From: David Hildenbrand <david@redhat.com>
To: Oscar Salvador <osalvador@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
Michal Hocko <mhocko@kernel.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/3] x86/vmemmap: Drop handling of 1GB vmemmap ranges
Date: Wed, 3 Feb 2021 15:12:05 +0100 [thread overview]
Message-ID: <a503f51d-42fe-3cd1-aa7c-66af33f1b3f8@redhat.com> (raw)
In-Reply-To: <20210203141038.GA26693@linux>
On 03.02.21 15:10, Oscar Salvador wrote:
> On Wed, Feb 03, 2021 at 02:33:56PM +0100, David Hildenbrand wrote:
>> One problem I see with existing code / this change making more obvious is
>> that when trying to remove in other granularity than we added (e.g., unplug
>> a 128MB DIMM avaialble during boot), we remove the direct map of unrelated
>> DIMMs.
>
> So, let me see if I understand your concern.
>
> We have a range that was mapped with 1GB page, and we try to remove
> a 128MB chunk from it.
> Yes, in that case we would clear the pud, and that is bad, so we should
> keep the PAGE_ALIGNED checks.
>
> Now, let us assume that scenario.
> If you have a 1GB mapped range and you remove it in smaller chunks bit by bit
> (e.g: 128M), the direct mapping of that range will never be cleared unless
No, that's exactly what's happening. Good thing is that it barely ever
happens, so I assume leaving behind some direct mapping / page tables is
not that bad.
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2021-02-03 14:12 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-03 10:47 [PATCH v2 0/3] Cleanup and fixups for vmemmap handling Oscar Salvador
2021-02-03 10:47 ` [PATCH v2 1/3] x86/vmemmap: Drop handling of 4K unaligned vmemmap range Oscar Salvador
2021-02-03 13:29 ` David Hildenbrand
2021-02-11 21:25 ` Oscar Salvador
2021-02-03 10:47 ` [PATCH v2 2/3] x86/vmemmap: Drop handling of 1GB vmemmap ranges Oscar Salvador
2021-02-03 13:33 ` David Hildenbrand
2021-02-03 14:10 ` Oscar Salvador
2021-02-03 14:12 ` David Hildenbrand [this message]
2021-02-03 14:15 ` Oscar Salvador
2021-02-03 10:47 ` [PATCH v2 3/3] x86/vmemmap: Handle unpopulated sub-pmd ranges Oscar Salvador
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