This patch does not resolve the issue, reserved entries are still created. [ 0.000000] BIOS-e820: [mem 0x0000000280000000-0x00000002800fffff] reserved [ 0.000000] BIOS-e820: [mem 0x0000000290000000-0x000000029fffffff] reserved
# cat /proc/iomem 290000000-29fffffff : CXL Window 0 290000000-29fffffff : Reserved # cxl create-region -m -d decoder0.0 -w 1 -g 256 mem0 cxl region: create_region: region0: set_size failed: Numerical result out of range cxl region: cmd_create_region: created 0 regions On Tue, Oct 18, 2022 at 2:05 AM Ani Sinha <a...@anisinha.ca> wrote: > On Tue, Oct 18, 2022 at 5:14 AM Gregory Price <gourry.memve...@gmail.com> > wrote: > > > > Early-boot e820 records will be inserted by the bios/efi/early boot > > software and be reported to the kernel via insert_resource. Later, when > > CXL drivers iterate through the regions again, they will insert another > > resource and make the RESERVED memory area a child. > > I have already sent a patch > https://www.mail-archive.com/qemu-devel@nongnu.org/msg882012.html . > When the patch is applied, there would not be any reserved entries > even with passing E820_RESERVED . > So this patch needs to be evaluated in the light of the above patch I > sent. Once you apply my patch, does the issue still exist? > > > > > This RESERVED memory area causes the memory region to become unusable, > > and as a result attempting to create memory regions with > > > > `cxl create-region ...` > > > > Will fail due to the RESERVED area intersecting with the CXL window. > > > > > > During boot the following traceback is observed: > > > > 0xffffffff81101650 in insert_resource_expand_to_fit () > > 0xffffffff83d964c5 in e820__reserve_resources_late () > > 0xffffffff83e03210 in pcibios_resource_survey () > > 0xffffffff83e04f4a in pcibios_init () > > > > Which produces a call to reserve the CFMWS area: > > > > (gdb) p *new > > $54 = {start = 0x290000000, end = 0x2cfffffff, name = "Reserved", > > flags = 0x200, desc = 0x7, parent = 0x0, sibling = 0x0, > > child = 0x0} > > > > Later the Kernel parses ACPI tables and reserves the exact same area as > > the CXL Fixed Memory Window. The use of `insert_resource_conflict` > > retains the RESERVED region and makes it a child of the new region. > > > > 0xffffffff811016a4 in insert_resource_conflict () > > insert_resource () > > 0xffffffff81a81389 in cxl_parse_cfmws () > > 0xffffffff818c4a81 in call_handler () > > acpi_parse_entries_array () > > > > (gdb) p/x *new > > $59 = {start = 0x290000000, end = 0x2cfffffff, name = "CXL Window 0", > > flags = 0x200, desc = 0x0, parent = 0x0, sibling = 0x0, > > child = 0x0} > > > > This produces the following output in /proc/iomem: > > > > 590000000-68fffffff : CXL Window 0 > > 590000000-68fffffff : Reserved > > > > This reserved area causes `get_free_mem_region()` to fail due to a check > > against `__region_intersects()`. Due to this reserved area, the > > intersect check will only ever return REGION_INTERSECTS, which causes > > `cxl create-region` to always fail. > > > > Signed-off-by: Gregory Price <gregory.pr...@memverge.com> > > --- > > hw/i386/pc.c | 2 -- > > 1 file changed, 2 deletions(-) > > > > diff --git a/hw/i386/pc.c b/hw/i386/pc.c > > index 566accf7e6..5bf5465a21 100644 > > --- a/hw/i386/pc.c > > +++ b/hw/i386/pc.c > > @@ -1061,7 +1061,6 @@ void pc_memory_init(PCMachineState *pcms, > > hwaddr cxl_size = MiB; > > > > cxl_base = pc_get_cxl_range_start(pcms); > > - e820_add_entry(cxl_base, cxl_size, E820_RESERVED); > > memory_region_init(mr, OBJECT(machine), "cxl_host_reg", > cxl_size); > > memory_region_add_subregion(system_memory, cxl_base, mr); > > cxl_resv_end = cxl_base + cxl_size; > > @@ -1077,7 +1076,6 @@ void pc_memory_init(PCMachineState *pcms, > > memory_region_init_io(&fw->mr, OBJECT(machine), > &cfmws_ops, fw, > > "cxl-fixed-memory-region", > fw->size); > > memory_region_add_subregion(system_memory, fw->base, > &fw->mr); > > - e820_add_entry(fw->base, fw->size, E820_RESERVED); > > cxl_fmw_base += fw->size; > > cxl_resv_end = cxl_fmw_base; > > } > > -- > > 2.37.3 > > >
