On 7/18/2016 5:00 AM, Mark Rutland wrote:
Hi,
On Sun, Jul 17, 2016 at 02:45:59PM -0600, Jeffrey Hugo wrote:
+ if (status == EFI_BUFFER_TOO_SMALL ||
+ (*buff_size - *map_size) / sizeof(*m) < 8) {
efi_call_early(free_pool, m);
+ /*
+ * Make sure there is 8 entries worth of headroom so that the
+ * buffer can be reused for a new map after allocations are
+ * no longer permitted. Its unlikely that the map will grow to
+ * exceed this headroom once we are ready to trigger
+ * ExitBootServices()
+ */
+ *map_size += sizeof(*m) * 8;
It's probably worth having something like...
#define EFI_MMAP_NR_SLACK_SLOTS 8
... at the top of the file, and changing the comment here to not refer
to the specific value. That way we avoid duplicating the value, and
making it easier to modify / backport in future.
You are right, that does make sense. I'll wait a bit to see if there is
any other feedback, and add this suggestion to V2.
As a general note, it's a shame that we don't know desc_size first time
through. If descs grow, 8 * sizeof(*m) might be too small. That's an
existing problem though, so I guess it makes sense to be consistent and
use sizeof(*m) here.
Yep. Unless I've missed something, it seems like the two options are
either make a decent attempt to guess at desc_size the first time
(current approach), or intentionally fail the first time just to get the
size. The current approach doesn't seem perfect, but it does have a
chance at passing with just one attempt. I couldn't see a better
solution, but if someone else has an idea, I'd like to hear it.
Otherwise, this looks fine to me.
Thanks,
Mark.
--
Jeffrey Hugo
Qualcomm Datacenter Technologies as an affiliate of Qualcomm
Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.
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