On Mon, Feb 01, 2016 at 02:01:09PM +0530, Anshuman Khandual wrote:

On 01/29/2016 10:54 AM, David Gibson wrote:

quoted

+
+static int pseries_lpar_resize_hpt_commit(void *data)
+{
+	struct hpt_resize_state *state = data;
+
+	state->commit_rc = plpar_resize_hpt_commit(0, state->shift);
+	if (state->commit_rc != H_SUCCESS)
+		return -EIO;
+
+	/* Hypervisor has transitioned the HTAB, update our globals */
+	ppc64_pft_size = state->shift;
+	htab_size_bytes = 1UL << ppc64_pft_size;
+	htab_hash_mask = (htab_size_bytes >> 7) - 1;
+
+	return 0;
+}
+

snip

quoted

+/* Must be called in user context */
+static int pseries_lpar_resize_hpt(unsigned long shift)
+{
+	struct hpt_resize_state state = {
+		.shift = shift,
+		.commit_rc = H_FUNCTION,

quoted

+
+	rc = stop_machine(pseries_lpar_resize_hpt_commit, &state, NULL);

With my limited knowledge of stop_machine, wondering if the current
or any future version of 'pseries_lpar_resize_hpt_commit' function
can cause HPT change (page fault path) while stop is executing it.

It can, but the H_RESIZE_HPT_COMMIT hypercall is synchronous so the
cpu executing it can't make any HPT updates during it.  The
stop_machine() prevents any other cpus doing HPT updates.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson