On Tue, Nov 29, 2016 at 11:21 PM, Lv Zheng <lv.zheng@xxxxxxxxx> wrote: > ACPICA commit cac6790954d4d752a083e6122220b8a22febcd07 > > This patch back ports Linux acpi_get_table_with_size() and > early_acpi_os_unmap_memory() into ACPICA upstream to reduce divergences. > > The 2 APIs are used by Linux as table management APIs for long time, it > contains a hidden logic that during the early stage, the mapped tables > should be unmapped before the early stage ends. > > During the early stage, tables are handled by the following sequence: > acpi_get_table_with_size(); > parse the table > early_acpi_os_unmap_memory(); > During the late stage, tables are handled by the following sequence: > acpi_get_table(); > parse the table > Linux uses acpi_gbl_permanent_mmap to distinguish the early stage and the > late stage. > > The reasoning of introducing acpi_get_table_with_size() is: ACPICA will > remember the early mapped pointer in acpi_get_table() and Linux isn't able to > prevent ACPICA from using the wrong early mapped pointer during the late > stage as there is no API provided from ACPICA to be an inverse of > acpi_get_table() to forget the early mapped pointer. > > But how ACPICA can work with the early/late stage requirement? Inside of > ACPICA, tables are ensured to be remained in "INSTALLED" state during the > early stage, and they are carefully not transitioned to "VALIDATED" state > until the late stage. So the same logic is in fact implemented inside of > ACPICA in a different way. The gap is only that the feature is not provided > to the OSPMs in an accessible external API style. > > It then is possible to fix the gap by providing an inverse of > acpi_get_table() from ACPICA, so that the two Linux sequences can be > combined: > acpi_get_table(); > parse the table > acpi_put_table(); > In order to work easier with the current Linux code, acpi_get_table() and > acpi_put_table() is implemented in a usage counting based style: > 1. When the usage count of the table is increased from 0 to 1, table is > mapped and .Pointer is set with the mapping address (VALIDATED); > 2. When the usage count of the table is decreased from 1 to 0, .Pointer > is unset and the mapping address is unmapped (INVALIDATED). > So that we can deploy the new APIs to Linux with minimal effort by just > invoking acpi_get_table() in acpi_get_table_with_size() and invoking > acpi_put_table() in early_acpi_os_unmap_memory(). Lv Zheng. > > Link: https://github.com/acpica/acpica/commit/cac67909 > Signed-off-by: Lv Zheng <lv.zheng@xxxxxxxxx> > Signed-off-by: Bob Moore <robert.moore@xxxxxxxxx> This commit in -next (071b39575679 ACPICA: Tables: Back port acpi_get_table_with_size() and early_acpi_os_unmap_memory() from Linux kernel) causes a regression in my nfit/nvdimm test environment. The nfit produced by QEMU no longer results in a nvdimm bus being created. I have not root caused it, but I'm using the following command line options to create an nfit in qemu-2.6. Reverting the commit leads compile failures. qemu=$HOME/git/qemu/build/x86_64-softmmu/qemu-system-x86_64 mem=$HOME/mem label_size=$((128*1024)) mem_size=$(((3*1024*1024*1024) + (64 * 1024 *1024))) IMAGE=$HOME/ahci.img kvm=( $qemu -enable-kvm -cpu kvm64 -kernel $kernel -initrd $initrd -m 12G,slots=3,maxmem=40G -machine pc-i440fx-2.4,accel=kvm,usb=off,vmport=off,nvdimm -cpu SandyBridge -smp 2 -netdev tap,id=hostnet0,ifname=tap0,script=no,downscript=no -device virtio-net-pci,netdev=hostnet0,id=net0,mac=52:54:00:b7:a1:ad,bus=pci.0,addr=0x7 -object memory-backend-file,id=mem1,share,mem-path=${mem},size=$((label_size + mem_size)) -device nvdimm,memdev=mem1,id=nv1,label-size=${label_size} -device ahci,id=sata0,bus=pci.0,addr=0x8 -drive file=$IMAGE,if=none,id=drive-sata0-0-0,format=raw -device ide-hd,bus=sata0.0,drive=drive-sata0-0-0,id=sata0-0-0 -boot order=nc -no-reboot -watchdog i6300esb -rtc base=localtime -serial stdio -display none -monitor null ) -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
