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Shutemov" Cc: 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: [PATCHv6 06/11] x86/mm: Provide arch_prctl() interface for LAM Message-ID: References: <20220815041803.17954-1-kirill.shutemov@linux.intel.com> <20220815041803.17954-7-kirill.shutemov@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220815041803.17954-7-kirill.shutemov@linux.intel.com> ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1660570643; 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=OhsclZAw4++SCZJt6PxhgQPcNRPDZfNSWoLpFgsjkGI=; b=G4bH8B6Qs/g74riwGh+Y1VVWzHUBwVCz5dm2UrVDhTbGGzWKwgv18my8zRqw51BOWf8uCQ 8dVYsVSJorCBPZDiMeEd6ZAM7XZD0ZjFnuWXnC99wUCl39tvftCPMYMchreRR8T4/jYJwD tzsg7jWV1j51xrtagr0RkHw5mjrNJ6Q= ARC-Authentication-Results: i=1; imf30.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=FWhBtbK8; dmarc=none; spf=none (imf30.hostedemail.com: domain of peterz@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=peterz@infradead.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1660570643; a=rsa-sha256; cv=none; b=Yw8mCXf8uvbXvLqWqczlyX/GkE18dUfPwMmQzcGD5zGsrKAiQAv+WOzg1010Yr4g1fLQc4 Cx2UF1TmkPCqCcLj7mgi+Pop4oSGuZtn24it3oFCH2Z5BE2hM8b1TAZns6NvpHZModsxcs 4NFJ4Z3XePQwPEJTpktyhbA84GZUPWc= Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=FWhBtbK8; dmarc=none; spf=none (imf30.hostedemail.com: domain of peterz@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=peterz@infradead.org X-Rspam-User: X-Stat-Signature: g8r38jsdaszh74kwz46z349kph5zx1m4 X-Rspamd-Queue-Id: A818C801AA X-Rspamd-Server: rspam11 X-HE-Tag: 1660570643-893538 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, Aug 15, 2022 at 07:17:58AM +0300, Kirill A. Shutemov wrote: > +static void enable_lam_func(void *mm) > +{ > + struct mm_struct *loaded_mm = this_cpu_read(cpu_tlbstate.loaded_mm); > + unsigned long lam_mask; > + unsigned long cr3; > + > + if (loaded_mm != mm) > + return; > + > + lam_mask = READ_ONCE(loaded_mm->context.lam_cr3_mask); > + > + /* Update CR3 to get LAM active on the CPU */ > + cr3 = __read_cr3(); > + cr3 &= ~(X86_CR3_LAM_U48 | X86_CR3_LAM_U57); > + cr3 |= lam_mask; > + write_cr3(cr3); > + set_tlbstate_cr3_lam_mask(lam_mask); > +} > + > +static int prctl_enable_tagged_addr(struct mm_struct *mm, unsigned long nr_bits) > +{ > + int ret = 0; > + > + if (!cpu_feature_enabled(X86_FEATURE_LAM)) > + return -ENODEV; > + > + mutex_lock(&mm->context.lock); > + > + /* Already enabled? */ > + if (mm->context.lam_cr3_mask) { > + ret = -EBUSY; > + goto out; > + } > + > + if (!nr_bits) { > + ret = -EINVAL; > + goto out; > + } else if (nr_bits <= 6) { > + mm->context.lam_cr3_mask = X86_CR3_LAM_U57; > + mm->context.untag_mask = ~GENMASK(62, 57); > + } else { > + ret = -EINVAL; > + goto out; > + } > + > + /* Make lam_cr3_mask and untag_mask visible on other CPUs */ > + smp_mb(); smp_mb() doesn't make visible -- it is about ordering, what does it order against that the below on_each_cpu_mask() doesn't already take care of? > + > + on_each_cpu_mask(mm_cpumask(mm), enable_lam_func, mm, true); > +out: > + mutex_unlock(&mm->context.lock); > + return ret; > +}