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From: James Morse <james.morse@arm.com>
To: Marc Zyngier <maz@kernel.org>,
	kexec@lists.infradead.org, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.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 <bhupesh.sharma@linaro.org>,
	AKASHI Takahiro <takahiro.akashi@linaro.org>,
	Dave Young <dyoung@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Moritz Fischer <mdf@kernel.org>,
	kernel-team@android.com, stable@vger.kernel.org
Subject: Re: [PATCH v2 1/5] arm64: kexec_file: Forbid non-crash kernels
Date: Fri, 4 Jun 2021 17:20:36 +0100	[thread overview]
Message-ID: <e1d3bd1a-3935-d14b-9d2a-183ec4758665@arm.com> (raw)
In-Reply-To: <20210531095720.77469-2-maz@kernel.org>

On 31/05/2021 10:57, Marc Zyngier wrote:
> It has been reported that kexec_file doesn't really work on arm64.
> It completely ignores any of the existing reservations, which results
> in the secondary kernel being loaded where the GICv3 LPI tables live,


> or even corrupting the ACPI tables.

I'd like to know how the ACPI tables bit happens.

ACPI tables should be in EFI_ACPI_RECLAIM_MEMORY or EFI_ACPI_MEMORY_NVS (which isn't
treated as usable).

EFI's reserve_regions() does this:
|	if (!is_usable_memory(md))
|		memblock_mark_nomap(paddr, size);
|
|	/* keep ACPI reclaim memory intact for kexec etc. */
|	if (md->type == EFI_ACPI_RECLAIM_MEMORY)
|		memblock_reserve(paddr, size);

which is called via efi_init(), and all those regions end up listed as reserved in
/proc/iomem. (this is why arm64 doesn't call acpi_reserve_initial_tables())

If your firmware puts ACPI tables are in EFI_CONVENTIONAL_MEMORY, you have bigger problems
as the kernel could get relocated over the top of them during boot, and even if it
doesn't, nothing stops that  memory being allocated for user-space.

Even acpi_table_upgrade() calls memblock_reserve() and happens early enough not to be a
problem.


Please share ... enjoyment, optional.

(boot with efi=debug and post the EFI memory map and the 'ACPI: FOO 0xphysicaladdress'
stuff at the top of the boot log)


Thanks,

James


> Since only crash kernels are imune to this as they use a reserved
> memory region, disable the non-crash kernel use case. Further
> patches will try and restore the functionality.

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  parent reply	other threads:[~2021-06-04 16:22 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-31  9:57 [PATCH v2 0/5] arm64: Make kexec_file_load honor iomem reservations Marc Zyngier
2021-05-31  9:57 ` [PATCH v2 1/5] arm64: kexec_file: Forbid non-crash kernels Marc Zyngier
2021-05-31 19:37   ` Ard Biesheuvel
2021-06-01  8:36     ` Marc Zyngier
2021-06-04 16:20   ` James Morse [this message]
2021-05-31  9:57 ` [PATCH v2 2/5] kexec_file: Make locate_mem_hole_callback global Marc Zyngier
2021-05-31  9:57 ` [PATCH v2 3/5] kernel/resource: Allow find_next_iomem_res() to exclude overlapping child resources Marc Zyngier
2021-05-31  9:57 ` [PATCH v2 4/5] kernel/resource: Introduce walk_system_ram_excluding_child_res() Marc Zyngier
2021-05-31  9:57 ` [PATCH v2 5/5] arm64: kexec_image: Restore full kexec functionnality Marc Zyngier
2021-05-31 19:36 ` [PATCH v2 0/5] arm64: Make kexec_file_load honor iomem reservations Ard Biesheuvel
2021-06-04 16:20 ` James Morse
2021-06-09 22:39   ` Moritz Fischer

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