
      return xsm_default_action(action, current->domain, d);
  }

-#ifdef CONFIG_HAS_MEM_ACCESS

+#ifdef CONFIG_MEM_ACCESS
  static XSM_INLINE int xsm_mem_access(XSM_DEFAULT_ARG struct domain *d)
  {
      XSM_ASSERT_ACTION(XSM_DM_PRIV);
diff --git a/xen/include/xsm/xsm.h b/xen/include/xsm/xsm.h
index f0c6fc7..7636bcb 100644
--- a/xen/include/xsm/xsm.h
+++ b/xen/include/xsm/xsm.h
@@ -143,7 +143,7 @@ struct xsm_operations {

int (*vm_event_control) (struct domain *d, int mode, int op);-#ifdef CONFIG_HAS_MEM_ACCESS

+#ifdef CONFIG_MEM_ACCESS
      int (*mem_access) (struct domain *d);
  #endif

@@ -582,7 +582,7 @@ static inline int xsm_vm_event_control (xsm_default_t def, struct domain *d, int

      return xsm_ops->vm_event_control(d, mode, op);
  }

-#ifdef CONFIG_HAS_MEM_ACCESS

+#ifdef CONFIG_MEM_ACCESS
  static inline int xsm_mem_access (xsm_default_t def, struct domain *d)
  {
      return xsm_ops->mem_access(d);
diff --git a/xen/xsm/dummy.c b/xen/xsm/dummy.c
index 6e75119..3290d04 100644
--- a/xen/xsm/dummy.c
+++ b/xen/xsm/dummy.c
@@ -127,7 +127,7 @@ void __init xsm_fixup_ops (struct xsm_operations *ops)

set_to_dummy_if_null(ops, vm_event_control);-#ifdef CONFIG_HAS_MEM_ACCESS

+#ifdef CONFIG_MEM_ACCESS
      set_to_dummy_if_null(ops, mem_access);
  #endif

diff --git a/xen/xsm/flask/hooks.c b/xen/xsm/flask/hooks.c

index 78bc326..7a3ccfa 100644
--- a/xen/xsm/flask/hooks.c
+++ b/xen/xsm/flask/hooks.c
@@ -1256,7 +1256,7 @@ static int flask_vm_event_control(struct domain *d, int 
mode, int op)
      return current_has_perm(d, SECCLASS_DOMAIN2, DOMAIN2__VM_EVENT);
  }

-#ifdef CONFIG_HAS_MEM_ACCESS

+#ifdef CONFIG_MEM_ACCESS
  static int flask_mem_access(struct domain *d)
  {
      return current_has_perm(d, SECCLASS_DOMAIN2, DOMAIN2__MEM_ACCESS);
@@ -1803,7 +1803,7 @@ static struct xsm_operations flask_ops = {

.vm_event_control = flask_vm_event_control,-#ifdef CONFIG_HAS_MEM_ACCESS

+#ifdef CONFIG_MEM_ACCESS
      .mem_access = flask_mem_access,
  #endif


--
Julien Grall

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References:
- [Xen-devel] [PATCH v6 0/13] arm: more kconfig configurability and small default configs
  - From: Stefano Stabellini
- [Xen-devel] [PATCH v6 04/13] Make MEM_ACCESS configurable
  - From: Stefano Stabellini

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