linux-kernel - Re: [PATCH v7 1/8] mm/memblock: Tag memblocks with crypto capabilities

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Date:   Tue, 26 Apr 2022 16:20:55 +0300
From:   Mike Rapoport <rppt@...nel.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,
        akpm@...ux-foundation.org, daniel.gutson@...ypsium.com,
        hughsient@...il.com, alex.bazhaniuk@...ypsium.com,
        alison.schofield@...el.com, keescook@...omium.org
Subject: Re: [PATCH v7 1/8] mm/memblock: Tag memblocks with crypto
 capabilities

On Tue, Apr 26, 2022 at 09:59:04AM -0300, Martin Fernandez wrote:
> On 4/26/22, Mike Rapoport <rppt@...nel.org> wrote:
> > On Mon, Apr 25, 2022 at 02:15:19PM -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 |  5 ++++
> >>  mm/memblock.c            | 62 ++++++++++++++++++++++++++++++++++++++++
> >>  2 files changed, 67 insertions(+)
> >>
> >> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> >> index 50ad19662a32..00c4f1a20335 100644
> >> --- a/include/linux/memblock.h
> >> +++ b/include/linux/memblock.h
> >> @@ -40,6 +40,7 @@ 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 */
> >> @@ -47,6 +48,7 @@ enum memblock_flags {
> >>  	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 */
> >>  };
> >>
> >>  /**
> >> @@ -120,6 +122,9 @@ 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 e4f03a6e8e56..fe62f81572e6 100644
> >> --- a/mm/memblock.c
> >> +++ b/mm/memblock.c
> >> @@ -191,6 +191,40 @@ 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
> >
> > I'd s/in memory memblock_type/in @nid
> >
> 
> Good, thanks.
> 
> >> + * encryption, false otherwise.
> >> + */
> >> +bool __init_memblock memblock_node_is_crypto_capable(int nid)
> >> +{
> >> +	struct memblock_region *region;
> >> +	int crypto_capables = 0;
> >> +	int not_crypto_capables = 0;
> >> +
> >> +	for_each_mem_region(region) {
> >> +		if (memblock_get_region_node(region) == nid) {
> >> +			if (region->flags & MEMBLOCK_CRYPTO_CAPABLE)
> >> +				crypto_capables++;
> >> +			else
> >> +				not_crypto_capables++;
> >> +		}
> >> +	}
> >> +
> >> +	if (crypto_capables > 0 && not_crypto_capables > 0)
> >> +		pr_warn("Node %d has %d regions that are encryptable and %d regions
> >> that aren't",
> >> +			nid, not_crypto_capables, crypto_capables);
> >> +
> >> +	return not_crypto_capables == 0;
> >
> > This will return true for memoryless nodes as well. Do you mean to consider
> > them as capable of encryption?
> >
> 
> Not really, I didn't think about that to be honest. I don't think it's
> a good idea to consider them as capable, right?

I think capable of encryption would mean

	crypto_capables && !not_crypto_capables 

-- 
Sincerely yours,
Mike.