Re: [RFT 1/2] RISC-V: handle missing "no-map" properties for OpenSBI's PMP protected regions
From: Atish Kumar Patra
Date: Tue Aug 08 2023 - 15:52:52 EST
On Wed, Aug 2, 2023 at 4:14 AM Conor Dooley <conor.dooley@xxxxxxxxxxxxx> wrote:
>
> Add an erratum for versions [v0.8 to v1.3) of OpenSBI which fail to add
> the "no-map" property to the reserved memory nodes for the regions it
> has protected using PMPs.
>
> Our existing fix sweeping hibernation under the carpet by marking it
> NONPORTABLE is insufficient as there are other ways to generate
> accesses to these reserved memory regions, as Petr discovered [1]
> while testing crash kernels & kdump.
>
> Intercede during the boot process when the afflicted versions of OpenSBI
> are present & set the "no-map" property in all "mmode_resv" nodes before
> the kernel does its reserved memory region initialisation.
>
We have different mechanisms of DT being passed to the kernel.
1. A prior stage(e.g U-Boot SPL) to M-mode runtime firmware (e.g.
OpenSBI, rustSBI) passes the DT to M-mode runtime firmware and it
passes to the next stage.
In this case, M-mode runtime firmware gets a chance to update the
no-map property in DT that the kernel can parse.
2. User loads the DT from the boot loader (e.g EDK2, U-Boot proper).
Any DT patching done by the M-mode firmware is useless. If these DTBs
don't have the no-map
property, hibernation or EFI booting will have issues as well.
We are trying to solve only one part of problem #1 in this patch. I
don't think any other M-mode runtime firmware patches DT with no-map
property as well.
Please let me know if I am wrong about that. The problem is not
restricted to [v0.8 to v1.3) of OpenSBI.
The booting doc now says that no-map property must be set and any
usage of DTBs without that (via #1 or #2) will have unintended
consequences.
> Reported-by: Song Shuai <suagrfillet@xxxxxxxxx>
> Link: https://lore.kernel.org/all/CAAYs2=gQvkhTeioMmqRDVGjdtNF_vhB+vm_1dHJxPNi75YDQ_Q@xxxxxxxxxxxxxx/
> Reported-by: JeeHeng Sia <jeeheng.sia@xxxxxxxxxxxxxxxx>
> Link: https://groups.google.com/a/groups.riscv.org/g/sw-dev/c/ITXwaKfA6z8
> Reported-by: Petr Tesarik <petrtesarik@xxxxxxxxxxxxxxx>
> Closes: https://lore.kernel.org/linux-riscv/76ff0f51-d6c1-580d-f943-061e93073306@xxxxxxxxxxxxxxx/ [1]
> CC: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
> ---
> arch/riscv/include/asm/sbi.h | 5 +++++
> arch/riscv/kernel/sbi.c | 42 +++++++++++++++++++++++++++++++++++-
> arch/riscv/mm/init.c | 3 +++
> 3 files changed, 49 insertions(+), 1 deletion(-)
>
> diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
> index 5b4a1bf5f439..5360f3476278 100644
> --- a/arch/riscv/include/asm/sbi.h
> +++ b/arch/riscv/include/asm/sbi.h
> @@ -252,6 +252,9 @@ enum sbi_pmu_ctr_type {
> #define SBI_ERR_ALREADY_STARTED -7
> #define SBI_ERR_ALREADY_STOPPED -8
>
> +/* SBI implementation IDs */
> +#define SBI_IMP_OPENSBI 1
> +
> extern unsigned long sbi_spec_version;
> struct sbiret {
> long error;
> @@ -259,6 +262,8 @@ struct sbiret {
> };
>
> void sbi_init(void);
> +void sbi_apply_reserved_mem_erratum(void *dtb_va);
> +
> struct sbiret sbi_ecall(int ext, int fid, unsigned long arg0,
> unsigned long arg1, unsigned long arg2,
> unsigned long arg3, unsigned long arg4,
> diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c
> index c672c8ba9a2a..aeb27263fa53 100644
> --- a/arch/riscv/kernel/sbi.c
> +++ b/arch/riscv/kernel/sbi.c
> @@ -5,8 +5,10 @@
> * Copyright (c) 2020 Western Digital Corporation or its affiliates.
> */
>
> +#include <linux/acpi.h>
> #include <linux/bits.h>
> #include <linux/init.h>
> +#include <linux/libfdt.h>
> #include <linux/pm.h>
> #include <linux/reboot.h>
> #include <asm/sbi.h>
> @@ -583,6 +585,40 @@ long sbi_get_mimpid(void)
> }
> EXPORT_SYMBOL_GPL(sbi_get_mimpid);
>
> +static long sbi_firmware_id;
> +static long sbi_firmware_version;
> +
> +/*
> + * For devicetrees patched by OpenSBI a "mmode_resv" node is added to cover
> + * the region OpenSBI has protected by means of a PMP. Some versions of OpenSBI,
> + * [v0.8 to v1.3), omitted the "no-map" property, but this trips up hibernation
> + * among other things.
> + */
> +void __init sbi_apply_reserved_mem_erratum(void *dtb_pa)
> +{
> + int child, reserved_mem;
> +
> + if (sbi_firmware_id != SBI_IMP_OPENSBI)
> + return;
> +
> + if (!acpi_disabled)
> + return;
> +
> + if (sbi_firmware_version >= 0x10003 || sbi_firmware_version < 0x8)
> + return;
> +
> + reserved_mem = fdt_path_offset((void *)dtb_pa, "/reserved-memory");
> + if (reserved_mem < 0)
> + return;
> +
> + fdt_for_each_subnode(child, (void *)dtb_pa, reserved_mem) {
> + const char *name = fdt_get_name((void *)dtb_pa, child, NULL);
> +
> + if (!strncmp(name, "mmode_resv", 10))
> + fdt_setprop((void *)dtb_pa, child, "no-map", NULL, 0);
> + }
> +};
> +
> void __init sbi_init(void)
> {
> int ret;
> @@ -596,8 +632,12 @@ void __init sbi_init(void)
> sbi_major_version(), sbi_minor_version());
>
> if (!sbi_spec_is_0_1()) {
> + sbi_firmware_id = sbi_get_firmware_id();
> + sbi_firmware_version = sbi_get_firmware_version();
> +
> pr_info("SBI implementation ID=0x%lx Version=0x%lx\n",
> - sbi_get_firmware_id(), sbi_get_firmware_version());
> + sbi_firmware_id, sbi_firmware_version);
> +
> if (sbi_probe_extension(SBI_EXT_TIME)) {
> __sbi_set_timer = __sbi_set_timer_v02;
> pr_info("SBI TIME extension detected\n");
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 70fb31960b63..cb16bfdeacdb 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -29,6 +29,7 @@
> #include <asm/tlbflush.h>
> #include <asm/sections.h>
> #include <asm/soc.h>
> +#include <asm/sbi.h>
> #include <asm/io.h>
> #include <asm/ptdump.h>
> #include <asm/numa.h>
> @@ -253,6 +254,8 @@ static void __init setup_bootmem(void)
> * in the device tree, otherwise the allocation could end up in a
> * reserved region.
> */
> +
> + sbi_apply_reserved_mem_erratum(dtb_early_va);
> early_init_fdt_scan_reserved_mem();
>
> /*
> --
> 2.40.1
>