Re: [PATCH v3 0/5] arm64: SPE ACPI enablement

[Sudeep Holla <sudeep.holla@arm.com>]

On Thu, May 09, 2019 at 11:35:59AM +0100, Sudeep Holla wrote:
> On Thu, May 09, 2019 at 10:28:11AM +0100, Will Deacon wrote:

[...]

> >
> > Since SPE uses virtual addressing, we don't really care about the underlying
> > page layout so there's no need to use higher-order allocations. I suppose we
> > could theoretically map them at the pmd level in some cases, but ignoring
> > them should also be harmless and I suspect you can delete the check.
> >
>
> Yes, I did a quick look to see if we can do that, but couldn't find a clue.
> Not sure if that's any optimisation, we can use order from page_private
> and set the values accordingly ?
>
And I forgot to add the diff that I mentioned above, something like the
patch below.

Regards,
Sudeep

-->8

diff --git i/drivers/perf/arm_spe_pmu.c w/drivers/perf/arm_spe_pmu.c
index 7cb766dafe85..45cd62517080 100644
--- i/drivers/perf/arm_spe_pmu.c
+++ w/drivers/perf/arm_spe_pmu.c
@@ -827,7 +827,7 @@ static void arm_spe_pmu_read(struct perf_event *event)
 static void *arm_spe_pmu_setup_aux(struct perf_event *event, void **pages,
 				   int nr_pages, bool snapshot)
 {
-	int i, cpu = event->cpu;
+	int i, j, cpu = event->cpu;
 	struct page **pglist;
 	struct arm_spe_pmu_buf *buf;
 
@@ -859,11 +859,12 @@ static void *arm_spe_pmu_setup_aux(struct perf_event *event, void **pages,
 		struct page *page = virt_to_page(pages[i]);
 
 		if (PagePrivate(page)) {
-			pr_warn("unexpected high-order page for auxbuf!");
-			goto out_free_pglist;
+			for (j = 0; j < 1 << page_private(page); j++)
+				pglist[i + j] = page++;
+			i += j - 1;
+		} else {
+			pglist[i] = page;
 		}
-
-		pglist[i] = virt_to_page(pages[i]);
 	}
 
 	buf->base = vmap(pglist, nr_pages, VM_MAP, PAGE_KERNEL);