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([2600:1011:b01e:e4d1:54df:ba07:cac1:aeab]) by smtp.gmail.com with ESMTPSA id n9-v6sm19468348pgp.42.2018.07.12.13.53.21 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 12 Jul 2018 13:53:21 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (1.0) Subject: Re: [PATCH 05/39] x86/entry/32: Unshare NMI return path From: Andy Lutomirski X-Mailer: iPhone Mail (15F79) In-Reply-To: <1531308586-29340-6-git-send-email-joro@8bytes.org> Date: Thu, 12 Jul 2018 13:53:19 -0700 Cc: Thomas Gleixner , Ingo Molnar , "H . Peter Anvin" , x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Linus Torvalds , Andy Lutomirski , Dave Hansen , Josh Poimboeuf , Juergen Gross , Peter Zijlstra , Borislav Petkov , Jiri Kosina , Boris Ostrovsky , Brian Gerst , David Laight , Denys Vlasenko , Eduardo Valentin , Greg KH , Will Deacon , aliguori@amazon.com, daniel.gruss@iaik.tugraz.at, hughd@google.com, keescook@google.com, Andrea Arcangeli , Waiman Long , Pavel Machek , "David H . Gutteridge" , jroedel@suse.de Content-Transfer-Encoding: 7bit Message-Id: References: <1531308586-29340-1-git-send-email-joro@8bytes.org> <1531308586-29340-6-git-send-email-joro@8bytes.org> To: Joerg Roedel Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Jul 11, 2018, at 4:29 AM, Joerg Roedel wrote: > > From: Joerg Roedel > > NMI will no longer use most of the shared return path, > because NMI needs special handling when the CR3 switches for > PTI are added. Why? What would go wrong? How many return-to-usermode paths will we have? 64-bit has only one. > This patch prepares for that. > > Signed-off-by: Joerg Roedel > --- > arch/x86/entry/entry_32.S | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S > index d35a69a..571209e 100644 > --- a/arch/x86/entry/entry_32.S > +++ b/arch/x86/entry/entry_32.S > @@ -1017,7 +1017,7 @@ ENTRY(nmi) > > /* Not on SYSENTER stack. */ > call do_nmi > - jmp .Lrestore_all_notrace > + jmp .Lnmi_return > > .Lnmi_from_sysenter_stack: > /* > @@ -1028,7 +1028,11 @@ ENTRY(nmi) > movl PER_CPU_VAR(cpu_current_top_of_stack), %esp > call do_nmi > movl %ebx, %esp > - jmp .Lrestore_all_notrace > + > +.Lnmi_return: > + CHECK_AND_APPLY_ESPFIX > + RESTORE_REGS 4 > + jmp .Lirq_return > > #ifdef CONFIG_X86_ESPFIX32 > .Lnmi_espfix_stack: > -- > 2.7.4 >