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Wed, 21 May 2025 19:39:35 +0000 (UTC) Date: Wed, 21 May 2025 21:39:34 +0200 From: Borislav Petkov To: Rik van Riel Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org, kernel-team@meta.com, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, nadav.amit@gmail.com, Rik van Riel , Yu-cheng Yu Subject: Re: [RFC v2 4/9] x86/mm: Introduce X86_FEATURE_RAR Message-ID: <20250521193934.GFaC4r9h38nCeHbt26@fat_crate.local> References: <20250520010350.1740223-1-riel@surriel.com> <20250520010350.1740223-5-riel@surriel.com> <20250521115343.GCaC2-x8LsmMApUkjQ@fat_crate.local> <20250521145339.GCaC3o87kpaouLZ_3D@fat_crate.local> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Queue-Id: 6B0F320003 X-Rspamd-Server: rspam09 X-Stat-Signature: jti6ygjg8s49e4tm6zctne46bht8zj7s X-HE-Tag: 1747856396-820131 X-HE-Meta: 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 yxQkc7b1 49k3YWRf2fZ1q/x3mf2+ncDCW/X6py7gvnsylgNhjsn5oXP0fshZVMu2IQWE2FqY/cd8b3gzTDpYlW9TYa5kJO3tyO8rBq+eMAhJNLf+lpWTvtjZGquk4H2cYxMk8brg/6e0iYQXQTqUxSBbVQSbMtTXnOoGRjFufe1mqegakclOLCLyh1YdWORNpZsrKiA9YkZibT2QUB74tpMTatbDtmQkNeXkEtCAr04C7m/pCLeDDp5j2ZTrJQjUU272gRd8Nh/PkeeBO5rrloD5uqtsvtPD5gAJ5+D0GZY1bgalTcyKThTXU4k6IKYCPdxyeySEFK36Eh6J+ggeVLAayCxJJHjf3YvozWCMuZjyFNOQv9PeQqG/KqZI/d7WmdcIwb9XmByGe0CimtyBRJJE= 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: List-Subscribe: List-Unsubscribe: On Wed, May 21, 2025 at 12:06:59PM -0400, Rik van Riel wrote: > On Wed, 2025-05-21 at 16:53 +0200, Borislav Petkov wrote: > > On Wed, May 21, 2025 at 09:57:52AM -0400, Rik van Riel wrote: > > > I had the same thought, and tried that already. > > > > > > It didn't work. > > > > Care to share why? > > > It resulted in RAR not being properly initialized, > and the system hanging when trying to use RAR to > flush the TLB. > > I don't remember exactly what sequence of events > was happening here, maybe something with the > boot CPU per-cpu RAR initialization being called > (or not, due to X86_FEATURE_RAR not being set) > before the systemwide initialization? I'm asking you to move it from this path to if (this_cpu->c_early_init) this_cpu->c_early_init(c); or if (this_cpu->c_bsp_init) this_cpu->c_bsp_init(c); a couple of lines above. This doesn't change anything: you're still running it on the BSP once. So I don't see how any of the above confusion would happen. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette