From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2AFCDC3A5A3 for ; Tue, 27 Aug 2019 05:53:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EB8E62173E for ; Tue, 27 Aug 2019 05:53:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728823AbfH0Fxz (ORCPT ); Tue, 27 Aug 2019 01:53:55 -0400 Received: from mx2.suse.de ([195.135.220.15]:50354 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725811AbfH0Fxy (ORCPT ); Tue, 27 Aug 2019 01:53:54 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id C0527ACC1; Tue, 27 Aug 2019 05:53:52 +0000 (UTC) Subject: Re: [RFC PATCH v2 1/3] x86/mm/tlb: Change __flush_tlb_one_user interface To: Nadav Amit Cc: Peter Zijlstra , Andy Lutomirski , StefanoStabellini , the arch/x86 maintainers , Thomas Gleixner , Dave Hansen , xen-devel , Boris Ostrovsky , Ingo Molnar , "linux-kernel@vger.kernel.org" References: <20190823225248.15597-1-namit@vmware.com> <20190823225248.15597-2-namit@vmware.com> <41C46D29-A0F3-48AA-BC28-2480F24D60FF@vmware.com> From: Juergen Gross Message-ID: Date: Tue, 27 Aug 2019 07:53:51 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <41C46D29-A0F3-48AA-BC28-2480F24D60FF@vmware.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: de-DE Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 26.08.19 18:38, Nadav Amit wrote: >> On Aug 26, 2019, at 12:51 AM, Juergen Gross wrote: >> >> On 24.08.19 00:52, Nadav Amit wrote: >>> __flush_tlb_one_user() currently flushes a single entry, and flushes it >>> both in the kernel and user page-tables, when PTI is enabled. >>> Change __flush_tlb_one_user() and related interfaces into >>> __flush_tlb_range() that flushes a range and does not flush the user >>> page-table. >>> This refactoring is needed for the next patch, but regardless makes >>> sense and has several advantages. First, only Xen-PV, which does not >>> use PTI, implements the paravirtual interface of flush_tlb_one_user() so >>> nothing is broken by separating the user and kernel page-table flushes, >>> and the interface is more intuitive. >>> Second, INVLPG can flush unrelated mappings, and it is also a >>> serializing instruction. It is better to have a tight loop that flushes >>> the entries. >>> Third, currently __flush_tlb_one_kernel() also flushes the user >>> page-tables, which is not needed. This allows to avoid this redundant >>> flush. >>> Cc: Boris Ostrovsky >>> Cc: Juergen Gross >>> Cc: Stefano Stabellini >>> Cc: xen-devel@lists.xenproject.org >>> Signed-off-by: Nadav Amit >>> --- >>> arch/x86/include/asm/paravirt.h | 5 ++-- >>> arch/x86/include/asm/paravirt_types.h | 3 ++- >>> arch/x86/include/asm/tlbflush.h | 24 +++++------------ >>> arch/x86/kernel/paravirt.c | 7 ++--- >>> arch/x86/mm/tlb.c | 39 ++++++++++++++++++++++----- >>> arch/x86/xen/mmu_pv.c | 21 +++++++++------ >>> 6 files changed, 62 insertions(+), 37 deletions(-) >> >> ... >> >>> diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c >>> index 48f7c7eb4dbc..ed68657f5e77 100644 >>> --- a/arch/x86/xen/mmu_pv.c >>> +++ b/arch/x86/xen/mmu_pv.c >>> @@ -1325,22 +1325,27 @@ static noinline void xen_flush_tlb(void) >>> preempt_enable(); >>> } >>> -static void xen_flush_tlb_one_user(unsigned long addr) >>> +static void xen_flush_tlb_range(unsigned long start, unsigned long end, >>> + u8 stride_shift) >>> { >>> struct mmuext_op *op; >>> struct multicall_space mcs; >>> - >>> - trace_xen_mmu_flush_tlb_one_user(addr); >>> + unsigned long addr; >>> preempt_disable(); >>> mcs = xen_mc_entry(sizeof(*op)); >>> op = mcs.args; >>> - op->cmd = MMUEXT_INVLPG_LOCAL; >>> - op->arg1.linear_addr = addr & PAGE_MASK; >>> - MULTI_mmuext_op(mcs.mc, op, 1, NULL, DOMID_SELF); >>> - xen_mc_issue(PARAVIRT_LAZY_MMU); >>> + for (addr = start; addr < end; addr += 1ul << stride_shift) { >>> + trace_xen_mmu_flush_tlb_one_user(addr); >>> + >>> + op->cmd = MMUEXT_INVLPG_LOCAL; >>> + op->arg1.linear_addr = addr & PAGE_MASK; >>> + MULTI_mmuext_op(mcs.mc, op, 1, NULL, DOMID_SELF); >>> + >>> + xen_mc_issue(PARAVIRT_LAZY_MMU); >>> + } >> >> For this kind of usage (a loop) you should: >> >> - replace the call of xen_mc_entry() with xen_mc_batch() >> - use xen_extend_mmuext_op() for each loop iteration >> - call xen_mc_issue() after the loop >> >> Additionally I'd like you to replace trace_xen_mmu_flush_tlb_one_user() >> with trace_xen_mmu_flush_tlb_range() taking all three parameters and >> keep it where it was (out of the loop). >> >> The paravirt parts seem to be okay. > > Thanks for the quick response. I don’t think the preempt_disable/enable() is > needed in this case, but I kept them. Does the following match what you had > in mind? Yes, it does. BTW, preempt_disable/enable() is needed as xen_mc_batch() ... xen_mc_issue() is using a percpu buffer. Juergen > > --- > arch/x86/xen/mmu_pv.c | 25 ++++++++++++++----------- > include/trace/events/xen.h | 18 ++++++++++++------ > 2 files changed, 26 insertions(+), 17 deletions(-) > > diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c > index 48f7c7eb4dbc..faa01591df36 100644 > --- a/arch/x86/xen/mmu_pv.c > +++ b/arch/x86/xen/mmu_pv.c > @@ -1325,20 +1325,23 @@ static noinline void xen_flush_tlb(void) > preempt_enable(); > } > > -static void xen_flush_tlb_one_user(unsigned long addr) > +static void xen_flush_tlb_range(unsigned long start, unsigned long end, > + u8 stride_shift) > { > - struct mmuext_op *op; > - struct multicall_space mcs; > - > - trace_xen_mmu_flush_tlb_one_user(addr); > + struct mmuext_op op; > + unsigned long addr; > > preempt_disable(); > > - mcs = xen_mc_entry(sizeof(*op)); > - op = mcs.args; > - op->cmd = MMUEXT_INVLPG_LOCAL; > - op->arg1.linear_addr = addr & PAGE_MASK; > - MULTI_mmuext_op(mcs.mc, op, 1, NULL, DOMID_SELF); > + xen_mc_batch(); > + op.cmd = MMUEXT_INVLPG_LOCAL; > + > + trace_xen_mmu_flush_tlb_range(start, end, stride_shift); > + > + for (addr = start; addr < end; addr += 1ul << stride_shift) { > + op.arg1.linear_addr = addr & PAGE_MASK; > + xen_extend_mmuext_op(&op); > + } > > xen_mc_issue(PARAVIRT_LAZY_MMU); > > @@ -2394,7 +2397,7 @@ static const struct pv_mmu_ops xen_mmu_ops __initconst = { > > .flush_tlb_user = xen_flush_tlb, > .flush_tlb_kernel = xen_flush_tlb, > - .flush_tlb_one_user = xen_flush_tlb_one_user, > + .flush_tlb_range = xen_flush_tlb_range, > .flush_tlb_multi = xen_flush_tlb_multi, > .tlb_remove_table = tlb_remove_table, > > diff --git a/include/trace/events/xen.h b/include/trace/events/xen.h > index 546022acf160..32bf0a94b4d8 100644 > --- a/include/trace/events/xen.h > +++ b/include/trace/events/xen.h > @@ -352,14 +352,20 @@ DECLARE_EVENT_CLASS(xen_mmu_pgd, > DEFINE_XEN_MMU_PGD_EVENT(xen_mmu_pgd_pin); > DEFINE_XEN_MMU_PGD_EVENT(xen_mmu_pgd_unpin); > > -TRACE_EVENT(xen_mmu_flush_tlb_one_user, > - TP_PROTO(unsigned long addr), > - TP_ARGS(addr), > +TRACE_EVENT(xen_mmu_flush_tlb_range, > + TP_PROTO(unsigned long start, unsigned long end, > + unsigned char stride_shift), > + TP_ARGS(start, end, stride_shift), > TP_STRUCT__entry( > - __field(unsigned long, addr) > + __field(unsigned long, start) > + __field(unsigned long, end) > + __field(unsigned char, stride_shift) > ), > - TP_fast_assign(__entry->addr = addr), > - TP_printk("addr %lx", __entry->addr) > + TP_fast_assign(__entry->start = start; > + __entry->end = end; > + __entry->stride_shift = stride_shift), > + TP_printk("start %lx end %lx stride_shift %d", __entry->start, > + __entry->end, __entry->stride_shift) > ); > > TRACE_EVENT(xen_mmu_flush_tlb_multi, >