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Message-ID: <202202061945.DACC7BD04@keescook>
Date: Mon, 7 Feb 2022 13:18:37 -0800
From: Kees Cook <keescook@...omium.org>
To: Martin Fernandez <martin.fernandez@...ypsium.com>
Cc: linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
platform-driver-x86@...r.kernel.org, linux-mm@...ck.org,
tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
ardb@...nel.org, dvhart@...radead.org, andy@...radead.org,
gregkh@...uxfoundation.org, rafael@...nel.org, rppt@...nel.org,
akpm@...ux-foundation.org, daniel.gutson@...ypsium.com,
hughsient@...il.com, alex.bazhaniuk@...ypsium.com,
alison.schofield@...el.com
Subject: Re: [PATCH v6 1/6] mm/memblock: Tag memblocks with crypto
capabilities
On Thu, Feb 03, 2022 at 01:43:23PM -0300, Martin Fernandez wrote:
> Add the capability to mark regions of the memory memory_type able of
> hardware memory encryption.
>
> Also add the capability to query if all regions of a memory node are
> able to do hardware memory encryption to call it when initializing the
> nodes. Warn the user if a node has both encryptable and
> non-encryptable regions.
>
> Signed-off-by: Martin Fernandez <martin.fernandez@...ypsium.com>
> ---
> include/linux/memblock.h | 15 ++++++----
> mm/memblock.c | 64 ++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 74 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> index 9dc7cb239d21..73edcce165a5 100644
> --- a/include/linux/memblock.h
> +++ b/include/linux/memblock.h
> @@ -41,13 +41,15 @@ extern unsigned long long max_possible_pfn;
> * via a driver, and never indicated in the firmware-provided memory map as
> * system RAM. This corresponds to IORESOURCE_SYSRAM_DRIVER_MANAGED in the
> * kernel resource tree.
> + * @MEMBLOCK_CRYPTO_CAPABLE: capable of hardware encryption
> */
> enum memblock_flags {
> - MEMBLOCK_NONE = 0x0, /* No special request */
> - MEMBLOCK_HOTPLUG = 0x1, /* hotpluggable region */
> - MEMBLOCK_MIRROR = 0x2, /* mirrored region */
> - MEMBLOCK_NOMAP = 0x4, /* don't add to kernel direct mapping */
> - MEMBLOCK_DRIVER_MANAGED = 0x8, /* always detected via a driver */
> + MEMBLOCK_NONE = 0x0, /* No special request */
> + MEMBLOCK_HOTPLUG = 0x1, /* hotpluggable region */
> + MEMBLOCK_MIRROR = 0x2, /* mirrored region */
> + MEMBLOCK_NOMAP = 0x4, /* don't add to kernel direct mapping */
> + MEMBLOCK_DRIVER_MANAGED = 0x8, /* always detected via a driver */
> + MEMBLOCK_CRYPTO_CAPABLE = 0x10, /* capable of hardware encryption */
As already suggested, please keep the tabs like they were. If you're
going to change every line, maybe expand the single-digit literals to 2
digits. (i.e. 0x0 -> 0x00, to keep the most significant bits lined up.)
> };
>
> /**
> @@ -121,6 +123,9 @@ int memblock_physmem_add(phys_addr_t base, phys_addr_t size);
> void memblock_trim_memory(phys_addr_t align);
> bool memblock_overlaps_region(struct memblock_type *type,
> phys_addr_t base, phys_addr_t size);
> +bool memblock_node_is_crypto_capable(int nid);
> +int memblock_mark_crypto_capable(phys_addr_t base, phys_addr_t size);
> +int memblock_clear_crypto_capable(phys_addr_t base, phys_addr_t size);
> int memblock_mark_hotplug(phys_addr_t base, phys_addr_t size);
> int memblock_clear_hotplug(phys_addr_t base, phys_addr_t size);
> int memblock_mark_mirror(phys_addr_t base, phys_addr_t size);
> diff --git a/mm/memblock.c b/mm/memblock.c
> index 1018e50566f3..fcf79befeab3 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -191,6 +191,42 @@ bool __init_memblock memblock_overlaps_region(struct memblock_type *type,
> return i < type->cnt;
> }
>
> +/**
> + * memblock_node_is_crypto_capable - get if whole node is capable
> + * of encryption
> + * @nid: number of node
> + *
> + * Iterate over all memory memblock_type and find if all regions under
> + * node @nid are capable of hardware encryption.
> + *
> + * Return:
> + * true if every region in memory memblock_type is capable of
> + * encryption, false otherwise.
> + */
> +bool __init_memblock memblock_node_is_crypto_capable(int nid)
> +{
> + struct memblock_region *region;
> + bool crypto_capable = false;
> + bool not_crypto_capable = false;
> +
> + for_each_mem_region(region) {
> + if (memblock_get_region_node(region) == nid) {
> + crypto_capable =
> + crypto_capable ||
> + (region->flags & MEMBLOCK_CRYPTO_CAPABLE);
This was already mentioned, but I just thought I'd add: this made me
double-take, given the "||" (instead of "|") in an assignment. It looked
like a typo, but yes it's correct. I was expecting something like:
crypto_capable |=
!!(region->flags & MEMBLOCK_CRYPTO_CAPABLE);
> + not_crypto_capable =
> + not_crypto_capable ||
> + !(region->flags & MEMBLOCK_CRYPTO_CAPABLE);
not_crypto_capable |=
!(region->flags & MEMBLOCK_CRYPTO_CAPABLE);
> + }
> + }
> +
> + if (crypto_capable && not_crypto_capable)
> + pr_warn_once("Node %d has regions that are encryptable and regions that aren't",
> + nid);
> +
> + return !not_crypto_capable;
> +}
> +
> /**
> * __memblock_find_range_bottom_up - find free area utility in bottom-up
> * @start: start of candidate range
> @@ -885,6 +921,34 @@ static int __init_memblock memblock_setclr_flag(phys_addr_t base,
> return 0;
> }
>
> +/**
> + * memblock_mark_crypto_capable - Mark memory regions capable of hardware
> + * encryption with flag MEMBLOCK_CRYPTO_CAPABLE.
> + * @base: the base phys addr of the region
> + * @size: the size of the region
> + *
> + * Return: 0 on success, -errno on failure.
> + */
> +int __init_memblock memblock_mark_crypto_capable(phys_addr_t base,
> + phys_addr_t size)
> +{
> + return memblock_setclr_flag(base, size, 1, MEMBLOCK_CRYPTO_CAPABLE);
> +}
> +
> +/**
> + * memblock_clear_crypto_capable - Clear flag MEMBLOCK_CRYPTO for a
> + * specified region.
> + * @base: the base phys addr of the region
> + * @size: the size of the region
> + *
> + * Return: 0 on success, -errno on failure.
> + */
> +int __init_memblock memblock_clear_crypto_capable(phys_addr_t base,
> + phys_addr_t size)
> +{
> + return memblock_setclr_flag(base, size, 0, MEMBLOCK_CRYPTO_CAPABLE);
> +}
> +
> /**
> * memblock_mark_hotplug - Mark hotpluggable memory with flag MEMBLOCK_HOTPLUG.
> * @base: the base phys addr of the region
> --
> 2.30.2
>
--
Kees Cook
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