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Shutemov" To: Ard Biesheuvel Cc: Matthew Wilcox , Borislav Petkov , Andy Lutomirski , Dave Hansen , Sean Christopherson , Andrew Morton , Joerg Roedel , Andi Kleen , Kuppuswamy Sathyanarayanan , David Rientjes , Vlastimil Babka , Tom Lendacky , Thomas Gleixner , Peter Zijlstra , Paolo Bonzini , Ingo Molnar , Dario Faggioli , Mike Rapoport , David Hildenbrand , Mel Gorman , marcelo.cerri@canonical.com, tim.gardner@canonical.com, philip.cox@canonical.com, aarcange@redhat.com, peterx@redhat.com, x86@kernel.org, linux-mm@kvack.org, linux-coco@lists.linux.dev, linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org, stable@kernel.org, Nikolay Borisov Subject: Re: [PATCHv2] efi/unaccepted: Fix soft lockups caused by parallel memory acceptance Message-ID: <20231017094403.g6laxp2c3vwzt2sw@box.shutemov.name> References: <20231016163122.12855-1-kirill.shutemov@linux.intel.com> <20231016213932.6cscnn6tsnzsnvmf@box.shutemov.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 23D47C0012 X-Stat-Signature: 1e5u38daw13z1iu67x4hmiwwji4q3p98 X-HE-Tag: 1697535868-74439 X-HE-Meta: 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 l5LaMRCB uTI7oLUKUTWje7BeV8TYRxlpEJ9WCMeUeQXevtbjNKEofcQr31n3XNHC+mQWySQjwK0x35pRBAg2F0Ltige40/NwAaESFyVYioc4hlWtqz+QCG3BgOHEdpqP6ZUZEsnougg3LrBRsl/FH0c8= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Oct 17, 2023 at 09:42:13AM +0200, Ard Biesheuvel wrote: > On Mon, 16 Oct 2023 at 23:39, Kirill A. Shutemov > wrote: > > > > On Mon, Oct 16, 2023 at 06:55:41PM +0100, Matthew Wilcox wrote: > > > On Mon, Oct 16, 2023 at 07:31:22PM +0300, Kirill A. Shutemov wrote: > > > > v2: > > > > - Fix deadlock (Vlastimil); > > > > - Fix comments (Vlastimil); > > > > - s/cond_resched()/cpu_relax()/ -- cond_resched() cannot be called > > > > from atomic context; > > > > > > Isn't there an implicit cpu_relax() while we're spinning? Does this > > > really accomplish anything? > > > > You are right. It is useless. I will drop it in v3. > > > > I can drop that bit when applying the patch. > > One question I have is whether the sequence > > spin_lock_irqsave(&unaccepted_memory_lock, flags); > ... > spin_unlock(&unaccepted_memory_lock); > arch_accept_memory(phys_start, phys_end); > spin_lock(&unaccepted_memory_lock); > ... > spin_unlock_irqrestore(&unaccepted_memory_lock, flags); > > is considered sound and is supported by all architectures? I am not an locking expert and only tested it on x86. But what potential issue do you see? -- Kiryl Shutsemau / Kirill A. Shutemov