On Tue, Jan 18, 2022 at 10:40:50AM +0100, Borislav Petkov wrote:
n Thu, Jan 13, 2022 at 04:28:39PM -0800, Lucas De Marchi wrote:
early_pci_scan_bus() does a depth-first traversal, possibly calling the quirk functions for each device based on vendor, device and class from early_qrk table. intel_graphics_quirks() however uses PCI_ANY_ID and does additional filtering in the quirk.
If there is an Intel integrated + discrete GPU the quirk may be called first for the discrete GPU based on the PCI topology. Then we will fail to reserve the system stolen memory for the integrated GPU, because we will already have marked the quirk as "applied".
Who is "we"?
Please use passive voice in your commit message: no "we" or "I", etc, and describe your changes in imperative mood.
Bottom line is: personal pronouns are ambiguous in text, especially with so many parties/companies/etc developing the kernel so let's avoid them please.
I had the impression the subject/title should be imperative, with it more relaxed in the body. It seems we have one more difference among subsystems and I will adapt on next submissions to x86.
To clarify, "we" here means whoever is reading and following the code path. It has the same connotation as the others in 'git log --grep "we\s"'. From a quick grep it seems Linus merges a lot of pull requests using that language and he himself uses it in commit messages. Example: commit 054aa8d439b9 ("fget: check that the fd still exists after getting a ref to it"). I was also surprised he also uses it in the first person in some commits.
This was reproduced in a setup with Alderlake-P (integrated) + DG2 (discrete), with the following PCI topology:
- 00:01.0 Bridge `- 03:00.0 DG2
- 00:02.0 Integrated GPU
So, stop using the QFLAG_APPLY_ONCE flag, replacing it with a static local variable. We can set this variable in the right place, inside intel_graphics_quirks(), only when the quirk was actually applied, i.e. when we find the integrated GPU based on the intel_early_ids table.
Cc: stable@vger.kernel.org Signed-off-by: Lucas De Marchi lucas.demarchi@intel.com
v5: apply fix before the refactor
arch/x86/kernel/early-quirks.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/early-quirks.c b/arch/x86/kernel/early-quirks.c index 1ca3a56fdc2d..de9a76eb544e 100644 --- a/arch/x86/kernel/early-quirks.c +++ b/arch/x86/kernel/early-quirks.c @@ -589,10 +589,14 @@ intel_graphics_stolen(int num, int slot, int func,
static void __init intel_graphics_quirks(int num, int slot, int func) {
static bool quirk_applied __initdata; const struct intel_early_ops *early_ops; u16 device; int i;
if (quirk_applied)
return;device = read_pci_config_16(num, slot, func, PCI_DEVICE_ID);
for (i = 0; i < ARRAY_SIZE(intel_early_ids); i++) {
@@ -605,6 +609,8 @@ static void __init intel_graphics_quirks(int num, int slot, int func)
intel_graphics_stolen(num, slot, func, early_ops);
quirk_applied = true;- return; }
So I wonder: why can't you simply pass in a static struct chipset * pointer into the early_qrk[i].f function and in there you can set QFLAG_APPLIED or so, so that you can mark that the quirk is applied by using the nice, per-quirk flags someone has already added instead of this ugly static variable?
It seems you prefer v1. See 20211218061313.100571-1-lucas.demarchi@intel.com
Although in the review Bjorn suggested just splitting the commit, it was also mentioned that the PCI subsystem has no such logic in its equivalent pci_do_fixups(): a quirk/fixup needing that should instead use a static local.
After checking the code again I seconded his suggestion and adapted on subsequent versions. Besides his comment on PCI subsystem I had these motivations:
1) From a total o 11 quirks, only 3 were actually using that logic and 1 of them was wrong (the one being fixed here with the called vs applied logic)
2) The resources these conditions are protecting are global to the system: they all end up setting a variable - just having a static local protecting the function from being called more than once seemed appropriate to avoid that.
3) Even arch/x86 uses that for the PCI fixups (arch/x86/kernel/quirks.c). It uses the logic "resource has already been set" as opposed to adding static local since, but it seems similar approach to me.
Patch 3 especially makes me go, huh?
What is special about patch 3? Maybe the way it was split in v5 vs v4 made it not so clear: intention was not to change the current behavior since it has been like this for 15+ years with no bug that I know of. The previous approach would not call acpi_table_parse() twice for example.
thanks Lucas De Marchi
-- Regards/Gruss, Boris.