Re: [PATCH v2] cxl/test: Enforce PMD alignment for volatile mock regions

[Richard Cheng]

On Thu, May 21, 2026 at 01:24:49PM +0800, Alison Schofield wrote:
> On Thu, May 21, 2026 at 10:20:26AM -0700, Dave Jiang wrote:
> > 
> > 
> > On 5/21/26 1:32 AM, Richard Cheng wrote:
> > > 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() -> alloca_dax_region() fails:
> > > 
> > > """
> > >     cxl_dax_region dax_region1: probe with driver cxl_dax_region failed
> > >                                 with error -12
> > > """
> > > 
> > > Enfore 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>
> > 
> > Hi Richard,
> > I can't seem to apply this patch against v7.1-rc4. What base did you use?
> 
> Hunk headers are wrong. Maybe hand editing without reformatting.
> Diffstat is wrong too but that didn't affect application.
> 
> I'll wait for the v3.
> 
>
Hi Dave, Alison,

Sorry I hand eddited the sequence of this line
+                       .window_size = SZ_256M > PMD_SIZE ? SZ_256M : PMD_SIZE,
without reformat the patch.
I've sent a v3 with base commit SHA as well.
Please take a look while you're available, thanks!

Best regards,
Richard Cheng.
 
> > 
> > DJ
> > 
> > 
> > 
> > > ---
> > > Changelog:
> > > 
> > > 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()
> > > 
> > > v1 link: https://lore.kernel.org/r/20260519233523.5991-1-icheng@xxxxxxxxxx/
> > > 
> > > Best regards,
> > > Richard Cheng.
> > > ---
> > >  tools/testing/cxl/test/cxl.c | 14 ++++++++++++--
> > >  1 file changed, 12 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/tools/testing/cxl/test/cxl.c b/tools/testing/cxl/test/cxl.c
> > > index 418669927fb0..09c309af5fd1 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 +495,17 @@ 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 +1834,8 @@ static __init int cxl_test_init(void)
> > >  	int rc, i;
> > >  	struct range mappable;
> > >  
> > > +	BUILD_BUG_ON(!IS_ALIGNED(MOCK_AUTO_REGION_SIZE_DEFAULT, PMD_SIZE));
> > > +
> > >  	cxl_acpi_test();
> > >  	cxl_core_test();
> > >  	cxl_mem_test();
> >