diff --git a/meta-arm/recipes-kernel/linux/linux-yocto/skip-unavailable-memory.patch b/meta-arm/recipes-kernel/linux/linux-yocto/skip-unavailable-memory.patch index b75cd567..c5dac6aa 100644 --- a/meta-arm/recipes-kernel/linux/linux-yocto/skip-unavailable-memory.patch +++ b/meta-arm/recipes-kernel/linux/linux-yocto/skip-unavailable-memory.patch @@ -1,38 +1,75 @@ -When in secure mode, qemu's devicetree has the following node to mark the -secure memory as off-limits to non-secure environments: +Backported to 5.15. - secram@e000000 { - secure-status = "okay"; - status = "disabled"; - reg = <0x00 0xe000000 0x00 0x1000000>; - device_type = "memory"; - }; - -However, the kernel doesn't think that means the memory is off-limits: - - Early memory node ranges - node 0: [mem 0x000000000e000000-0x000000000e0fffff] - -And not far into the boot accesses this region and crashes: - - Internal error: synchronous external abort: 96000050 15 PREEMPT SMP - -This used to work more through luck than judgement, but recent changes to -memory zoning[1] means this region is accessed more frequently. - -At present there is debate between qemu and kernel engineers over whether -the kernel should be ignoring regions marked like this, or if qemu -should block out the region in a different way. Until this is resolved, -we can make a choice and simply ignore memory ranges that are marked -as disabled. - -Upstream-Status: Pending [discussion ongoing] +Upstream-Status: Submitted [https://lore.kernel.org/linux-arm-kernel/20220517101410.3493781-1-andre.przywara@arm.com/T/#u] Signed-off-by: Ross Burton -[1] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=35ec3d09ff6a49ee90e1bfd09166596f017eb5bb +From 7bfeda1c9224270af97adf799ce0b5a4292bceb6 Mon Sep 17 00:00:00 2001 +From: Andre Przywara +Date: Tue, 17 May 2022 11:14:10 +0100 +Subject: [PATCH] of/fdt: Ignore disabled memory nodes + +When we boot a machine using a devicetree, the generic DT code goes +through all nodes with a 'device_type = "memory"' property, and collects +all memory banks mentioned there. However it does not check for the +status property, so any nodes which are explicitly "disabled" will still +be added as a memblock. +This ends up badly for QEMU, when booting with secure firmware on +arm/arm64 machines, because QEMU adds a node describing secure-only +memory: +=================== + secram@e000000 { + secure-status = "okay"; + status = "disabled"; + reg = <0x00 0xe000000 0x00 0x1000000>; + device_type = "memory"; + }; +=================== + +The kernel will eventually use that memory block (which is located below +the main DRAM bank), but accesses to that will be answered with an +SError: +=================== +[ 0.000000] Internal error: synchronous external abort: 96000050 [#1] PREEMPT SMP +[ 0.000000] Modules linked in: +[ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 5.18.0-rc6-00014-g10c8acb8b679 #524 +[ 0.000000] Hardware name: linux,dummy-virt (DT) +[ 0.000000] pstate: 200000c5 (nzCv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--) +[ 0.000000] pc : new_slab+0x190/0x340 +[ 0.000000] lr : new_slab+0x184/0x340 +[ 0.000000] sp : ffff80000a4b3d10 +.... +================== +The actual crash location and call stack will be somewhat random, and +depend on the specific allocation of that physical memory range. + +As the DT spec[1] explicitly mentions standard properties, add a simple +check to skip over disabled memory nodes, so that we only use memory +that is meant for non-secure code to use. + +That fixes booting a QEMU arm64 VM with EL3 enabled ("secure=on"), when +not using UEFI. In this case the QEMU generated DT will be handed on +to the kernel, which will see the secram node. +This issue is reproducible when using TF-A together with U-Boot as +firmware, then booting with the "booti" command. + +When using U-Boot as an UEFI provider, the code there [2] explicitly +filters for disabled nodes when generating the UEFI memory map, so we +are safe. +EDK/2 only reads the first bank of the first DT memory node [3] to learn +about memory, so we got lucky there. + +[1] https://github.com/devicetree-org/devicetree-specification/blob/main/source/chapter3-devicenodes.rst#memory-node (after the table) +[2] https://source.denx.de/u-boot/u-boot/-/blob/master/lib/fdtdec.c#L1061-1063 +[3] https://github.com/tianocore/edk2/blob/master/ArmVirtPkg/PrePi/FdtParser.c + +Reported-by: Ross Burton +Signed-off-by: Andre Przywara +--- + drivers/of/fdt.c | 3 +++ + 1 file changed, 3 insertions(+) diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c -index 59a7a9ee58ef..d151a31adbf9 100644 +index 59a7a9ee58ef..5439c899fe04 100644 --- a/drivers/of/fdt.c +++ b/drivers/of/fdt.c @@ -1102,6 +1102,9 @@ int __init early_init_dt_scan_memory(unsigned long node, const char *uname, @@ -45,3 +82,5 @@ index 59a7a9ee58ef..d151a31adbf9 100644 reg = of_get_flat_dt_prop(node, "linux,usable-memory", &l); if (reg == NULL) reg = of_get_flat_dt_prop(node, "reg", &l); +-- +2.25.1