linux-kernel - Re: [External] Re: [PATCH v3 0/4] Obtain SMBIOS and ACPI entry from FFI

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAMj1kXEkL0gF8uGcy2AjJvD-yZHmyLX9jiVVDtR+uBAYf+BfUg@mail.gmail.com>
Date:   Sat, 8 Jul 2023 10:45:27 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Dong Wei <Dong.Wei@....com>
Cc:     Conor Dooley <conor@...nel.org>,
        葛士建 <geshijian@...edance.com>,
        Sunil V L <sunilvl@...tanamicro.com>,
        Conor Dooley <conor.dooley@...rochip.com>,
        ron minnich <rminnich@...il.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        "cuiyunhui@...edance.com" <cuiyunhui@...edance.com>,
        "jrtc27@...c27.com" <jrtc27@...c27.com>,
        "kernel@...il.dk" <kernel@...il.dk>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        "aou@...s.berkeley.edu" <aou@...s.berkeley.edu>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
        Mark Rutland <Mark.Rutland@....com>,
        "lpieralisi@...nel.org" <lpieralisi@...nel.org>,
        "rafael@...nel.org" <rafael@...nel.org>,
        "lenb@...nel.org" <lenb@...nel.org>,
        "jdelvare@...e.com" <jdelvare@...e.com>,
        "yc.hung@...iatek.com" <yc.hung@...iatek.com>,
        "angelogioacchino.delregno@...labora.com" 
        <angelogioacchino.delregno@...labora.com>,
        "allen-kh.cheng@...iatek.com" <allen-kh.cheng@...iatek.com>,
        "pierre-louis.bossart@...ux.intel.com" 
        <pierre-louis.bossart@...ux.intel.com>,
        "tinghan.shen@...iatek.com" <tinghan.shen@...iatek.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "weidong.wd@...edance.com" <weidong.wd@...edance.com>
Subject: Re: [External] Re: [PATCH v3 0/4] Obtain SMBIOS and ACPI entry from FFI

On Fri, 7 Jul 2023 at 18:21, Dong Wei <Dong.Wei@....com> wrote:
>
> On Arm systems today, the ACPI RSDP is found using the UEFI Configuration Table. This is true for all Arm SystemReady compliant systems: 1) SystemReady LS: LBBRv1 is using a minimal UEFI FW to load LinuxBoot, that minimal UEFI FW is producing the UEFI Configuration Table. We are working on LBBRv2. LBBRv2 is based on Coreboot loading LinuxBoot. But we do not have a way today to get CoreBoot to produce this pointer to ACPI RSDP. Arm does not support x86 E820 BIOS interface. 2) SystemReady IR: this solution uses DT rather than ACPI. 3) SystemReady ES: this solution can use UBoot or EDK2, and it requires ACPI. Since both UBoot and EDK2 support UEFI now, so ACPI RSDP can be found using the UEFI Configuration Table. 4) SystemReady SR: this solution typically uses EDK2 and requires ACPI, so no issue finding RSDP via UEFI Configuration Table.
>
>
>
> So the ACPI RSDP issue only exist if we want to remove the minimum UEFI FW and go to CoreBoot completely to load LinuxBoot. We are currently exploring how to solve that issue…
>

Hello Dong,

This fixes the RSDP issue perhaps, but that is not the only problem. I
have mentioned this many times already, but let me mention it again
for completeness:

ACPI does not have a memory map, and ARM is much more finicky about
mapping memory regions with the right attributes, given that uncached
accesses don't snoop the caches like they do on x86. This means it is
essential that memory mappings constructed from AML code (which
doesn't provide any context pertaining to the memory type either) are
created with the right memory type.

Currently, the Linux/arm64 glue code for the ACPI core
cross-references every memory mapping created from a SystemMemory
OpRegion by AML code against the EFI memory map, and uses the EFI
memory type and attributes to infer the memory type to program into
the page tables. So simply providing the RSDP is *not* sufficient: on
arm64, more work is needed and currently, booting ACPI without a EFI
memory map results in SystemMemory OpRegions not working at all.

Of course, we might be able to work around that by providing a
'coreboot' memory map for doing ACPI on arm64, but that results in
more fragmentation and an inflated validation matrix, which puts the
burden on the Linux subsystem maintainers to make sure that all these
different combinations remain supported.

AIUI, this memory type issue does not exist for RISC-V today, but I'd
suggest to the RISC-V maintainers to take a careful look at arm64's
acpi_os_ioremap() implementation and decide whether or not RISC-V
needs similar logic.