On 30/07/2018 16:22, Aneesh Kumar K.V wrote:
Michael Ellerman [off-list ref] writes:
quoted
Hi Laurent,
Just one comment below.
Laurent Dufour [off-list ref] writes:
quoted
diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c
index 96b8cd8a802d..41ed03245eb4 100644
--- a/arch/powerpc/platforms/pseries/lpar.c
+++ b/arch/powerpc/platforms/pseries/lpar.c
@@ -418,6 +418,73 @@ static void pSeries_lpar_hpte_invalidate(unsigned long slot, unsigned long vpn,
BUG_ON(lpar_rc != H_SUCCESS);
}
+
+/*
+ * As defined in the PAPR's section 14.5.4.1.8
+ * The control mask doesn't include the returned reference and change bit from
+ * the processed PTE.
+ */
+#define HBLKR_AVPN 0x0100000000000000UL
+#define HBLKR_CTRL_MASK 0xf800000000000000UL
+#define HBLKR_CTRL_SUCCESS 0x8000000000000000UL
+#define HBLKR_CTRL_ERRNOTFOUND 0x8800000000000000UL
+#define HBLKR_CTRL_ERRBUSY 0xa000000000000000UL
+
+/**
+ * H_BLOCK_REMOVE caller.
+ * @idx should point to the latest @param entry set with a PTEX.
+ * If PTE cannot be processed because another CPUs has already locked that
+ * group, those entries are put back in @param starting at index 1.
+ * If entries has to be retried and @retry_busy is set to true, these entries
+ * are retried until success. If @retry_busy is set to false, the returned
+ * is the number of entries yet to process.
+ */
+static unsigned long call_block_remove(unsigned long idx, unsigned long *param,
+ bool retry_busy)
+{
+ unsigned long i, rc, new_idx;
+ unsigned long retbuf[PLPAR_HCALL9_BUFSIZE];
+
+again:
+ new_idx = 0;
+ BUG_ON((idx < 2) || (idx > PLPAR_HCALL9_BUFSIZE));
I count 1 ..
quoted
+ if (idx < PLPAR_HCALL9_BUFSIZE)
+ param[idx] = HBR_END;
+
+ rc = plpar_hcall9(H_BLOCK_REMOVE, retbuf,
+ param[0], /* AVA */
+ param[1], param[2], param[3], param[4], /* TS0-7 */
+ param[5], param[6], param[7], param[8]);
+ if (rc == H_SUCCESS)
+ return 0;
+
+ BUG_ON(rc != H_PARTIAL);
2 ...
quoted
+ /* Check that the unprocessed entries were 'not found' or 'busy' */
+ for (i = 0; i < idx-1; i++) {
+ unsigned long ctrl = retbuf[i] & HBLKR_CTRL_MASK;
+
+ if (ctrl == HBLKR_CTRL_ERRBUSY) {
+ param[++new_idx] = param[i+1];
+ continue;
+ }
+
+ BUG_ON(ctrl != HBLKR_CTRL_SUCCESS
+ && ctrl != HBLKR_CTRL_ERRNOTFOUND);
3 ...
BUG_ON()s.
I know the code in this file is already pretty liberal with the use of
BUG_ON() but I'd prefer if we don't make it any worse.
Given this is an optimisation it seems like we should be able to fall
back to the existing implementation in the case of error (which will
probably then BUG_ON() 😂)
If there's some reason we can't then I guess I can live with it.
It would be nice to log the error in case we are not expecting the
error return. We recently did
https://marc.info/?i=20180629083904.29250-1-aneesh.kumar@linux.ibm.com
I'm not sure that a failure during an invalidation should just result in an
error message being displayed because the page remains accessible and could
potentially be accessed later.
A comment in the caller hash__tlb_flush(), is quite explicit about that:
/* If there's a TLB batch pending, then we must flush it because the
* pages are going to be freed and we really don't want to have a CPU
* access a freed page because it has a stale TLB
*/
Getting an error when adding an entry may not be fatal but when removing one,
this could lead to data being exposed.
Laurent.