From: David Woodhouse Date: Tue, 21 Mar 2023 12:47:52 +0000 (+0100) Subject: libacpi: fix PCI hotplug AML X-Git-Tag: archive/raspbian/4.17.1+2-gb773c48e36-1+rpi1~1^2~30^2 X-Git-Url: https://dgit.raspbian.org/%22http://www.example.com/cgi/%22/%22http:/www.example.com/cgi/%22?a=commitdiff_plain;h=3eac216e6e60860bbc030602c401d3ef8efce8d9;p=xen.git libacpi: fix PCI hotplug AML The emulated PIIX3 uses a nybble for the status of each PCI function, so the status for e.g. slot 0 functions 0 and 1 respectively can be read as (\_GPE.PH00 & 0x0F), and (\_GPE.PH00 >> 0x04). The AML that Xen gives to a guest gets the operand order for the odd- numbered functions the wrong way round, returning (0x04 >> \_GPE.PH00) instead. As far as I can tell, this was the wrong way round in Xen from the moment that PCI hotplug was first introduced in commit 83d82e6f35a8: + ShiftRight (0x4, \_GPE.PH00, Local1) + Return (Local1) /* IN status as the _STA */ Or maybe there's bizarre AML operand ordering going on there, like Intel's wrong-way-round assembler, and it only broke later when it was changed to being generated? Either way, it's definitely wrong now, and instrumenting a Linux guest shows that it correctly sees _STA being 0x00 in function 0 of an empty slot, but then the loop in acpiphp_glue.c::get_slot_status() goes on to look at function 1 and sees that _STA evaluates to 0x04. Thus reporting an adapter is present in every slot in /sys/bus/pci/slots/* Quite why Linux wants to look for function 1 being physically present when function 0 isn't... I don't want to think about right now. Fixes: 83d82e6f35a8 ("hvmloader: pass-through: multi-function PCI hot-plug") Signed-off-by: David Woodhouse Reviewed-by: Jan Beulich master commit: b190af7d3e90f58da5f58044b8dea7261b8b483d master date: 2023-03-20 17:12:34 +0100 --- diff --git a/tools/libacpi/mk_dsdt.c b/tools/libacpi/mk_dsdt.c index 1176da80ef..1d27809116 100644 --- a/tools/libacpi/mk_dsdt.c +++ b/tools/libacpi/mk_dsdt.c @@ -431,7 +431,7 @@ int main(int argc, char **argv) stmt("Store", "0x89, \\_GPE.DPT2"); } if ( slot & 1 ) - stmt("ShiftRight", "0x4, \\_GPE.PH%02X, Local1", slot & ~1); + stmt("ShiftRight", "\\_GPE.PH%02X, 0x04, Local1", slot & ~1); else stmt("And", "\\_GPE.PH%02X, 0x0f, Local1", slot & ~1); stmt("Return", "Local1"); /* IN status as the _STA */