Re: [PATCH] tmem stub for 3.4

["Jan Beulich" <jbeulich@novell.com>]

Why would failing with -ENODEV be more graceful than failing with -ENOSYS?
In my opinion it just makes eventual compatibility handling slightly more
convoluted on the kernel side, as it then will require checking for two
different return codes to distinguish non-fatal from possibly fatal failure.

Jan

>>> Dan Magenheimer <dan.magenheimer@oracle.com> 19.03.09 15:42 >>>
After lengthy discussion with Keir and Ian, we agreed that
it is too close to 3.4 freeze to put in the transcendent memory
(tmem) patch.  Instead, it will be added as soon as xen-unstable
unfreezes following 3.4.

This patch reserves the hypercall number for tmem and
adds a stub to allow tmem-modified guests to fail gracefully
on the 3.4 release.

(Patch also attached in case my mailer messes up the formatting.)

Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com>

diff -r 2039e8271051 xen/arch/x86/x86_32/entry.S
--- a/xen/arch/x86/x86_32/entry.S	Wed Mar 18 17:30:13 2009 +0000
+++ b/xen/arch/x86/x86_32/entry.S	Thu Mar 19 08:31:35 2009 -0600
@@ -703,6 +703,7 @@ ENTRY(hypercall_table)
         .long do_sysctl             /* 35 */
         .long do_domctl
         .long do_kexec_op
+        .long do_tmem_op
         .rept __HYPERVISOR_arch_0-((.-hypercall_table)/4)
         .long do_ni_hypercall
         .endr
@@ -750,6 +751,7 @@ ENTRY(hypercall_args_table)
         .byte 1 /* do_sysctl            */  /* 35 */
         .byte 1 /* do_domctl            */
         .byte 2 /* do_kexec_op          */
+        .byte 1 /* do_tmem_op           */
         .rept __HYPERVISOR_arch_0-(.-hypercall_args_table)
         .byte 0 /* do_ni_hypercall      */
         .endr
diff -r 2039e8271051 xen/arch/x86/x86_64/compat/entry.S
--- a/xen/arch/x86/x86_64/compat/entry.S	Wed Mar 18 17:30:13 2009 +0000
+++ b/xen/arch/x86/x86_64/compat/entry.S	Thu Mar 19 08:31:35 2009 -0600
@@ -408,6 +408,7 @@ ENTRY(compat_hypercall_table)
         .quad do_sysctl                 /* 35 */
         .quad do_domctl
         .quad compat_kexec_op
+        .quad do_tmem_op
         .rept __HYPERVISOR_arch_0-((.-compat_hypercall_table)/8)
         .quad compat_ni_hypercall
         .endr
@@ -455,6 +456,7 @@ ENTRY(compat_hypercall_args_table)
         .byte 1 /* do_sysctl                */  /* 35 */
         .byte 1 /* do_domctl                */
         .byte 2 /* compat_kexec_op          */
+        .byte 1 /* do_tmem_op               */
         .rept __HYPERVISOR_arch_0-(.-compat_hypercall_args_table)
         .byte 0 /* compat_ni_hypercall      */
         .endr
diff -r 2039e8271051 xen/arch/x86/x86_64/entry.S
--- a/xen/arch/x86/x86_64/entry.S	Wed Mar 18 17:30:13 2009 +0000
+++ b/xen/arch/x86/x86_64/entry.S	Thu Mar 19 08:31:35 2009 -0600
@@ -692,6 +692,7 @@ ENTRY(hypercall_table)
         .quad do_sysctl             /* 35 */
         .quad do_domctl
         .quad do_kexec_op
+        .quad do_tmem_op
         .rept __HYPERVISOR_arch_0-((.-hypercall_table)/8)
         .quad do_ni_hypercall
         .endr
@@ -739,6 +740,7 @@ ENTRY(hypercall_args_table)
         .byte 1 /* do_sysctl            */  /* 35 */
         .byte 1 /* do_domctl            */
         .byte 2 /* do_kexec             */
+        .byte 1 /* do_tmem_op           */
         .rept __HYPERVISOR_arch_0-(.-hypercall_args_table)
         .byte 0 /* do_ni_hypercall      */
         .endr
diff -r 2039e8271051 xen/common/memory.c
--- a/xen/common/memory.c	Wed Mar 18 17:30:13 2009 +0000
+++ b/xen/common/memory.c	Thu Mar 19 08:31:35 2009 -0600
@@ -560,6 +560,19 @@ long do_memory_op(unsigned long cmd, XEN
     return rc;
 }
 
+/* temporary placeholder for tmem hypercall */
+int do_tmem_op(void *tmem_op)
+{
+    static int warned = 0;
+
+    if ( !warned )
+    {
+        printk("tmem: not implemented\n");
+        warned = 1;
+    }
+    return -ENODEV;
+}
+
 /*
  * Local variables:
  * mode: C