From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Borislav Petkov <bp@alien8.de>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
Sean Christopherson <seanjc@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Joerg Roedel <jroedel@suse.de>, Ard Biesheuvel <ardb@kernel.org>,
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>,
Dave Hansen <dave.hansen@intel.com>,
Brijesh Singh <brijesh.singh@amd.com>,
Mike Rapoport <rppt@kernel.org>,
David Hildenbrand <david@redhat.com>,
x86@kernel.org, linux-mm@kvack.org, linux-coco@lists.linux.dev,
linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCHv5 08/12] x86/mm: Provide helpers for unaccepted memory
Date: Fri, 6 May 2022 19:13:59 +0300 [thread overview]
Message-ID: <20220506161359.4j5j5fxrw53fdbyr@box.shutemov.name> (raw)
In-Reply-To: <YnJfhiiHn+48H2vb@zn.tnic>
On Wed, May 04, 2022 at 01:12:06PM +0200, Borislav Petkov wrote:
> On Mon, Apr 25, 2022 at 06:39:30AM +0300, Kirill A. Shutemov wrote:
> > + unaccepted_memory = __va(boot_params.unaccepted_memory);
> > + range_start = start / PMD_SIZE;
> > +
> > + spin_lock_irqsave(&unaccepted_memory_lock, flags);
> > + for_each_set_bitrange_from(range_start, range_end, unaccepted_memory,
> > + DIV_ROUND_UP(end, PMD_SIZE)) {
> > + unsigned long len = range_end - range_start;
> > +
> > + /* Platform-specific memory-acceptance call goes here */
> > + panic("Cannot accept memory");
>
> Yeah, no, WARN_ON_ONCE() pls.
Failure to accept the memory is fatal. Why pretend it is not?
For TDX it will result in a crash on the first access. Prolonging the
suffering just make it harder to understand what happened.
> > + unsigned long flags;
> > + bool ret = false;
> > +
> > + spin_lock_irqsave(&unaccepted_memory_lock, flags);
> > + while (start < end) {
> > + if (test_bit(start / PMD_SIZE, unaccepted_memory)) {
> > + ret = true;
>
> Wait, what?
>
> That thing is lying: it'll return true for *some* PMD which is accepted
> but not the whole range of [start, end].
That's true. Note also that the check is inherently racy. Other CPU can
get the range or subrange accepted just after spin_unlock().
The check indicates that accept_memory() has to be called on the range
before first access.
Do you have problem with a name? Maybe has_unaccepted_memory()?
--
Kirill A. Shutemov
next prev parent reply other threads:[~2022-05-06 16:13 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-25 3:39 [PATCHv5 00/12] mm, x86/cc: Implement support for unaccepted memory Kirill A. Shutemov
2022-04-25 3:39 ` [PATCHv5 01/12] x86/boot/: Centralize __pa()/__va() definitions Kirill A. Shutemov
2022-04-25 7:37 ` David Hildenbrand
2022-04-25 7:52 ` Mike Rapoport
2022-04-25 3:39 ` [PATCHv5 02/12] mm: Add support for unaccepted memory Kirill A. Shutemov
2022-04-28 10:05 ` Borislav Petkov
2022-05-03 20:21 ` David Hildenbrand
2022-05-06 0:54 ` Kirill A. Shutemov
2022-04-25 3:39 ` [PATCHv5 03/12] efi/x86: Get full memory map in allocate_e820() Kirill A. Shutemov
2022-04-27 20:25 ` Borislav Petkov
2022-04-27 23:48 ` Kirill A. Shutemov
2022-04-28 10:02 ` Borislav Petkov
2022-04-25 3:39 ` [PATCHv5 04/12] x86/boot: Add infrastructure required for unaccepted memory support Kirill A. Shutemov
2022-04-29 10:58 ` Wander Lairson Costa
2022-05-02 13:38 ` Kirill A. Shutemov
2022-04-25 3:39 ` [PATCHv5 05/12] efi/x86: Implement support for unaccepted memory Kirill A. Shutemov
2022-04-29 10:53 ` Borislav Petkov
2022-05-02 13:40 ` Kirill A. Shutemov
2022-04-25 3:39 ` [PATCHv5 06/12] x86/boot/compressed: Handle " Kirill A. Shutemov
2022-04-27 0:17 ` Michael Roth
2022-04-27 14:19 ` Kirill A. Shutemov
2022-05-03 14:15 ` Borislav Petkov
2022-04-29 13:10 ` Wander Lairson Costa
2022-05-03 14:12 ` Borislav Petkov
2022-05-06 15:30 ` Kirill A. Shutemov
2022-05-10 11:03 ` Borislav Petkov
2022-05-13 5:34 ` Dionna Amalie Glaze
2022-05-13 9:01 ` Borislav Petkov
2022-05-13 14:45 ` Kirill A. Shutemov
2022-05-16 6:46 ` Xu, Min M
2022-05-31 22:40 ` Dionna Amalie Glaze
2022-06-01 15:49 ` Gupta, Pankaj
2022-06-01 16:20 ` Dionna Amalie Glaze
2022-06-01 19:34 ` Randy Dunlap
2022-06-01 21:19 ` Gupta, Pankaj
2022-06-02 12:51 ` Gupta, Pankaj
2022-06-02 15:31 ` Dionna Amalie Glaze
2022-06-07 17:28 ` Dionna Amalie Glaze
2022-06-07 18:15 ` Gupta, Pankaj
2022-04-25 3:39 ` [PATCHv5 07/12] x86/mm: Reserve unaccepted memory bitmap Kirill A. Shutemov
2022-04-29 13:19 ` Wander Lairson Costa
2022-05-04 11:04 ` Borislav Petkov
2022-04-25 3:39 ` [PATCHv5 08/12] x86/mm: Provide helpers for unaccepted memory Kirill A. Shutemov
2022-05-04 11:12 ` Borislav Petkov
2022-05-06 16:13 ` Kirill A. Shutemov [this message]
2022-05-10 18:32 ` Borislav Petkov
2022-05-11 1:15 ` Kirill A. Shutemov
2022-05-11 9:07 ` Borislav Petkov
2022-04-25 3:39 ` [PATCHv5 09/12] x86/tdx: Make _tdx_hypercall() and __tdx_module_call() available in boot stub Kirill A. Shutemov
2022-04-25 3:39 ` [PATCHv5 10/12] x86/tdx: Unaccepted memory support Kirill A. Shutemov
2022-05-05 10:12 ` Borislav Petkov
2022-05-06 20:44 ` Kirill A. Shutemov
2022-05-11 1:19 ` Kirill A. Shutemov
2022-05-11 9:13 ` Borislav Petkov
2022-04-25 3:39 ` [PATCHv5 11/12] mm/vmstat: Add counter for memory accepting Kirill A. Shutemov
2022-04-25 3:39 ` [PATCHv5 12/12] x86/mm: Report unaccepted memory in /proc/meminfo Kirill A. Shutemov
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