From: Thomas Gleixner <tglx@linutronix.de> To: Dave Hansen <dave.hansen@linux.intel.com> Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, moritz.lipp@iaik.tugraz.at, daniel.gruss@iaik.tugraz.at, michael.schwarz@iaik.tugraz.at, luto@kernel.org, torvalds@linux-foundation.org, keescook@google.com, hughd@google.com, x86@kernel.org Subject: Re: [PATCH 04/23] x86, tlb: make CR4-based TLB flushes more robust Date: Wed, 1 Nov 2017 22:25:26 +0100 (CET) [thread overview] Message-ID: <alpine.DEB.2.20.1711012222330.1942@nanos> (raw) In-Reply-To: <20171031223154.67F15B2A@viggo.jf.intel.com> On Tue, 31 Oct 2017, Dave Hansen wrote: > Our CR4-based TLB flush currently requries global pages to be > supported *and* enabled. But, we really only need for them to be > supported. Make the code more robust by alllowing X86_CR4_PGE to > clear as well as set. That's not what the patch is actually doing. > cr4 = this_cpu_read(cpu_tlbstate.cr4); > - /* clear PGE */ > - native_write_cr4(cr4 & ~X86_CR4_PGE); > - /* write old PGE again and flush TLBs */ > + /* > + * This function is only called on systems that support X86_CR4_PGE > + * and where always set X86_CR4_PGE. Warn if we are called without > + * PGE set. > + */ > + WARN_ON_ONCE(!(cr4 & X86_CR4_PGE)); Because if CR4_PGE is not set, this warning triggers. So this defeats the toggle mode you are implementing. > + /* > + * Architecturally, any _change_ to X86_CR4_PGE will fully flush the > + * TLB of all entries including all entries in all PCIDs and all > + * global pages. Make sure that we _change_ the bit, regardless of > + * whether we had X86_CR4_PGE set in the first place. > + */ > + native_write_cr4(cr4 ^ X86_CR4_PGE); > + /* Put original CR3 value back: */ That want's to be CR4. Restoring CR3 to CR4 might be suboptimal. > native_write_cr4(cr4); Thanks, tglx
WARNING: multiple messages have this Message-ID (diff)
From: Thomas Gleixner <tglx@linutronix.de> To: Dave Hansen <dave.hansen@linux.intel.com> Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, moritz.lipp@iaik.tugraz.at, daniel.gruss@iaik.tugraz.at, michael.schwarz@iaik.tugraz.at, luto@kernel.org, torvalds@linux-foundation.org, keescook@google.com, hughd@google.com, x86@kernel.org Subject: Re: [PATCH 04/23] x86, tlb: make CR4-based TLB flushes more robust Date: Wed, 1 Nov 2017 22:25:26 +0100 (CET) [thread overview] Message-ID: <alpine.DEB.2.20.1711012222330.1942@nanos> (raw) In-Reply-To: <20171031223154.67F15B2A@viggo.jf.intel.com> On Tue, 31 Oct 2017, Dave Hansen wrote: > Our CR4-based TLB flush currently requries global pages to be > supported *and* enabled. But, we really only need for them to be > supported. Make the code more robust by alllowing X86_CR4_PGE to > clear as well as set. That's not what the patch is actually doing. > cr4 = this_cpu_read(cpu_tlbstate.cr4); > - /* clear PGE */ > - native_write_cr4(cr4 & ~X86_CR4_PGE); > - /* write old PGE again and flush TLBs */ > + /* > + * This function is only called on systems that support X86_CR4_PGE > + * and where always set X86_CR4_PGE. Warn if we are called without > + * PGE set. > + */ > + WARN_ON_ONCE(!(cr4 & X86_CR4_PGE)); Because if CR4_PGE is not set, this warning triggers. So this defeats the toggle mode you are implementing. > + /* > + * Architecturally, any _change_ to X86_CR4_PGE will fully flush the > + * TLB of all entries including all entries in all PCIDs and all > + * global pages. Make sure that we _change_ the bit, regardless of > + * whether we had X86_CR4_PGE set in the first place. > + */ > + native_write_cr4(cr4 ^ X86_CR4_PGE); > + /* Put original CR3 value back: */ That want's to be CR4. Restoring CR3 to CR4 might be suboptimal. > native_write_cr4(cr4); Thanks, tglx -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2017-11-01 21:25 UTC|newest] Thread overview: 204+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-10-31 22:31 [PATCH 00/23] KAISER: unmap most of the kernel from userspace page tables Dave Hansen 2017-10-31 22:31 ` Dave Hansen 2017-10-31 22:31 ` [PATCH 01/23] x86, kaiser: prepare assembly for entry/exit CR3 switching Dave Hansen 2017-10-31 22:31 ` Dave Hansen 2017-11-01 0:43 ` Brian Gerst 2017-11-01 0:43 ` Brian Gerst 2017-11-01 1:08 ` Dave Hansen 2017-11-01 1:08 ` Dave Hansen 2017-11-01 18:18 ` Borislav Petkov 2017-11-01 18:18 ` Borislav Petkov 2017-11-01 18:27 ` Dave Hansen 2017-11-01 18:27 ` Dave Hansen 2017-11-01 20:42 ` Borislav Petkov 2017-11-01 20:42 ` Borislav Petkov 2017-11-01 21:01 ` Thomas Gleixner 2017-11-01 21:01 ` Thomas Gleixner 2017-11-01 22:58 ` Dave Hansen 2017-11-01 22:58 ` Dave Hansen 2017-10-31 22:31 ` [PATCH 02/23] x86, kaiser: do not set _PAGE_USER for init_mm page tables Dave Hansen 2017-10-31 22:31 ` Dave Hansen 2017-11-01 21:11 ` Thomas Gleixner 2017-11-01 21:11 ` Thomas Gleixner 2017-11-01 21:24 ` Andy Lutomirski 2017-11-01 21:24 ` Andy Lutomirski 2017-11-01 21:28 ` Thomas Gleixner 2017-11-01 21:28 ` Thomas Gleixner 2017-11-01 21:52 ` Dave Hansen 2017-11-01 21:52 ` Dave Hansen 2017-11-01 22:11 ` Thomas Gleixner 2017-11-01 22:11 ` Thomas Gleixner 2017-11-01 22:12 ` Linus Torvalds 2017-11-01 22:12 ` Linus Torvalds 2017-11-01 22:20 ` Thomas Gleixner 2017-11-01 22:20 ` Thomas Gleixner 2017-11-01 22:45 ` Kees Cook 2017-11-01 22:45 ` Kees Cook 2017-11-02 7:10 ` Andy Lutomirski 2017-11-02 7:10 ` Andy Lutomirski 2017-11-02 11:33 ` Thomas Gleixner 2017-11-02 11:33 ` Thomas Gleixner 2017-11-02 11:59 ` Andy Lutomirski 2017-11-02 11:59 ` Andy Lutomirski 2017-11-02 12:56 ` Thomas Gleixner 2017-11-02 12:56 ` Thomas Gleixner 2017-11-02 16:38 ` Dave Hansen 2017-11-02 16:38 ` Dave Hansen 2017-11-02 18:19 ` Andy Lutomirski 2017-11-02 18:19 ` Andy Lutomirski 2017-11-02 18:24 ` Thomas Gleixner 2017-11-02 18:24 ` Thomas Gleixner 2017-11-02 18:24 ` Linus Torvalds 2017-11-02 18:24 ` Linus Torvalds 2017-11-02 18:40 ` Thomas Gleixner 2017-11-02 18:40 ` Thomas Gleixner 2017-11-02 18:57 ` Linus Torvalds 2017-11-02 18:57 ` Linus Torvalds 2017-11-02 21:41 ` Thomas Gleixner 2017-11-02 21:41 ` Thomas Gleixner 2017-11-02 7:07 ` Andy Lutomirski 2017-11-02 7:07 ` Andy Lutomirski 2017-11-02 11:21 ` Thomas Gleixner 2017-11-02 11:21 ` Thomas Gleixner 2017-10-31 22:31 ` [PATCH 03/23] x86, kaiser: disable global pages Dave Hansen 2017-10-31 22:31 ` Dave Hansen 2017-11-01 21:18 ` Thomas Gleixner 2017-11-01 21:18 ` Thomas Gleixner 2017-11-01 22:12 ` Dave Hansen 2017-11-01 22:12 ` Dave Hansen 2017-11-01 22:28 ` Thomas Gleixner 2017-11-01 22:28 ` Thomas Gleixner 2017-10-31 22:31 ` [PATCH 04/23] x86, tlb: make CR4-based TLB flushes more robust Dave Hansen 2017-10-31 22:31 ` Dave Hansen 2017-11-01 8:01 ` Andy Lutomirski 2017-11-01 8:01 ` Andy Lutomirski 2017-11-01 10:11 ` Kirill A. Shutemov 2017-11-01 10:11 ` Kirill A. Shutemov 2017-11-01 10:38 ` Andy Lutomirski 2017-11-01 10:38 ` Andy Lutomirski 2017-11-01 10:56 ` Kirill A. Shutemov 2017-11-01 10:56 ` Kirill A. Shutemov 2017-11-01 11:18 ` Andy Lutomirski 2017-11-01 11:18 ` Andy Lutomirski 2017-11-01 22:21 ` Dave Hansen 2017-11-01 22:21 ` Dave Hansen 2017-11-01 21:25 ` Thomas Gleixner [this message] 2017-11-01 21:25 ` Thomas Gleixner 2017-11-01 22:24 ` Dave Hansen 2017-11-01 22:24 ` Dave Hansen 2017-11-01 22:30 ` Thomas Gleixner 2017-11-01 22:30 ` Thomas Gleixner 2017-10-31 22:31 ` [PATCH 05/23] x86, mm: document X86_CR4_PGE toggling behavior Dave Hansen 2017-10-31 22:31 ` Dave Hansen 2017-10-31 23:31 ` Kees Cook 2017-10-31 23:31 ` Kees Cook 2017-10-31 22:31 ` [PATCH 06/23] x86, kaiser: introduce user-mapped percpu areas Dave Hansen 2017-10-31 22:31 ` Dave Hansen 2017-11-01 21:47 ` Thomas Gleixner 2017-11-01 21:47 ` Thomas Gleixner 2017-10-31 22:31 ` [PATCH 07/23] x86, kaiser: unmap kernel from userspace page tables (core patch) Dave Hansen 2017-10-31 22:31 ` Dave Hansen 2017-10-31 22:32 ` [PATCH 08/23] x86, kaiser: only populate shadow page tables for userspace Dave Hansen 2017-10-31 22:32 ` Dave Hansen 2017-10-31 23:35 ` Kees Cook 2017-10-31 23:35 ` Kees Cook 2017-10-31 22:32 ` [PATCH 09/23] x86, kaiser: allow NX to be set in p4d/pgd Dave Hansen 2017-10-31 22:32 ` Dave Hansen 2017-10-31 22:32 ` [PATCH 10/23] x86, kaiser: make sure static PGDs are 8k in size Dave Hansen 2017-10-31 22:32 ` Dave Hansen 2017-10-31 22:32 ` [PATCH 11/23] x86, kaiser: map GDT into user page tables Dave Hansen 2017-10-31 22:32 ` Dave Hansen 2017-10-31 22:32 ` [PATCH 12/23] x86, kaiser: map dynamically-allocated LDTs Dave Hansen 2017-10-31 22:32 ` Dave Hansen 2017-11-01 8:00 ` Andy Lutomirski 2017-11-01 8:00 ` Andy Lutomirski 2017-11-01 8:06 ` Ingo Molnar 2017-11-01 8:06 ` Ingo Molnar 2017-10-31 22:32 ` [PATCH 13/23] x86, kaiser: map espfix structures Dave Hansen 2017-10-31 22:32 ` Dave Hansen 2017-10-31 22:32 ` [PATCH 14/23] x86, kaiser: map entry stack variables Dave Hansen 2017-10-31 22:32 ` Dave Hansen 2017-10-31 22:32 ` [PATCH 15/23] x86, kaiser: map trace interrupt entry Dave Hansen 2017-10-31 22:32 ` Dave Hansen 2017-10-31 22:32 ` [PATCH 16/23] x86, kaiser: map debug IDT tables Dave Hansen 2017-10-31 22:32 ` Dave Hansen 2017-10-31 22:32 ` [PATCH 17/23] x86, kaiser: map virtually-addressed performance monitoring buffers Dave Hansen 2017-10-31 22:32 ` Dave Hansen 2017-10-31 22:32 ` [PATCH 18/23] x86, mm: Move CR3 construction functions Dave Hansen 2017-10-31 22:32 ` Dave Hansen 2017-10-31 22:32 ` [PATCH 19/23] x86, mm: remove hard-coded ASID limit checks Dave Hansen 2017-10-31 22:32 ` Dave Hansen 2017-10-31 22:32 ` [PATCH 20/23] x86, mm: put mmu-to-h/w ASID translation in one place Dave Hansen 2017-10-31 22:32 ` Dave Hansen 2017-10-31 22:32 ` [PATCH 21/23] x86, pcid, kaiser: allow flushing for future ASID switches Dave Hansen 2017-10-31 22:32 ` Dave Hansen 2017-11-01 8:03 ` Andy Lutomirski 2017-11-01 8:03 ` Andy Lutomirski 2017-11-01 14:17 ` Dave Hansen 2017-11-01 14:17 ` Dave Hansen 2017-11-01 20:31 ` Andy Lutomirski 2017-11-01 20:31 ` Andy Lutomirski 2017-11-01 20:59 ` Dave Hansen 2017-11-01 20:59 ` Dave Hansen 2017-11-01 21:04 ` Andy Lutomirski 2017-11-01 21:04 ` Andy Lutomirski 2017-11-01 21:06 ` Dave Hansen 2017-11-01 21:06 ` Dave Hansen 2017-10-31 22:32 ` [PATCH 22/23] x86, kaiser: use PCID feature to make user and kernel switches faster Dave Hansen 2017-10-31 22:32 ` Dave Hansen 2017-10-31 22:32 ` [PATCH 23/23] x86, kaiser: add Kconfig Dave Hansen 2017-10-31 22:32 ` Dave Hansen 2017-10-31 23:59 ` Kees Cook 2017-10-31 23:59 ` Kees Cook 2017-11-01 9:07 ` Borislav Petkov 2017-11-01 9:07 ` Borislav Petkov 2017-10-31 23:27 ` [PATCH 00/23] KAISER: unmap most of the kernel from userspace page tables Linus Torvalds 2017-10-31 23:27 ` Linus Torvalds 2017-10-31 23:44 ` Dave Hansen 2017-10-31 23:44 ` Dave Hansen 2017-11-01 0:21 ` Dave Hansen 2017-11-01 0:21 ` Dave Hansen 2017-11-01 7:59 ` Andy Lutomirski 2017-11-01 7:59 ` Andy Lutomirski 2017-11-01 16:08 ` Linus Torvalds 2017-11-01 16:08 ` Linus Torvalds 2017-11-01 17:31 ` Dave Hansen 2017-11-01 17:58 ` Randy Dunlap 2017-11-01 17:58 ` Randy Dunlap 2017-11-01 18:27 ` Linus Torvalds 2017-11-01 18:27 ` Linus Torvalds 2017-11-01 18:46 ` Dave Hansen 2017-11-01 18:46 ` Dave Hansen 2017-11-01 19:05 ` Linus Torvalds 2017-11-01 19:05 ` Linus Torvalds 2017-11-01 20:33 ` Andy Lutomirski 2017-11-01 20:33 ` Andy Lutomirski 2017-11-02 7:32 ` Andy Lutomirski 2017-11-02 7:32 ` Andy Lutomirski 2017-11-02 7:54 ` Andy Lutomirski 2017-11-02 7:54 ` Andy Lutomirski 2017-11-01 15:53 ` Dave Hansen 2017-11-01 15:53 ` Dave Hansen 2017-11-01 8:54 ` Ingo Molnar 2017-11-01 8:54 ` Ingo Molnar 2017-11-01 14:09 ` Thomas Gleixner 2017-11-01 14:09 ` Thomas Gleixner 2017-11-01 22:14 ` Dave Hansen 2017-11-01 22:14 ` Dave Hansen 2017-11-01 22:28 ` Linus Torvalds 2017-11-01 22:28 ` Linus Torvalds 2017-11-02 8:03 ` Peter Zijlstra 2017-11-02 8:03 ` Peter Zijlstra 2017-11-03 11:07 ` Kirill A. Shutemov 2017-11-03 11:07 ` Kirill A. Shutemov 2017-11-02 19:01 ` Will Deacon 2017-11-02 19:01 ` Will Deacon 2017-11-02 19:01 ` Will Deacon 2017-11-02 19:38 ` Dave Hansen 2017-11-02 19:38 ` Dave Hansen 2017-11-02 19:38 ` Dave Hansen 2017-11-03 13:41 ` Will Deacon 2017-11-03 13:41 ` Will Deacon 2017-11-03 13:41 ` Will Deacon 2017-11-22 16:19 ` Pavel Machek 2017-11-23 10:47 ` Pavel Machek
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