Re: [PATCH v3 3/5] mm/memory-failure: efi: record hardware-poisoned frames into the poisoned-memory table

[Kiryl Shutsemau <kas@kernel.org>]

On Wed, Aug 26, 2026 at 05:03:54AM -0700, Breno Leitao wrote:
> diff --git a/drivers/firmware/efi/poison.c b/drivers/firmware/efi/poison.c
> new file mode 100644
> index 0000000000000..d6855e712832c
> --- /dev/null
> +++ b/drivers/firmware/efi/poison.c
> @@ -0,0 +1,126 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Runtime side of the LINUX_EFI_POISONED_MEMORY table: one bit per
> + * EFI_POISON_UNIT_SIZE, set here as frames go bad, honored by the next kernel.
> + *
> + * Copyright (c) 2026 Meta Platforms, Inc. and affiliates.
> + * Copyright (c) 2026 Breno Leitao <leitao@debian.org>
> + */
> +
> +#define pr_fmt(fmt) "efi: " fmt
> +
> +#include <linux/bitmap.h>
> +#include <linux/efi.h>
> +#include <linux/io.h>
> +#include <linux/log2.h>
> +#include <linux/memblock.h>

Is it leftover? I don't see any memblock usage.

> +#include <linux/mm.h>
> +#include <linux/overflow.h>
> +
> +static struct linux_efi_poisoned_memory *efi_poison __ro_after_init;
> +static u64 efi_poison_nbits __ro_after_init;
> +
> +static u64 __init
> +efi_poison_usable_size(const struct linux_efi_poisoned_memory *pm)
> +{
> +	u64 nr_units = DIV_ROUND_UP(PFN_PHYS(max_pfn), pm->unit_size);
> +	u64 bytes = DIV_ROUND_UP(nr_units, BITS_PER_BYTE);
> +
> +	/* Whole words: the bitmap is reached an unsigned long at a time. */
> +	return min(round_up(bytes, sizeof(unsigned long)), pm->size);

Hm. Why bother to clamp to max_pfn? What's what's wrong with just using
pm->size directly?

> +}
> +

-- 
  Kiryl Shutsemau / Kirill A. Shutemov