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From: Vlastimil Babka <vbabka@suse.cz>
To: Mike Rapoport <rppt@kernel.org>,
	"Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"peterz@infradead.org" <peterz@infradead.org>,
	"keescook@chromium.org" <keescook@chromium.org>,
	"Weiny, Ira" <ira.weiny@intel.com>,
	"linux-hardening@vger.kernel.org"
	<linux-hardening@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"x86@kernel.org" <x86@kernel.org>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
	"Williams, Dan J" <dan.j.williams@intel.com>,
	"Lutomirski, Andy" <luto@kernel.org>,
	"kernel-hardening@lists.openwall.com" 
	<kernel-hardening@lists.openwall.com>,
	"Hansen, Dave" <dave.hansen@intel.com>,
	"shakeelb@google.com" <shakeelb@google.com>
Subject: Re: [RFC PATCH v2 11/19] mm/sparsemem: Use alloc_table() for table allocations
Date: Thu, 2 Sep 2021 15:56:55 +0200	[thread overview]
Message-ID: <38d2a358-4146-bfc9-2a4f-68ce02f75c94@suse.cz> (raw)
In-Reply-To: <YS8qRHrGzevns32P@kernel.org>

On 9/1/21 09:22, Mike Rapoport wrote:
> On Tue, Aug 31, 2021 at 06:25:23PM +0000, Edgecombe, Rick P wrote:
>> On Tue, 2021-08-31 at 11:55 +0300, Mike Rapoport wrote:
>> > On Mon, Aug 30, 2021 at 04:59:19PM -0700, Rick Edgecombe wrote:
>> <trim> 
>> > > -static void * __meminit vmemmap_alloc_block_zero(unsigned long
>> > > size, int node)
>> > > +static void * __meminit vmemmap_alloc_table(int node)
>> > >  {
>> > > -	void *p = vmemmap_alloc_block(size, node);
>> > > +	void *p;
>> > > +	if (slab_is_available()) {
>> > > +		struct page *page = alloc_table_node(GFP_KERNEL |
>> > > __GFP_ZERO, node);
>> > 
>> > This change removes __GFP_RETRY_MAYFAIL|__GFP_NOWARN from the
>> > original gfp
>> > vmemmap_alloc_block() used.
>> Oh, yea good point. Hmm, I guess grouped pages could be aware of that
>> flag too. Would be a small addition, but it starts to grow
>> unfortunately.
>> 
>> > Not sure __GFP_RETRY_MAYFAIL is really needed in
>> > vmemmap_alloc_block_zero()
>> > at the first place, though.
>> Looks like due to a real issue:
>> 055e4fd96e95b0eee0d92fd54a26be7f0d3bcad0

That commit added __GFP_REPEAT, but __GFP_RETRY_MAYFAIL these days became
subtly different.

> I believe the issue was with memory map blocks rather than with page
> tables, but since sparse-vmemmap uses the same vmemmap_alloc_block() for
> both, the GFP flag got stick with both.
> 
> I'm not really familiar with reclaim internals to say if
> __GFP_RETRY_MAYFAIL would help much for order-0 allocation.

For costly allocation, __GFP_RETRY_MAYFAIL will try harder, thus the RETRY
part is accented. For order-0 the only difference is that it will skip OOM,
thus the MAYFAIL part. It usually means there's a fallback. I guess in this
case there's no fallback, so allocating without __GFP_RETRY_MAYFAIL would be
better.

> Vlastimil, can you comment on this?
>  
>> I think it should not affect PKS tables for now, so maybe I can make
>> separate logic instead. I'll look into it. Thanks.
>> > 
>> > More broadly, maybe it makes sense to split boot time and memory
>> > hotplug
>> > paths and use pxd_alloc() for the latter.
>> > 
>> > > +
>> > > +		if (!page)
>> > > +			return NULL;
>> > > +		return page_address(page);
>> > > +	}
>> > >  
>> > > +	p = __earlyonly_bootmem_alloc(node, PAGE_SIZE, PAGE_SIZE,
>> > > __pa(MAX_DMA_ADDRESS));
>> > 
>> > Opportunistically rename to __earlyonly_memblock_alloc()? ;-)
>> > 
>> Heh, I can. Just grepping, there are several other instances of
>> foo_bootmem() only calling foo_memblock() pattern scattered about. Or
>> maybe I'm missing the distinction.
> 
> Heh, I didn't do s/bootmem/memblock/g, so foo_bootmem() are reminders we
> had bootmem allocator once.
> Maybe it's a good time to remove them :)
>  
>> <trim>
> 


  reply	other threads:[~2021-09-02 13:57 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-30 23:59 [RFC PATCH v2 00/19] PKS write protected page tables Rick Edgecombe
2021-08-30 23:59 ` [RFC PATCH v2 01/19] list: Support getting most recent element in list_lru Rick Edgecombe
2021-08-30 23:59 ` [RFC PATCH v2 02/19] list: Support list head not in object for list_lru Rick Edgecombe
2021-08-30 23:59 ` [RFC PATCH v2 03/19] x86/mm/cpa: Add grouped page allocations Rick Edgecombe
2021-08-30 23:59 ` [RFC PATCH v2 04/19] mm: Explicitly zero page table lock ptr Rick Edgecombe
2021-08-30 23:59 ` [RFC PATCH v2 05/19] x86, mm: Use cache of page tables Rick Edgecombe
2021-08-31  8:40   ` Mike Rapoport
2021-08-31 19:09     ` Edgecombe, Rick P
2021-08-30 23:59 ` [RFC PATCH v2 06/19] x86/mm/cpa: Add perm callbacks to grouped pages Rick Edgecombe
2021-08-30 23:59 ` [RFC PATCH v2 07/19] x86/cpufeatures: Add feature for pks tables Rick Edgecombe
2021-08-30 23:59 ` [RFC PATCH v2 08/19] x86/mm/cpa: Add get_grouped_page_atomic() Rick Edgecombe
2021-08-30 23:59 ` [RFC PATCH v2 09/19] x86/mm: Support GFP_ATOMIC in alloc_table_node() Rick Edgecombe
2021-08-31  8:32   ` Mike Rapoport
2021-08-30 23:59 ` [RFC PATCH v2 10/19] x86/mm: Use alloc_table() for fill_pte(), etc Rick Edgecombe
2021-08-31  8:47   ` Mike Rapoport
2021-08-31 18:48     ` Edgecombe, Rick P
2021-08-30 23:59 ` [RFC PATCH v2 11/19] mm/sparsemem: Use alloc_table() for table allocations Rick Edgecombe
2021-08-31  8:55   ` Mike Rapoport
2021-08-31 18:25     ` Edgecombe, Rick P
2021-09-01  7:22       ` Mike Rapoport
2021-09-02 13:56         ` Vlastimil Babka [this message]
2021-08-30 23:59 ` [RFC PATCH v2 12/19] x86/mm: Use free_table in unmap path Rick Edgecombe
2021-08-30 23:59 ` [RFC PATCH v2 13/19] mm/debug_vm_page_table: Use setters instead of WRITE_ONCE Rick Edgecombe
2021-08-30 23:59 ` [RFC PATCH v2 14/19] x86/efi: Toggle table protections when copying Rick Edgecombe
2021-08-30 23:59 ` [RFC PATCH v2 15/19] x86/mm/cpa: Add set_memory_pks() Rick Edgecombe
2021-08-30 23:59 ` [RFC PATCH v2 16/19] x86/mm: Protect page tables with PKS Rick Edgecombe
2021-08-31  8:56   ` Mike Rapoport
2021-08-31 17:55     ` Edgecombe, Rick P
2021-08-30 23:59 ` [RFC PATCH v2 17/19] x86/mm/cpa: PKS protect direct map page tables Rick Edgecombe
2021-08-31 10:14   ` Mike Rapoport
2021-08-31 17:58     ` Edgecombe, Rick P
2021-08-30 23:59 ` [RFC PATCH v2 18/19] x86/mm: Add PKS table soft mode Rick Edgecombe
2021-08-31  3:49   ` Randy Dunlap
2021-08-31 17:55     ` Edgecombe, Rick P
2021-08-30 23:59 ` [RFC PATCH v2 19/19] x86/mm: Add PKS table debug checking Rick Edgecombe

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