[Qemu-devel] [RFC] target-arm: Provide mechanism for getting KVM constants even if not CONFIG_KVM

[Qemu-devel] [RFC] target-arm: Provide mechanism for getting KVM constants even if not CONFIG_KVM

[Peter Maydell]

There are a number of places where it would be convenient for ARM
code to have working definitions of KVM constants even in code
which is compiled with CONFIG_KVM not set. In this situation we
can't simply include the kernel KVM headers (which might conflict
with host header definitions or not even compile on the compiler
we're using) so we have to redefine equivalent constants.
Provide a mechanism for doing this and checking that the values
match, and use it for the constants we're currently exposing
via an ad-hoc mechanism.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
A series I'm currently working on wants another couple of KVM
constants outside CONFIG_KVM code (in that case it's the
KVM_ARM_TARGET_* values), and hw/arm/virt.c will want KVM_PSCI_*
constants. This is my attempt at at least putting all of our
redefinitions of things in one header file.

Does anybody think this is horribly ugly or have a better idea?

 target-arm/cpu.h        |   13 ++-----------
 target-arm/kvm-consts.h |   34 ++++++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 11 deletions(-)
 create mode 100644 target-arm/kvm-consts.h

diff --git a/target-arm/cpu.h b/target-arm/cpu.h
index 9f110f1..c3f007f 100644
--- a/target-arm/cpu.h
+++ b/target-arm/cpu.h
@@ -21,6 +21,8 @@
 
 #include "config.h"
 
+#include "kvm-consts.h"
+
 #if defined(TARGET_AARCH64)
   /* AArch64 definitions */
 #  define TARGET_LONG_BITS 64
@@ -497,17 +499,6 @@ void armv7m_nvic_complete_irq(void *opaque, int irq);
     (((cp) << 16) | ((is64) << 15) | ((crn) << 11) |    \
      ((crm) << 7) | ((opc1) << 3) | (opc2))
 
-/* Note that these must line up with the KVM/ARM register
- * ID field definitions (kvm.c will check this, but we
- * can't just use the KVM defines here as the kvm headers
- * are unavailable to non-KVM-specific files)
- */
-#define CP_REG_SIZE_SHIFT 52
-#define CP_REG_SIZE_MASK       0x00f0000000000000ULL
-#define CP_REG_SIZE_U32        0x0020000000000000ULL
-#define CP_REG_SIZE_U64        0x0030000000000000ULL
-#define CP_REG_ARM             0x4000000000000000ULL
-
 /* Convert a full 64 bit KVM register ID to the truncated 32 bit
  * version used as a key for the coprocessor register hashtable
  */
diff --git a/target-arm/kvm-consts.h b/target-arm/kvm-consts.h
new file mode 100644
index 0000000..42ffb50
--- /dev/null
+++ b/target-arm/kvm-consts.h
@@ -0,0 +1,34 @@
+/*
+ * Provide versions of KVM constant defines that can be used even
+ * when CONFIG_KVM is not set and we don't have access to the
+ * KVM headers. If CONFIG_KVM is set, we do a compile-time check
+ * that we haven't got out of sync somehow.
+ */
+#ifndef ARM_KVM_CONSTS_H
+#define ARM_KVM_CONSTS_H
+
+#ifdef CONFIG_KVM
+#include "qemu/compiler.h"
+#include <linux/kvm.h>
+
+#define MISMATCH_CHECK(X, Y) QEMU_BUILD_BUG_ON(X != Y)
+
+#else
+#define MISMATCH_CHECK(X, Y)
+#endif
+
+#define CP_REG_SIZE_SHIFT 52
+#define CP_REG_SIZE_MASK       0x00f0000000000000ULL
+#define CP_REG_SIZE_U32        0x0020000000000000ULL
+#define CP_REG_SIZE_U64        0x0030000000000000ULL
+#define CP_REG_ARM             0x4000000000000000ULL
+
+MISMATCH_CHECK(CP_REG_SIZE_SHIFT, KVM_REG_SIZE_SHIFT)
+MISMATCH_CHECK(CP_REG_SIZE_MASK, KVM_REG_SIZE_MASK)
+MISMATCH_CHECK(CP_REG_SIZE_U32, KVM_REG_SIZE_U32)
+MISMATCH_CHECK(CP_REG_SIZE_U64, KVM_REG_SIZE_U64)
+MISMATCH_CHECK(CP_REG_ARM, KVM_REG_ARM)
+
+#undef MISMATCH_CHECK
+
+#endif
-- 
1.7.9.5

Re: [Qemu-devel] [RFC] target-arm: Provide mechanism for getting KVM constants even if not CONFIG_KVM

[Paolo Bonzini]

Il 14/11/2013 20:07, Peter Maydell ha scritto:
> diff --git a/target-arm/kvm-consts.h b/target-arm/kvm-consts.h
> new file mode 100644
> index 0000000..42ffb50
> --- /dev/null
> +++ b/target-arm/kvm-consts.h
> @@ -0,0 +1,34 @@
> +/*
> + * Provide versions of KVM constant defines that can be used even
> + * when CONFIG_KVM is not set and we don't have access to the
> + * KVM headers. If CONFIG_KVM is set, we do a compile-time check
> + * that we haven't got out of sync somehow.
> + */
> +#ifndef ARM_KVM_CONSTS_H
> +#define ARM_KVM_CONSTS_H
> +
> +#ifdef CONFIG_KVM
> +#include "qemu/compiler.h"
> +#include <linux/kvm.h>
> +
> +#define MISMATCH_CHECK(X, Y) QEMU_BUILD_BUG_ON(X != Y)
> +
> +#else
> +#define MISMATCH_CHECK(X, Y)
> +#endif
> +
> +#define CP_REG_SIZE_SHIFT 52
> +#define CP_REG_SIZE_MASK       0x00f0000000000000ULL
> +#define CP_REG_SIZE_U32        0x0020000000000000ULL
> +#define CP_REG_SIZE_U64        0x0030000000000000ULL
> +#define CP_REG_ARM             0x4000000000000000ULL
> +
> +MISMATCH_CHECK(CP_REG_SIZE_SHIFT, KVM_REG_SIZE_SHIFT)
> +MISMATCH_CHECK(CP_REG_SIZE_MASK, KVM_REG_SIZE_MASK)
> +MISMATCH_CHECK(CP_REG_SIZE_U32, KVM_REG_SIZE_U32)
> +MISMATCH_CHECK(CP_REG_SIZE_U64, KVM_REG_SIZE_U64)
> +MISMATCH_CHECK(CP_REG_ARM, KVM_REG_ARM)
> +
> +#undef MISMATCH_CHECK
> +
> +#endif
> 

It's okay.  There are indeed advantages to putting this together with
the definitions, instead of splitting it between target-arm/cpu.h and
target-arm/kvm.c.

The patch is missing the removal of the check from kvm.c though.

Paolo

Re: [Qemu-devel] [RFC] target-arm: Provide mechanism for getting KVM constants even if not CONFIG_KVM

[Peter Maydell]

On 15 November 2013 10:54, Paolo Bonzini <pbonzini@redhat.com> wrote:
> It's okay.  There are indeed advantages to putting this together with
> the definitions, instead of splitting it between target-arm/cpu.h and
> target-arm/kvm.c.

Cool. I just wanted to check I wasn't missing some
clever approach to this that might have avoided the
need to duplicate all the definitions.

> The patch is missing the removal of the check from kvm.c though.

Yeah, I put this out in a bit of a hurry last thing in
the evening. You'll notice I forgot the copyright/license
boilerplate in the header comment too.

thanks
-- PMM

Re: [Qemu-devel] [RFC] target-arm: Provide mechanism for getting KVM constants even if not CONFIG_KVM

[Paolo Bonzini]

Il 15/11/2013 12:26, Peter Maydell ha scritto:
>> > It's okay.  There are indeed advantages to putting this together with
>> > the definitions, instead of splitting it between target-arm/cpu.h and
>> > target-arm/kvm.c.
> Cool. I just wanted to check I wasn't missing some
> clever approach to this that might have avoided the
> need to duplicate all the definitions.

If you call your constants KVM_FOO, the compiler should not warn for a
redefinition with the exact same content.  But I find that more gross
than clever...

Paolo

Re: [Qemu-devel] [RFC] target-arm: Provide mechanism for getting KVM constants even if not CONFIG_KVM

[Peter Maydell]

On 15 November 2013 11:33, Paolo Bonzini <pbonzini@redhat.com> wrote:
> Il 15/11/2013 12:26, Peter Maydell ha scritto:
>>> > It's okay.  There are indeed advantages to putting this together with
>>> > the definitions, instead of splitting it between target-arm/cpu.h and
>>> > target-arm/kvm.c.
>> Cool. I just wanted to check I wasn't missing some
>> clever approach to this that might have avoided the
>> need to duplicate all the definitions.
>
> If you call your constants KVM_FOO, the compiler should not warn for a
> redefinition with the exact same content.  But I find that more gross
> than clever...

Yeah, using different names seemed like a better idea to me
too.

-- PMM