mem: fix alignment of requested virtual areas

The original code did not align any addresses that were requested as
page-aligned, but were different because addr_is_hint was set.

Below fix by Dariusz has introduced an issue where all unaligned addresses
were left as unaligned.

This patch is a partial revert of
commit 7fa7216ed48d ("mem: fix alignment of requested virtual areas")

and implements a proper fix for this issue, by asking for alignment in all
but the following two cases:

1) page size is equal to system page size, or
2) we got an aligned requested address, and will not accept a different one

This ensures that alignment is performed in all cases, except for those we
can guarantee that the address will not need alignment.

Fixes: b7cc54187ea4 ("mem: move virtual area function in common directory")
Fixes: 7fa7216ed48d ("mem: fix alignment of requested virtual areas")
Cc: stable@dpdk.org
Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
Tested-by: Lei Yao <lei.a.yao@intel.com>
Acked-by: Dariusz Stojaczyk <dariuszx.stojaczyk@intel.com>

diff --git a/lib/librte_eal/common/eal_common_memory.c b/lib/librte_eal/common/eal_common_memory.c
index 659cc08..fbfb1b0 100644 (file)
--- a/lib/librte_eal/common/eal_common_memory.c
+++ b/lib/librte_eal/common/eal_common_memory.c
@@ -66,14 +66,17 @@ eal_get_virtual_area(void *requested_addr, size_t *size,
                addr_is_hint = true;
        }
 
-       /* if requested address is not aligned by page size, or if requested
-        * address is NULL, add page size to requested length as we may get an
-        * address that's aligned by system page size, which can be smaller than
-        * our requested page size. additionally, we shouldn't try to align if
-        * system page size is the same as requested page size.
+       /* we don't need alignment of resulting pointer in the following cases:
+        *
+        * 1. page size is equal to system size
+        * 2. we have a requested address, and it is page-aligned, and we will
+        *    be discarding the address if we get a different one.
+        *
+        * for all other cases, alignment is potentially necessary.
         */
        no_align = (requested_addr != NULL &&
-               ((uintptr_t)requested_addr & (page_sz - 1))) ||
+               requested_addr == RTE_PTR_ALIGN(requested_addr, page_sz) &&
+               !addr_is_hint) ||
                page_sz == system_page_sz;
 
        do {