Re: [PATCH V4 0/6] x86: Don't abuse tss.sp1

From: mark gross <mgross@linux.intel.com>
To: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: linux-kernel@vger.kernel.org, Borislav Petkov <bp@alien8.de>,
	Lai Jiangshan <laijs@linux.alibaba.com>,
	Andy Lutomirski <luto@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Vincenzo Frascino <vincenzo.frascino@arm.com>,
	Joerg Roedel <jroedel@suse.de>,
	Ricardo Neri <ricardo.neri-calderon@linux.intel.com>,
	Reinette Chatre <reinette.chatre@intel.com>,
	Balbir Singh <sblbir@amazon.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Gabriel Krisman Bertazi <krisman@collabora.com>,
	Kees Cook <keescook@chromium.org>,
	Frederic Weisbecker <frederic@kernel.org>,
	Jens Axboe <axboe@kernel.dk>,
	Arvind Sankar <nivedita@alum.mit.edu>,
	Brian Gerst <brgerst@gmail.com>, Ard Biesheuvel <ardb@kernel.org>,
	Andi Kleen <ak@linux.intel.com>, Mike Rapoport <rppt@kernel.org>,
	Mike Hommey <mh@glandium.org>,
	Mark Gross <mgross@linux.intel.com>,
	Fenghua Yu <fenghua.yu@intel.com>,
	Tony Luck <tony.luck@intel.com>,
	Anthony Steinhauser <asteinhauser@google.com>,
	Jay Lang <jaytlang@mit.edu>,
	"Chang S. Bae" <chang.seok.bae@intel.com>
Subject: Re: [PATCH V4 0/6] x86: Don't abuse tss.sp1
Date: Wed, 10 Feb 2021 15:42:28 -0800	[thread overview]
Message-ID: <20210210234228.GB75203@linux.intel.com> (raw)
In-Reply-To: <20210210133917.2414-1-jiangshanlai@gmail.com>

On Wed, Feb 10, 2021 at 09:39:11PM +0800, Lai Jiangshan wrote:
> From: Lai Jiangshan <laijs@linux.alibaba.com>
> 
> In x86_64, tss.sp1 is reused as cpu_current_top_of_stack.  We'd better
> directly use percpu since CR3 and gs_base is correct when it is used.
Be more direct if not using percpu is incorrect in some way.
> 
> In x86_32, tss.sp1 is resued as thread.sp0 in three places in entry
s/resued/reused
> code.  We have the correct CR3 and %fs at two of the places.  The last
> one is sysenter.  This patchset makes %fs available earlier so that
> we can also use percpu in sysenter.  And add a percpu cpu_current_thread_sp0
> for thread.sp0 instead of tss.sp1
> 
> [V3]: https://lore.kernel.org/lkml/20210127163231.12709-1-jiangshanlai@gmail.com/
> [V2]: https://lore.kernel.org/lkml/20210125173444.22696-1-jiangshanlai@gmail.com/
> [V1]: https://lore.kernel.org/lkml/20210123084900.3118-1-jiangshanlai@gmail.com/
> 
> Changed from V3:
> 	Update subjects as Borislav's imperative request. ^_^
> 	Update changelog as Borislav suggested.
> 	Change EXPORT_PER_CPU_SYMBOL to EXPORT_PER_CPU_SYMBOL_GPL.
> 
> Changed from V2:
> 	Add missing "%ss:" reported by Brian Gerst.
> 
> Changed from V1:
> 	Requested from Andy to also fix sp1 for x86_32.
> 	Update comments in the x86_64 patch as Andy sugguested.
> 
> Lai Jiangshan (6):
>   x86/entry/64: Move cpu_current_top_of_stack out of TSS
>   x86/entry/32: Use percpu instead of offset-calculation to get
>     thread.sp0 in SWITCH_TO_KERNEL_STACK
>   x86/entry/32: Switch to the task stack without emptying the entry
>     stack
>   x86/entry/32: Restore %fs before switching stack
>   x86/entry/32: Use percpu to get thread.sp0 in SYSENTER
>   x86/entry/32: Introduce cpu_current_thread_sp0 to replace
>     cpu_tss_rw.x86_tss.sp1
> 
>  arch/x86/entry/entry_32.S          | 38 +++++++++++++++++-------------
>  arch/x86/include/asm/processor.h   | 12 ++--------
>  arch/x86/include/asm/switch_to.h   |  8 +------
>  arch/x86/include/asm/thread_info.h |  6 -----
>  arch/x86/kernel/asm-offsets.c      |  1 -
>  arch/x86/kernel/asm-offsets_32.c   | 10 --------
>  arch/x86/kernel/cpu/common.c       | 12 +++++++++-
>  arch/x86/kernel/process.c          |  7 ------
>  arch/x86/mm/pti.c                  |  7 +++---
>  9 files changed, 39 insertions(+), 62 deletions(-)
> 
> -- 
> 2.19.1.6.gb485710b
>