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Date: Tue, 16 Jun 2020 09:56:00 +0800 From: Lai Jiangshan <jiangshanlai+lkml@...il.com> To: Andy Lutomirski <luto@...nel.org> Cc: Lai Jiangshan <laijs@...ux.alibaba.com>, LKML <linux-kernel@...r.kernel.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, X86 ML <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>, Peter Zijlstra <peterz@...radead.org>, Alexandre Chartre <alexandre.chartre@...cle.com>, "Eric W. Biederman" <ebiederm@...ssion.com>, Jann Horn <jannh@...gle.com>, Dave Hansen <dave.hansen@...ux.intel.com> Subject: Re: [PATCH V2 0/4] x86/entry: simply stack switching when exception on userspace On Sat, May 30, 2020 at 2:33 AM Andy Lutomirski <luto@...nel.org> wrote: > > On Fri, May 29, 2020 at 1:26 AM Lai Jiangshan <laijs@...ux.alibaba.com> wrote: > > > > 7f2590a110b8("x86/entry/64: Use a per-CPU trampoline stack for IDT entries") > > has resulted that when exception on userspace, the kernel (error_entry) > > always push the pt_regs to entry stack(sp0), and then copy them to the > > kernel stack. > > > > And recent x86/entry work makes interrupt also use idtentry > > and makes all the interrupt code save the pt_regs on the sp0 stack > > and then copy it to the thread stack like exception. > > > > This is hot path (page fault, ipi), such overhead should be avoided. > > And the original interrupt_entry directly switches to kernel stack > > and pushes pt_regs to kernel stack. We should do it for error_entry. > > This is the job of patch1. > > > > Patch 2-4 simply stack switching for .Lerror_bad_iret by just doing > > all the work in one function (fixup_bad_iret()). > > > > The patch set is based on tip/x86/entry (28447ea41542) (May 20). > > There are definitely good cleanups in here, but I think it would be > nice rebased to whatever lands in 5.8-rc1 settles. > Hello, All This patchset can be smoothly applicable to the newest tip/x86/entry which has 5.8-rc1 merged. Which means I don't have to respin/resend it until any update is needed. Could you have a review on it please. Thanks Lai
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