On 1/8/26 9:41 AM, Jan Beulich wrote:
On 07.01.2026 17:34, Oleksii Kurochko wrote:
Newer ACPI revisions define the MADT GICC entry with Length = 82 bytes [1].
The current BAD_MADT_GICC_ENTRY() check rejects entries whose length does not
match the known values, which leads to:
GICv3: No valid GICC entries exist.
as observed on the AmpereOne platform.
To fix this, import the logic from Linux commit 9eb1c92b47c7:
The BAD_MADT_GICC_ENTRY check is a little too strict because
it rejects MADT entries that don't match the currently known
lengths. We should remove this restriction to avoid problems
if the table length changes. Future code which might depend on
additional fields should be written to validate those fields
before using them, rather than trying to globally check
known MADT version lengths.
Link:
https://lkml.kernel.org/r/[email protected]
Signed-off-by: Jeremy Linton <[email protected]>
[[email protected]: added MADT macro comments]
Signed-off-by: Lorenzo Pieralisi <[email protected]>
Acked-by: Sudeep Holla <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Al Stone <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Signed-off-by: Will Deacon <[email protected]>
As ACPI_MADT_GICC_LENGTH is dropped, update the functions where it is
used. As we rewrite the MADT for hwdom, reuse the host GICC header length
instead of ACPI_MADT_GICC_LENGTH.
[1]
https://uefi.org/specs/ACPI/6.6/05_ACPI_Software_Programming_Model.html#gic-cpu-interface-gicc-structure
Reported-By: Yann Dirson <[email protected]>
Co-developed-by: Yann Sionneau <[email protected]>
Signed-off-by: Oleksii Kurochko <[email protected]>
Reviewed-by: Stefano Stabellini <[email protected]>
---
I ran CI tests where it made sense for this patch, as I don’t see any CI job
that builds Xen with CONFIG_ACPI=y:
https://gitlab.com/xen-project/people/olkur/xen/-/pipelines/2229673951
I also built Xen manually with CONFIG_ACPI=y enabled and tested it on the
AmpereOne platform.
---
Changes in v2:
- Update the commit message:
- Use more characters for commit ID.
- Drop 'import from'.
- Add Reviewed-by: Stefano Stabellini <[email protected]>.
Was this a legitimate thing to do, considering ...
- Make the local variables host_gicc const in gic_get_hwdom_madt_size().
(header variable isn't const as container_of() will discard 'const'
qualifier
and so compilation error will occur).
- Return 0 instead of panic() in gic_get_hwdom_madt_size().
... all of these (plus leaving partly unaddressed a comment from Julien)?
Probably you are right, it was to early. I will drop it and ask Stefano to
re-review.
--- a/xen/arch/arm/gic.c
+++ b/xen/arch/arm/gic.c
@@ -418,8 +418,18 @@ unsigned long gic_get_hwdom_madt_size(const struct domain
*d)
{
unsigned long madt_size;
+ struct acpi_subtable_header *header;
Why is there a blank line left between declarations? In unusual situations (very
many variables, for example) that may be okay, but otherwise the first blank
line
generally wants to separate decls from statements.
It was visually better for me to have header and host_gicc variable in a
"separate
block". I can drop a blank line.
Also Julien asked for this to be const. You claimed a compile error would occur
if you do, but afaict that's only because ...
+ const struct acpi_madt_generic_interrupt *host_gicc;
+
+ header = acpi_table_get_entry_madt(ACPI_MADT_TYPE_GENERIC_INTERRUPT, 0);
+ if ( !header )
+ return 0;
+
+ host_gicc = container_of(header, struct acpi_madt_generic_interrupt,
+ header);
... you don't use const properly here as well.
Oh, right, I missed to add const for the second argument of container_of().
Finally (possibly not for this patch, but mentioning since originally it was
pointed out as an option) the function imo wants to become __init anyway, for
(as said by Julien) its only caller being so.
I didn't put __init here as you mentioned it was pointed out as an option.
Anyway
I think I will put __init in the next patch version.
Thanks.
~ Oleksii
