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Shutemov" To: Peter Zijlstra Cc: Bharata B Rao , ananth.narayan@amd.com, "Kirill A. Shutemov" , Dave Hansen , Andy Lutomirski , x86@kernel.org, Kostya Serebryany , Andrey Ryabinin , Andrey Konovalov , Alexander Potapenko , Taras Madan , Dmitry Vyukov , "H . J . Lu" , Andi Kleen , Rick Edgecombe , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCHv8 00/11] Linear Address Masking enabling Message-ID: <20220905164708.ewx5lulbqdjrk3mx@box.shutemov.name> References: <20220830010104.1282-1-kirill.shutemov@linux.intel.com> <20220904010001.knlcejmw4lg2uzy3@box.shutemov.name> <64519d0b-b696-db47-52c2-303451e10c09@amd.com> <20220905134457.a2f7uluq42frsgwe@box.shutemov.name> <20220905153517.k6ctaqqtkcyu2zmn@box.shutemov.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1662396435; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=ppgpksPj3y7l/SkP6fbnYixZ5NsMp5i64ReQbaQaQMA=; b=lzMPEH5LMkPFKQ9GPTBGkDzq7NlhILthoQngsl+bEhMKFtk/7KqWS9EaWOg4+SaMFxTGCE LVhOzs8oXItpoyfEsFoaC+Pza+1OU5+XCIF89uJpItZg31IyEgEy/VyVq6QLciQhvWTi3W YBS4jxmbQACpVJ0e1t25cfX1FKkMOd0= ARC-Authentication-Results: i=1; imf17.hostedemail.com; dkim=pass header.d=shutemov.name header.s=fm3 header.b=yyKUbp7m; dkim=pass header.d=messagingengine.com header.s=fm1 header.b=PSxp21Ed; spf=pass (imf17.hostedemail.com: domain of kirill@shutemov.name designates 64.147.123.20 as permitted sender) smtp.mailfrom=kirill@shutemov.name; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1662396435; a=rsa-sha256; cv=none; b=gJt0KcrRQfcwzmNLWdoKf8g4CCaJ/s+7ih4IxXjlwbnbEK9E5FOV1zlVFlgV3Raw8ZcIY7 YCC+Mh9nZodkJ2OECb9NSreqKJzXQ5nSV/yXPMbyYpj152fWN8rMPufVsAGh1TbG//IAEF kzZ9X8sVIqsICtHzvZdvRHPHDHQic4c= X-Rspam-User: Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=shutemov.name header.s=fm3 header.b=yyKUbp7m; dkim=pass header.d=messagingengine.com header.s=fm1 header.b=PSxp21Ed; spf=pass (imf17.hostedemail.com: domain of kirill@shutemov.name designates 64.147.123.20 as permitted sender) smtp.mailfrom=kirill@shutemov.name; dmarc=none X-Rspamd-Server: rspam07 X-Stat-Signature: 5fxcn4i8gwgec7coh111dnhc7zdbkotd X-Rspamd-Queue-Id: 2272340065 X-HE-Tag: 1662396435-372086 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 Mon, Sep 05, 2022 at 05:46:49PM +0200, Peter Zijlstra wrote: > On Mon, Sep 05, 2022 at 06:35:17PM +0300, Kirill A. Shutemov wrote: > > What about something like this? > > > > diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h > > index 803241dfc473..868d2730884b 100644 > > --- a/arch/x86/include/asm/uaccess.h > > +++ b/arch/x86/include/asm/uaccess.h > > @@ -30,8 +30,10 @@ static inline bool pagefault_disabled(void); > > */ > > #define untagged_addr(mm, addr) ({ \ > > u64 __addr = (__force u64)(addr); \ > > - s64 sign = (s64)__addr >> 63; \ > > - __addr &= (mm)->context.untag_mask | sign; \ > > + if (static_cpu_has(X86_FEATURE_LAM)) { \ > > + s64 sign = (s64)__addr >> 63; \ > > + __addr &= (mm)->context.untag_mask | sign; \ > > + } \ > > (__force __typeof__(addr))__addr; \ > > }) > > Well, if you go throught the trouble of adding it, might as well use a > regular static branch and only enable it once there's an actual user, > no? Fair enough. How about this? diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h index 803241dfc473..1a03c65a9c0f 100644 --- a/arch/x86/include/asm/uaccess.h +++ b/arch/x86/include/asm/uaccess.h @@ -22,6 +22,8 @@ static inline bool pagefault_disabled(void); #endif #ifdef CONFIG_X86_64 +DECLARE_STATIC_KEY_FALSE(tagged_addr_key); + /* * Mask out tag bits from the address. * @@ -30,8 +32,10 @@ static inline bool pagefault_disabled(void); */ #define untagged_addr(mm, addr) ({ \ u64 __addr = (__force u64)(addr); \ - s64 sign = (s64)__addr >> 63; \ - __addr &= (mm)->context.untag_mask | sign; \ + if (static_branch_unlikely(&tagged_addr_key)) { \ + s64 sign = (s64)__addr >> 63; \ + __addr &= (mm)->context.untag_mask | sign; \ + } \ (__force __typeof__(addr))__addr; \ }) diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 337f80a0862f..63194bf43c9a 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -742,6 +742,9 @@ static long prctl_map_vdso(const struct vdso_image *image, unsigned long addr) } #endif +DEFINE_STATIC_KEY_FALSE(tagged_addr_key); +EXPORT_SYMBOL_GPL(tagged_addr_key); + static void enable_lam_func(void *mm) { struct mm_struct *loaded_mm = this_cpu_read(cpu_tlbstate.loaded_mm); @@ -813,6 +816,7 @@ static int prctl_enable_tagged_addr(struct mm_struct *mm, unsigned long nr_bits) } on_each_cpu_mask(mm_cpumask(mm), enable_lam_func, mm, true); + static_branch_enable(&tagged_addr_key); out: mutex_unlock(&mm->context.lock); mmap_write_unlock(mm); -- Kiryl Shutsemau / Kirill A. Shutemov