From: James Morse <james.morse@arm.com> To: Marc Zyngier <maz@kernel.org>, kexec@lists.infradead.org, linux-arm-kernel@lists.infradead.org Cc: Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>, Ard Biesheuvel <ardb@kernel.org>, Mark Rutland <mark.rutland@arm.com>, Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>, Hanjun Guo <guohanjun@huawei.com>, Sudeep Holla <sudeep.holla@arm.com>, Eric Biederman <ebiederm@xmission.com>, Bhupesh Sharma <bhsharma@redhat.com>, AKASHI Takahiro <takahiro.akashi@linaro.org>, kernel-team@android.com Subject: Re: [PATCH 0/2] arm64: kexec_file_load vs memory reservations Date: Wed, 2 Jun 2021 15:22:00 +0100 [thread overview] Message-ID: <edb33645-864f-6a2d-ce57-c542f8b79209@arm.com> (raw) In-Reply-To: <20210429133533.1750721-1-maz@kernel.org> Hi Marc, On 29/04/2021 14:35, Marc Zyngier wrote: > It recently became apparent that using kexec with kexec_file_load() on > arm64 is pretty similar to playing Russian roulette. > > Depending on the amount of memory, the HW supported and the firmware > interface used, your secondary kernel may overwrite critical memory > regions without which the secondary kernel cannot boot (the GICv3 LPI > tables being a prime example of such reserved regions). > > It turns out that there is at least two ways for reserved memory > regions to be described to kexec: /proc/iomem for the userspace > implementation, and memblock.reserved for kexec_file. One is spilled into the other by request_standard_resources()... > And of course, > our LPI tables are only reserved using the resource tree, leading to > the aforementioned stamping. Presumably well after efi_init() has run... > Similar things could happen with ACPI tables as well. efi_init() calls reserve_regions(), which has: | /* keep ACPI reclaim memory intact for kexec etc. */ | if (md->type == EFI_ACPI_RECLAIM_MEMORY) | memblock_reserve(paddr, size); This is also what stops mm from allocating them, as memblock-reserved gets copied into the PG_Reserved flag by free_low_memory_core_early()'s calls to reserve_bootmem_region(). Is your machines firmware putting them in a region with a different type? (The UEFI spec has something to say: see 2.3.6 "AArch64 Platforms": | ACPI Tables loaded at boot time can be contained in memory of type EfiACPIReclaimMemory | (recommended) or EfiACPIMemoryNVS NVS would fail the is_usable_memory() check earlier, so gets treated as nomap) Thanks, James > On my 24xA53 system artificially limited to 256MB of RAM (yes, it > boots with that little memory), trying to kexec a secondary kernel > failed every times. I can only presume that this was mostly tested > using kdump, which preserves the entire kernel memory range. > > This small series aims at triggering a discussion on what are the > expectations for kexec_file, and whether we should unify the two > reservation mechanisms. > > And in the meantime, it gets things going... > > Marc Zyngier (2): > firmware/efi: Tell memblock about EFI reservations > ACPI: arm64: Reserve the ACPI tables in memblock > > arch/arm64/kernel/acpi.c | 1 + > drivers/firmware/efi/efi.c | 23 ++++++++++++++++++++++- > 2 files changed, 23 insertions(+), 1 deletion(-) > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
WARNING: multiple messages have this Message-ID (diff)
From: James Morse <james.morse@arm.com> To: Marc Zyngier <maz@kernel.org>, kexec@lists.infradead.org, linux-arm-kernel@lists.infradead.org Cc: Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>, Ard Biesheuvel <ardb@kernel.org>, Mark Rutland <mark.rutland@arm.com>, Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>, Hanjun Guo <guohanjun@huawei.com>, Sudeep Holla <sudeep.holla@arm.com>, Eric Biederman <ebiederm@xmission.com>, Bhupesh Sharma <bhsharma@redhat.com>, AKASHI Takahiro <takahiro.akashi@linaro.org>, kernel-team@android.com Subject: Re: [PATCH 0/2] arm64: kexec_file_load vs memory reservations Date: Wed, 2 Jun 2021 15:22:00 +0100 [thread overview] Message-ID: <edb33645-864f-6a2d-ce57-c542f8b79209@arm.com> (raw) In-Reply-To: <20210429133533.1750721-1-maz@kernel.org> Hi Marc, On 29/04/2021 14:35, Marc Zyngier wrote: > It recently became apparent that using kexec with kexec_file_load() on > arm64 is pretty similar to playing Russian roulette. > > Depending on the amount of memory, the HW supported and the firmware > interface used, your secondary kernel may overwrite critical memory > regions without which the secondary kernel cannot boot (the GICv3 LPI > tables being a prime example of such reserved regions). > > It turns out that there is at least two ways for reserved memory > regions to be described to kexec: /proc/iomem for the userspace > implementation, and memblock.reserved for kexec_file. One is spilled into the other by request_standard_resources()... > And of course, > our LPI tables are only reserved using the resource tree, leading to > the aforementioned stamping. Presumably well after efi_init() has run... > Similar things could happen with ACPI tables as well. efi_init() calls reserve_regions(), which has: | /* keep ACPI reclaim memory intact for kexec etc. */ | if (md->type == EFI_ACPI_RECLAIM_MEMORY) | memblock_reserve(paddr, size); This is also what stops mm from allocating them, as memblock-reserved gets copied into the PG_Reserved flag by free_low_memory_core_early()'s calls to reserve_bootmem_region(). Is your machines firmware putting them in a region with a different type? (The UEFI spec has something to say: see 2.3.6 "AArch64 Platforms": | ACPI Tables loaded at boot time can be contained in memory of type EfiACPIReclaimMemory | (recommended) or EfiACPIMemoryNVS NVS would fail the is_usable_memory() check earlier, so gets treated as nomap) Thanks, James > On my 24xA53 system artificially limited to 256MB of RAM (yes, it > boots with that little memory), trying to kexec a secondary kernel > failed every times. I can only presume that this was mostly tested > using kdump, which preserves the entire kernel memory range. > > This small series aims at triggering a discussion on what are the > expectations for kexec_file, and whether we should unify the two > reservation mechanisms. > > And in the meantime, it gets things going... > > Marc Zyngier (2): > firmware/efi: Tell memblock about EFI reservations > ACPI: arm64: Reserve the ACPI tables in memblock > > arch/arm64/kernel/acpi.c | 1 + > drivers/firmware/efi/efi.c | 23 ++++++++++++++++++++++- > 2 files changed, 23 insertions(+), 1 deletion(-) > _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec
next prev parent reply other threads:[~2021-06-02 14:25 UTC|newest] Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-04-29 13:35 [PATCH 0/2] arm64: kexec_file_load vs memory reservations Marc Zyngier 2021-04-29 13:35 ` Marc Zyngier 2021-04-29 13:35 ` [PATCH 1/2] firmware/efi: Tell memblock about EFI reservations Marc Zyngier 2021-04-29 13:35 ` Marc Zyngier 2021-05-03 18:56 ` Moritz Fischer 2021-05-03 18:56 ` Moritz Fischer 2021-05-13 3:20 ` Dave Young 2021-05-13 3:20 ` Dave Young 2021-05-13 11:11 ` Marc Zyngier 2021-05-13 11:11 ` Marc Zyngier 2021-04-29 13:35 ` [PATCH 2/2] ACPI: arm64: Reserve the ACPI tables in memblock Marc Zyngier 2021-04-29 13:35 ` Marc Zyngier 2021-05-03 18:57 ` Moritz Fischer 2021-05-03 18:57 ` Moritz Fischer 2021-05-12 18:04 ` [PATCH 0/2] arm64: kexec_file_load vs memory reservations Marc Zyngier 2021-05-12 18:04 ` Marc Zyngier 2021-05-13 3:17 ` Dave Young 2021-05-13 3:17 ` Dave Young 2021-05-13 11:07 ` Marc Zyngier 2021-05-13 11:07 ` Marc Zyngier 2021-05-18 11:48 ` Will Deacon 2021-05-18 11:48 ` Will Deacon 2021-05-18 14:23 ` Bhupesh Sharma 2021-05-18 14:23 ` Bhupesh Sharma 2021-05-19 15:19 ` Catalin Marinas 2021-05-19 15:19 ` Catalin Marinas 2021-05-25 16:22 ` Marc Zyngier 2021-05-25 16:22 ` Marc Zyngier 2021-06-02 14:22 ` James Morse [this message] 2021-06-02 14:22 ` James Morse 2021-06-02 15:59 ` Marc Zyngier 2021-06-02 15:59 ` Marc Zyngier 2021-06-02 16:58 ` James Morse 2021-06-02 16:58 ` James Morse
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