From: "H. Peter Anvin" <hpa@zytor.com>
To: Lai Jiangshan <laijs@linux.alibaba.com>,
Lai Jiangshan <jiangshanlai@gmail.com>,
linux-kernel@vger.kernel.org
Cc: Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
x86@kernel.org, Joerg Roedel <jroedel@suse.de>,
Youquan Song <youquan.song@intel.com>,
Tony Luck <tony.luck@intel.com>, Juergen Gross <jgross@suse.com>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>
Subject: Re: [PATCH 17/24] x86/entry: Introduce struct ist_regs
Date: Thu, 09 Sep 2021 21:51:55 -0700 [thread overview]
Message-ID: <4C8A910F-679F-4F49-AAA5-AA3B9BE5F2BD@zytor.com> (raw)
In-Reply-To: <286DCB70-B36E-4229-966E-BE45F2AEA703@zytor.com>
Note: with FRED paranoid entry is no longer needed since the hardware enforces gs_base mode consistency.
On September 9, 2021 9:50:40 PM PDT, "H. Peter Anvin" <hpa@zytor.com> wrote:
>It may affect your design, I don't know, but FRED exception delivery (as currently architected per draft 2.0; it is subject to change still) pushes several fields above the conventional stack frame (and thus above pt_regs.)
>
>On September 9, 2021 5:18:47 PM PDT, Lai Jiangshan <laijs@linux.alibaba.com> wrote:
>>
>>
>>On 2021/9/1 01:50, Lai Jiangshan wrote:
>>> From: Lai Jiangshan <laijs@linux.alibaba.com>
>>>
>>> struct ist_regs is the upmost stack frame for IST interrupt, it
>>> consists of struct pt_regs and other fields which will be added in
>>> later patch.
>>>
>>> Make vc_switch_off_ist() take ist_regs as its argument and it will switch
>>> the whole ist_regs if needed.
>>>
>>> Make the frame before calling paranoid_entry() and paranoid_exit() be
>>> struct ist_regs.
>>>
>>> This patch is prepared for converting paranoid_entry() and paranoid_exit()
>>> into C code which will need the additinal fields to store the results in
>>> paranoid_entry() and to use them in paranoid_exit().
>>
>>This patch was over designed.
>>
>>In ASM code, we can easily save results in the callee-saved registers.
>>For example, rc3 is saved in %r14, gsbase info is saved in %rbx.
>>
>>And in C code, we can't save results in registers. And I thought there was
>>no place to save the results because the CR3 and gsbase are not kernel's.
>>So I extended the pt_regs to ist_regs to save the results.
>>
>>But it was incorrect. The results can be saved in percpu data at the end of
>>paranoid_entry() after the CR3/gsbase are settled down. And the results
>>can be read at the beginning of paranoid_exit() before the CR3/gsbase are
>>switched to the interrupted context's.
>>
>>sigh.
>>
>>>
>>> The C interrupt handlers don't use struct ist_regs due to they don't need
>>> the additional fields in the struct ist_regs, and they still use pt_regs.
>>>
>>
>
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
next prev parent reply other threads:[~2021-09-10 4:52 UTC|newest]
Thread overview: 72+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-31 17:50 [PATCH 00/24] x86/entry/64: Convert a bunch of ASM entry code into C code Lai Jiangshan
2021-08-31 17:50 ` [PATCH 01/24] x86/traps: Remove stack-protector from traps.c Lai Jiangshan
2021-08-31 17:50 ` [PATCH 02/24] x86/traps: Move arch/x86/kernel/traps.c to arch/x86/entry/ Lai Jiangshan
2021-09-02 8:09 ` Joerg Roedel
2021-09-02 9:21 ` Lai Jiangshan
2021-09-02 10:50 ` Peter Zijlstra
2021-09-02 11:54 ` Lai Jiangshan
2021-09-02 12:05 ` Peter Zijlstra
2021-09-02 13:34 ` Peter Zijlstra
2021-09-02 17:05 ` Nick Desaulniers
2021-09-02 17:19 ` Miguel Ojeda
2021-09-02 17:23 ` Nick Desaulniers
2021-09-03 7:36 ` Martin Liška
2021-09-07 21:12 ` Nick Desaulniers
2021-09-08 7:33 ` Martin Liška
2021-08-31 17:50 ` [PATCH 03/24] x86/traps: Move declaration of native_irq_return_iret up Lai Jiangshan
2021-08-31 17:50 ` [PATCH 04/24] x86/entry: Expose the address of .Lgs_change to traps.c Lai Jiangshan
2021-09-02 9:14 ` Peter Zijlstra
2021-09-02 9:20 ` Lai Jiangshan
2021-08-31 17:50 ` [PATCH 05/24] x86/entry: Introduce __entry_text for entry code written in C Lai Jiangshan
2021-08-31 19:34 ` Peter Zijlstra
2021-09-01 0:23 ` Lai Jiangshan
2021-08-31 17:50 ` [PATCH 06/24] x86/entry: Move PTI_USER_* to arch/x86/include/asm/processor-flags.h Lai Jiangshan
2021-08-31 17:50 ` [PATCH 07/24] x86: Mark __native_read_cr3() & native_write_cr3() as __always_inline Lai Jiangshan
2021-08-31 17:50 ` [PATCH 08/24] x86/traps: Add C verion of SWITCH_TO_KERNEL_CR3 as switch_to_kernel_cr3() Lai Jiangshan
2021-08-31 17:50 ` [PATCH 09/24] x86/traps: Add fence_swapgs_{user,kernel}_entry() Lai Jiangshan
2021-09-02 9:25 ` Peter Zijlstra
2021-08-31 17:50 ` [PATCH 10/24] x86/traps: Move pt_regs only in fixup_bad_iret() Lai Jiangshan
2021-08-31 17:50 ` [PATCH 11/24] x86/entry: Replace the most of asm code of error_entry to C code Lai Jiangshan
2021-09-02 10:16 ` Peter Zijlstra
2021-09-02 12:08 ` Lai Jiangshan
2021-08-31 17:50 ` [PATCH 12/24] x86/traps: Reconstruct pt_regs on task stack directly in fixup_bad_iret() Lai Jiangshan
2021-08-31 17:50 ` [PATCH 13/24] x86/traps: Mark sync_regs() and fixup_bad_iret() as static __always_inline Lai Jiangshan
2021-08-31 17:50 ` [PATCH 14/24] x86/entry: Make paranoid_exit() callable Lai Jiangshan
2021-08-31 17:50 ` [PATCH 15/24] x86/entry: Call paranoid_exit() in asm_exc_nmi() Lai Jiangshan
2021-08-31 17:50 ` [PATCH 16/24] x86/entry: Use skip_rdi instead of save_ret for PUSH_AND_CLEAR_REGS Lai Jiangshan
2021-08-31 17:50 ` [PATCH 17/24] x86/entry: Introduce struct ist_regs Lai Jiangshan
2021-09-10 0:18 ` Lai Jiangshan
2021-09-10 0:36 ` Lai Jiangshan
2021-09-10 4:31 ` H. Peter Anvin
2021-09-10 7:13 ` Lai Jiangshan
2021-09-10 7:14 ` H. Peter Anvin
2021-09-10 4:50 ` H. Peter Anvin
2021-09-10 4:51 ` H. Peter Anvin [this message]
2021-08-31 17:50 ` [PATCH 18/24] x86/entry: Add the C version ist_switch_to_kernel_cr3() Lai Jiangshan
2021-08-31 17:50 ` [PATCH 19/24] x86/entry: Add the C version ist_restore_cr3() Lai Jiangshan
2021-08-31 17:50 ` [PATCH 20/24] x86/entry: Add the C version get_percpu_base() Lai Jiangshan
2021-08-31 17:50 ` [PATCH 21/24] x86/entry: Add the C version ist_switch_to_kernel_gsbase() Lai Jiangshan
2021-08-31 17:50 ` [PATCH 22/24] x86/entry: Implement and use do_paranoid_entry() and paranoid_exit() Lai Jiangshan
2021-09-02 10:33 ` Peter Zijlstra
2021-09-02 10:42 ` Lai Jiangshan
2021-09-02 12:02 ` Peter Zijlstra
2021-09-02 11:58 ` Lai Jiangshan
2021-09-02 12:29 ` Joerg Roedel
2021-08-31 17:50 ` [PATCH 23/24] x86/entry: Remove the unused ASM macros Lai Jiangshan
2021-08-31 17:50 ` [PATCH 24/24] x86/syscall/64: Move the checking for sysret to C code Lai Jiangshan
2021-09-10 7:20 ` Nikolay Borisov
2021-09-10 7:30 ` Lai Jiangshan
2021-08-31 20:44 ` [PATCH 00/24] x86/entry/64: Convert a bunch of ASM entry code into " Peter Zijlstra
2021-09-02 6:28 ` Lai Jiangshan
2021-09-02 7:44 ` Peter Zijlstra
2021-09-02 10:50 ` [PATCH 25/24] x86/traps: Rewrite native_load_gs_index in " Lai Jiangshan
2021-09-08 1:38 ` H. Peter Anvin
2021-09-08 4:42 ` H. Peter Anvin
2021-09-08 5:00 ` H. Peter Anvin
2021-09-08 7:12 ` Lai Jiangshan
2021-09-09 23:16 ` H. Peter Anvin
2021-09-13 20:01 ` Andy Lutomirski
2021-09-14 2:04 ` Lai Jiangshan
2021-09-14 8:14 ` Peter Zijlstra
2021-09-14 8:17 ` Borislav Petkov
2021-09-14 8:40 ` Lai Jiangshan
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