On 18/10/19 5:46 pm, Christophe Leroy wrote:

Le 17/10/2019 à 09:36, Andrew Donnellan a écrit :

quoted

On 10/9/19 7:16 pm, Christophe Leroy wrote:

quoted

+#if defined(CONFIG_VMAP_STACK) && CONFIG_THREAD_SHIFT < PAGE_SHIFT
+#define THREAD_SHIFT        PAGE_SHIFT
+#else
  #define THREAD_SHIFT        CONFIG_THREAD_SHIFT
+#endif

  #define THREAD_SIZE        (1 << THREAD_SHIFT)

Looking at 64-bit book3s: with 64K pages, this results in a 
THREAD_SIZE that's too large for immediate mode arithmetic operations, 
which is annoying. Hmm.

Which operation are you thinking about ?

For instance, 'addi' can't be used anymore, but 'addis' can.

Right, I didn't look too closely - yes, they're "addi"s. But also 
DS-form stores:

	stdu	r1,THREAD_SIZE-STACK_FRAME_OVERHEAD(r3)

Anyway, this is just the first thing that broke when I wondered whether 
a ppc64le_defconfig would even build if I just switched on VMAP_STACK, 
I'll work around it

-- 
Andrew Donnellan              OzLabs, ADL Canberra
ajd@linux.ibm.com             IBM Australia Limited