path: root/arch/arm/include
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authorIan Campbell <ian.campbell@citrix.com>2013-03-07 07:17:25 +0000
committerKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2013-03-11 13:52:19 -0400
commit85323a991d40681023822e86ca95f38a75262026 (patch)
tree75fcebac6a9d98e90dd2d2e9e14d5938c49ae850 /arch/arm/include
parentc705c78c0d0835a4aa5d0d9a3422e3218462030c (diff)
xen: arm: mandate EABI and use generic atomic operations.
Rob Herring has observed that c81611c4e96f "xen: event channel arrays are xen_ulong_t and not unsigned long" introduced a compile failure when building without CONFIG_AEABI: /tmp/ccJaIZOW.s: Assembler messages: /tmp/ccJaIZOW.s:831: Error: even register required -- `ldrexd r5,r6,[r4]' Will Deacon pointed out that this is because OABI does not require even base registers for 64-bit values. We can avoid this by simply using the existing atomic64_xchg operation and the same containerof trick as used by the cmpxchg macros. However since this code is used on memory which is shared with the hypervisor we require proper atomic instructions and cannot use the generic atomic64 callbacks (which are based on spinlocks), therefore add a dependency on !GENERIC_ATOMIC64. Since we already depend on !CPU_V6 there isn't much downside to this. While thinking about this we also observed that OABI has different struct alignment requirements to EABI, which is a problem for hypercall argument structs which are shared with the hypervisor and which must be in EABI layout. Since I don't expect people to want to run OABI kernels on Xen depend on CONFIG_AEABI explicitly too (although it also happens to be enforced by the !GENERIC_ATOMIC64 requirement too). Signed-off-by: Ian Campbell <ian.campbell@citrix.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Rob Herring <robherring2@gmail.com> Acked-by: Stefano Stabellini <Stefano.Stabellini@eu.citrix.com> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Diffstat (limited to 'arch/arm/include')
1 files changed, 4 insertions, 21 deletions
diff --git a/arch/arm/include/asm/xen/events.h b/arch/arm/include/asm/xen/events.h
index 5c27696de14..8b1f37bfeee 100644
--- a/arch/arm/include/asm/xen/events.h
+++ b/arch/arm/include/asm/xen/events.h
@@ -2,6 +2,7 @@
#include <asm/ptrace.h>
+#include <asm/atomic.h>
enum ipi_vector {
@@ -15,26 +16,8 @@ static inline int xen_irqs_disabled(struct pt_regs *regs)
return raw_irqs_disabled_flags(regs->ARM_cpsr);
- * We cannot use xchg because it does not support 8-byte
- * values. However it is safe to use {ldr,dtd}exd directly because all
- * platforms which Xen can run on support those instructions.
- */
-static inline xen_ulong_t xchg_xen_ulong(xen_ulong_t *ptr, xen_ulong_t val)
- xen_ulong_t oldval;
- unsigned int tmp;
- wmb();
- asm volatile("@ xchg_xen_ulong\n"
- "1: ldrexd %0, %H0, [%3]\n"
- " strexd %1, %2, %H2, [%3]\n"
- " teq %1, #0\n"
- " bne 1b"
- : "=&r" (oldval), "=&r" (tmp)
- : "r" (val), "r" (ptr)
- : "memory", "cc");
- return oldval;
+#define xchg_xen_ulong(ptr, val) atomic64_xchg(container_of((ptr), \
+ atomic64_t, \
+ counter), (val))
#endif /* _ASM_ARM_XEN_EVENTS_H */