[PATCH v4] cxl/test: Enforce PMD alignment for volatile mock regions

[Richard Cheng]

cxl_test allocates synthetic CFMWS HPA windows from a gen_pool with
SZ_256M alignment. On arm64 with CONFIG_ARM64_64K_PAGES=y and
CONFIG_PGTABLE_LEVELS=3, PMD_SIZE is 512M, so every CXL region carved
from a volatile window inherits a non-PMD-aligned start, and
cxl_dax_region_probe() -> alloc_dax_region() fails:

"""
    cxl_dax_region dax_region1: probe with driver cxl_dax_region failed
                                with error -12
"""

Enforce that every volatile mock CFMWS is PMD-aligned in both start and
size

Reviewed-by: Dave Jiang <dave.jiang@xxxxxxxxx>
Acked-by: Kai-Heng Feng <kaihengf@xxxxxxxxxx>
Signed-off-by: Richard Cheng <icheng@xxxxxxxxxx>
---
Changelog:

v3->v4:
    - Replace compile-time BUILD_BUG_ON() with runtime
      IS_ALIGNED(mock_auto_region_size, PMD_SIZE) check in
cxl_test_init().

v2->v3:
    - Correct hunk headers
    - Add base commit SHA

v1->v2:
    - Reframe from "fix start alignment" to "enforce PMD invariant for
      volatile CFMWS"
    - Bump cfmws5.window_size to max(SZ_256M, PMD_SIZE)
    - Gate populate_cedt() alignment on
      ACPI_CEDT_CFMWS_RESTRICT_VOLATILE so PMEM windows stay at SZ_256M
    - Add BUILD_BUG_ON for MOCK_AUTO_REGION_SIZE_DEFAULT v.s. PMD_SIZE
      in cxl_test_init()

Best regards,
Richard Cheng.
---
 tools/testing/cxl/test/cxl.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/tools/testing/cxl/test/cxl.c b/tools/testing/cxl/test/cxl.c
index 418669927fb0..6f8fa7504cad 100644
--- a/tools/testing/cxl/test/cxl.c
+++ b/tools/testing/cxl/test/cxl.c
@@ -318,7 +318,7 @@ static struct {
 			.restrictions = ACPI_CEDT_CFMWS_RESTRICT_HOSTONLYMEM |
 					ACPI_CEDT_CFMWS_RESTRICT_VOLATILE,
 			.qtg_id = FAKE_QTG_ID,
-			.window_size = SZ_256M,
+			.window_size = SZ_256M > PMD_SIZE ? SZ_256M : PMD_SIZE,
 		},
 		.target = { 3 },
 	},
@@ -495,9 +495,12 @@ static int populate_cedt(void)
 
 	for (i = cfmws_start; i <= cfmws_end; i++) {
 		struct acpi_cedt_cfmws *window = mock_cfmws[i];
+		int align = SZ_256M;
 
 		cfmws_elc_update(window, i);
-		res = alloc_mock_res(window->window_size, SZ_256M);
+		if (window->restrictions & ACPI_CEDT_CFMWS_RESTRICT_VOLATILE)
+			align = max_t(int, SZ_256M, PMD_SIZE);
+		res = alloc_mock_res(window->window_size, align);
 		if (!res)
 			return -ENOMEM;
 		window->base_hpa = res->range.start;
@@ -1826,6 +1829,12 @@ static __init int cxl_test_init(void)
 	int rc, i;
 	struct range mappable;
 
+	if (!IS_ALIGNED(mock_auto_region_size, PMD_SIZE)) {
+		pr_err_once("mock_auto_region_size %d must be PMD-aligned\n",
+			    mock_auto_region_size);
+		return -EINVAL;
+	}
+
 	cxl_acpi_test();
 	cxl_core_test();
 	cxl_mem_test();

base-commit: 507bd4b66c85d5b65696150cc16d31ac0b2ab151
-- 
2.43.0