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Peter Anvin" , Paolo Bonzini , Wanpeng Li , Vitaly Kuznetsov , Andy Lutomirski , Frederic Weisbecker , "Paul E. McKenney" , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Andrew Morton , Uladzislau Rezki , Christoph Hellwig , Lorenzo Stoakes , Josh Poimboeuf , Jason Baron , Kees Cook , Sami Tolvanen , Ard Biesheuvel , Nicholas Piggin , Juerg Haefliger , Nicolas Saenz Julienne , "Kirill A. Shutemov" , Nadav Amit , Dan Carpenter , Chuang Wang , Yang Jihong , Petr Mladek , "Jason A. Donenfeld" , Song Liu , Julian Pidancet , Tom Lendacky , Dionna Glaze , Thomas =?iso-8859-1?Q?Wei=DFschuh?= , Juri Lelli , Marcelo Tosatti , Yair Podemsky , Daniel Wagner , Petr Tesarik Subject: Re: [RFC PATCH v3 13/15] context_tracking,x86: Add infrastructure to defer kernel TLBI Message-ID: <20241120153221.GM38972@noisy.programming.kicks-ass.net> References: <20241119153502.41361-1-vschneid@redhat.com> <20241119153502.41361-14-vschneid@redhat.com> <20241120152216.GM19989@noisy.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241120152216.GM19989@noisy.programming.kicks-ass.net> X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 259B240005 X-Stat-Signature: bx73rk4g7x9dryk3ii49rejdifgetjyq X-HE-Tag: 1732116706-961434 X-HE-Meta: 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 P7Y3jtxL 0cZ2IM/QnuA3vudwDBuiupi4GkbNYbsOoZ+dyZIrpcj3SpOthF3Lg/l1v3dcl+sbJFxXQUCTyixAnyuE5mGZlGeCwaOa1HxHXl8ykVhsdTGSV6rBoS7NUBVgQUBvsHymo4VlHQ/WvfaxLucK4z6LrBZi6kJi+TNsgjo771BpCXzN2SE2gFW3SjmkXxQIg/X4W8h/qPmccUbQrh1f5EC1/jZ6ZRKp6ZehavbGY/bGx+TOhamUCGdQxNmvKZlsG+T5YPH3m04upf9+PlvCkXiWWUNzMyjmPglmfLu5RRFOw2kkZPhZKGjCNZKyiPA== 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, Nov 20, 2024 at 04:22:16PM +0100, Peter Zijlstra wrote: > On Tue, Nov 19, 2024 at 04:35:00PM +0100, Valentin Schneider wrote: > > > +void noinstr __flush_tlb_all_noinstr(void) > > +{ > > + /* > > + * This is for invocation in early entry code that cannot be > > + * instrumented. A RMW to CR4 works for most cases, but relies on > > + * being able to flip either of the PGE or PCIDE bits. Flipping CR4.PCID > > + * would require also resetting CR3.PCID, so just try with CR4.PGE, else > > + * do the CR3 write. > > + * > > + * XXX: this gives paravirt the finger. > > + */ > > + if (cpu_feature_enabled(X86_FEATURE_PGE)) > > + __native_tlb_flush_global_noinstr(this_cpu_read(cpu_tlbstate.cr4)); > > + else > > + native_flush_tlb_local_noinstr(); > > +} > > Urgh, so that's a lot of ugleh, and cr4 has that pinning stuff and gah. > > Why not always just do the CR3 write and call it a day? That should also > work for paravirt, no? Just make the whole write_cr3 thing noinstr and > voila. Oh gawd, just having looked at xen_write_cr3() this might not be entirely trivial to mark noinstr :/