From: Dave Hansen <dave.hansen@intel.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>,
Sean Christopherson <seanjc@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Joerg Roedel <jroedel@suse.de>, Andi Kleen <ak@linux.intel.com>,
Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@linux.intel.com>,
David Rientjes <rientjes@google.com>,
Vlastimil Babka <vbabka@suse.cz>,
Tom Lendacky <thomas.lendacky@amd.com>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
Paolo Bonzini <pbonzini@redhat.com>,
Ingo Molnar <mingo@redhat.com>,
Varad Gautam <varad.gautam@suse.com>,
Dario Faggioli <dfaggioli@suse.com>,
x86@kernel.org, linux-mm@kvack.org, linux-coco@lists.linux.dev,
linux-kernel@vger.kernel.org,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCH 2/5] efi/x86: Implement support for unaccepted memory
Date: Thu, 12 Aug 2021 14:43:19 -0700 [thread overview]
Message-ID: <6cf6199c-3c3f-3f36-5570-eadfadb89b30@intel.com> (raw)
In-Reply-To: <20210812211449.5bsblj6lphtu7zsd@box.shutemov.name>
On 8/12/21 2:14 PM, Kirill A. Shutemov wrote:
> On Tue, Aug 10, 2021 at 10:50:33AM -0700, Dave Hansen wrote:
>>> + if ((start & PMD_MASK) == (end & PMD_MASK)) {
>>> + npages = (end - start) / PAGE_SIZE;
>>> + __accept_memory(start, start + npages * PAGE_SIZE);
>>> + return;
>>> + }
>>
>> Hmm, is it possible to have this case hit, but neither of the two below
>> cases? This seems to be looking for a case where the range is somehow
>> entirely contained in one PMD_SIZE area, but where it doesn't consume a
>> whole area.
>>
>> Wouldn't that mean that 'start' or 'end' must be unaligned?
>
> The problem is that if both of them unaligned round_up() and round_down()
> in the cases below would step outside the requested range.
Ahh, got it.
You might want to add some comments like:
/* Immediately accept whole thing if within a PMD_SIZE block: */
/* Immediately accept a <PMD_SIZE piece at the start: */
/* Immediately accept a <PMD_SIZE piece at the end: */
/* Mark full PMD_SIZE areas so they can be accepted later */
To the three if statements and the bitmap_set().
After looking at this, I do think you probably did this the simplest way
possible. It just needs a little help.
>>> + if (start & ~PMD_MASK) {
>>> + npages = (round_up(start, PMD_SIZE) - start) / PAGE_SIZE;
>>> + __accept_memory(start, start + npages * PAGE_SIZE);
>>> + start = round_up(start, PMD_SIZE);
>>> + }
>>> +
>>> + if (end & ~PMD_MASK) {
>>> + npages = (end - round_down(end, PMD_SIZE)) / PAGE_SIZE;
>>> + end = round_down(end, PMD_SIZE);
>>> + __accept_memory(end, end + npages * PAGE_SIZE);
>>> + }
>>> + npages = (end - start) / PMD_SIZE;
>>> + bitmap_set((unsigned long *)params->unaccepted_memory,
>>> + start / PMD_SIZE, npages);
>>> +}
One note as I'm looking at this again: 'npages' can be 0. Imagine if
you had an 8k region that started with the last 4k page of a 2M area and
ended on the first 4k page of the next 2M area, like 0x1ff000->0x201000.
I think it's harmless and bitmap_set() seems to handle it correctly.
But, it's probably worth a comment because it's not obvious.
next prev parent reply other threads:[~2021-08-12 21:43 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-10 6:26 [PATCH 0/5] x86: Impplement support for unaccepted memory Kirill A. Shutemov
2021-08-10 6:26 ` [PATCH 1/5] mm: Add " Kirill A. Shutemov
2021-08-10 7:48 ` David Hildenbrand
2021-08-10 15:02 ` Kirill A. Shutemov
2021-08-10 15:21 ` David Hildenbrand
2021-08-12 20:34 ` Kirill A. Shutemov
2021-08-10 18:13 ` Dave Hansen
2021-08-10 18:30 ` Andi Kleen
2021-08-10 18:56 ` Dave Hansen
2021-08-10 19:23 ` Andi Kleen
2021-08-10 19:46 ` Dave Hansen
2021-08-10 21:20 ` Andi Kleen
2021-08-12 8:19 ` Joerg Roedel
2021-08-12 14:14 ` Dave Hansen
2021-08-12 20:49 ` Kirill A. Shutemov
2021-08-12 20:59 ` Dave Hansen
2021-08-12 21:23 ` Kirill A. Shutemov
2021-08-13 14:49 ` Joerg Roedel
2021-08-17 15:00 ` David Hildenbrand
2021-08-19 9:55 ` Joerg Roedel
2021-08-19 10:06 ` David Hildenbrand
2021-08-10 20:50 ` Dave Hansen
2021-08-12 21:08 ` Kirill A. Shutemov
2021-08-10 6:26 ` [PATCH 2/5] efi/x86: Implement " Kirill A. Shutemov
2021-08-10 17:50 ` Dave Hansen
2021-08-12 21:14 ` Kirill A. Shutemov
2021-08-12 21:43 ` Dave Hansen [this message]
2021-08-10 18:30 ` Dave Hansen
2021-08-10 19:08 ` Kirill A. Shutemov
2021-08-10 19:19 ` Dave Hansen
2021-08-12 21:17 ` Kirill A. Shutemov
2021-08-10 6:26 ` [PATCH 3/5] x86/boot/compressed: Handle " Kirill A. Shutemov
2021-08-10 6:26 ` [PATCH 4/5] x86/mm: Provide helpers for " Kirill A. Shutemov
2021-08-10 18:16 ` Dave Hansen
2021-08-12 20:31 ` Kirill A. Shutemov
2021-08-10 6:26 ` [PATCH 5/5] x86/tdx: Unaccepted memory support Kirill A. Shutemov
2021-08-10 14:08 ` [PATCH 0/5] x86: Impplement support for unaccepted memory Dave Hansen
2021-08-10 15:15 ` Kirill A. Shutemov
2021-08-10 15:51 ` Dave Hansen
2021-08-10 17:31 ` Kirill A. Shutemov
2021-08-10 17:36 ` Dave Hansen
2021-08-10 17:51 ` Kirill A. Shutemov
2021-08-10 18:19 ` Dave Hansen
2021-08-10 18:39 ` Kirill A. Shutemov
2021-08-12 8:23 ` Joerg Roedel
2021-08-12 10:10 ` Kirill A. Shutemov
2021-08-12 19:33 ` Andi Kleen
2021-08-12 20:22 ` Kirill A. Shutemov
2021-08-13 14:56 ` Joerg Roedel
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