RE: [RFC PATCH v3 00/32] x86: enable FRED for x86-64

Li, Xin3
2023-02-28T07:30:32Z

I plan to remove RFC in the next round, any objection?

BTW, the KVM selftest failures Shan reported will be fixed with FRED KVM patch set, which is planned to be sent to LKML for review in March.

Thanks!
Xin

> -----Original Message-----
> From: Kang, Shan <shan.kang@intel.com>
> Sent: Friday, February 24, 2023 1:27 AM
> To: Li, Xin3 <xin3.li@intel.com>; kvm@vger.kernel.org; linux-
> kernel@vger.kernel.org; x86@kernel.org
> Cc: Christopherson,, Sean <seanjc@google.com>; bp@alien8.de;
> dave.hansen@linux.intel.com; peterz@infradead.org; hpa@zytor.com;
> mingo@redhat.com; tglx@linutronix.de; andrew.cooper3@citrix.com;
> pbonzini@redhat.com; Shankar, Ravi V <ravi.v.shankar@intel.com>
> Subject: Re: [RFC PATCH v3 00/32] x86: enable FRED for x86-64
>
> We tested the v3 FRED patch set on the Intel Simics® Simulator and a machine with
> a 7th Intel(R) Core(TM) CPU.
>
> Following are the LTP verion 20220121 test results on X86-64.
> +--------------------------------------------+-------+-------+-------+-------+
> | Config | Pass | Fail | Skip | Hang |
> +--------------------------------------------+-------+-------+-------+-------+
> | the 7th Intel(R) Core(TM) CPU | 1788 | 108 | 453 | 0 |
> | 6.2.0-rc7+ | | | | |
> +--------------------------------------------+-------+-------+-------+-------+
> | the 7th Intel(R) Core(TM) CPU | 1788 | 108 | 453 | 0 |
> | 6.2.0-rc7+ w/ FRED patch set | | | | |
> +--------------------------------------------+-------+-------+-------+-------+
> | Intel Simics® Simulator w/o FRED model | 1797 | 111 | 440 | 1 |
> | 6.2.0-rc7+ | | | | |
> +--------------------------------------------+-------+-------+-------+-------+
> | Intel Simics® Simulator w/o FRED model | 1797 | 111 | 440 | 1 |
> | 6.2.0-rc7+ w/ FRED patch set | | | | |
> +--------------------------------------------+-------+-------+-------+-------+
> | Intel Simics® Simulator w/ FRED model | 1797 | 111 | 440 | 1 |
> | 6.2.0-rc7+ | | | | |
> +--------------------------------------------+-------+-------+-------+-------+
> | Intel Simics® Simulator w/ FRED model | 1797 | 111 | 440 | 1 |
> | 6.2.0-rc7+ w/ FRED patch set FRED disabled | | | | |
> +--------------------------------------------+-------+-------+-------+-------+
> | Intel Simics® Simulator w/ FRED model | 1797 | 111 | 440 | 1 |
> | 6.2.0-rc7+ w/ FRED patch set | | | | |
> +--------------------------------------------+-------+-------+-------+-------+
> We were unable to identify any regression with the LTP tests.
>
> Following are the Kselftest results on X86-64.
> +--------------------------------------------+-------+-------+-------+-------+
> | Config | Pass | Fail | Skip | Hang |
> +--------------------------------------------+-------+-------+-------+-------+
> | the 7th Intel(R) Core(TM) CPU | 3224 | 454 | 591 | 5 |
> | 6.2.0-rc7+ | | | | |
> +--------------------------------------------+-------+-------+-------+-------+
> | the 7th Intel(R) Core(TM) CPU | 3224 | 454 | 591 | 5 |
> | 6.2.0-rc7+ w/ FRED patch set | | | | |
> +--------------------------------------------+-------+-------+-------+-------+
> | Intel Simics® Simulator w/o FRED model | 1853 | 267 | 2143 | 11 |
> | 6.2.0-rc7+ | | | | |
> +--------------------------------------------+-------+-------+-------+-------+
> | Intel Simics® Simulator w/o FRED model | 1853 | 267 | 2143 | 11 |
> | 6.2.0-rc7+ w/ FRED patch set | | | | |
> +--------------------------------------------+-------+-------+-------+-------+
> | Intel Simics® Simulator w/ FRED model | 1853 | 267 | 2143 | 11 |
> | 6.2.0-rc7+ | | | | |
> +--------------------------------------------+-------+-------+-------+-------+
> | Intel Simics® Simulator w/ FRED model | 1853 | 267 | 2143 | 11 |
> | 6.2.0-rc7+ w/ FRED patch set FRED disabled | | | | |
> +--------------------------------------------+-------+-------+-------+-------+
> | Intel Simics® Simulator w/ FRED model | 1847 | 272 | 2143 | 12 |
> | 6.2.0-rc7+ w/ FRED patch set | | | | |
> +--------------------------------------------+-------+-------+-------+-------+
> No regression was found on the bare metal, while the following are the regressions
> on the Simics® Simulator.
> +----------------------+----------------------+----------------------+
> | | Intel Simics® | Intel Simics® |
> | | Simulator w/ FRED | Simulator w/ FRED |
> | test name | model | model |
> | | 6.2.0-rc7+ w/ FRED | 6.2.0-rc7+ w/ FRED |
> | | patch set FRED | patch set |
> | | disabled | |
> +----------------------+----------------------+----------------------+
> | kvm:hyperv_clock | PASS | FAIL |
> +----------------------+----------------------+----------------------+
> | kvm:hyperv_features | PASS | FAIL |
> +----------------------+----------------------+----------------------+
> | kvm:xen_vmcall_test | PASS | FAIL |
> +----------------------+----------------------+----------------------+
> | kvm:hyperv_ipi | PASS | FAIL |
> +----------------------+----------------------+----------------------+
> | kvm:hyperv_tlb_flush | PASS | FAIL |
> +----------------------+----------------------+----------------------+
> | bpf:test_progs | FAIL | HANG |
> +----------------------+----------------------+----------------------+
> | x86:sysret_rip_64 | PASS | FAIL |
> +----------------------+----------------------+----------------------+
> The test "x86:sysret_rip_64" is NOT a valid test on FRED, and there is a fix from
> Ammar Faizi after we discussed it in the LKML. Other test failures are under
> investigation.
>
> FRED is a 64-bit only feature, however the 31st patch "x86/fred: allow dynamic
> stack frame size" applies to X86-32, thus we ran Kselftest and LTP on X86-32 to see
> if there is any regression, and we din't find any.
>
> Following are the Kselftest results on X86-32.
> +-------------------------------+---------+---------+---------+---------+
> | Config | Pass | Fail | Skip | Hang |
> +-------------------------------+---------+---------+---------+---------+
> | the 5th Intel(R) Core(TM) CPU | 1361 | 267 | 301 | 3 |
> | FRED 6.2.0-rc7+ | | | | |
> +-------------------------------+---------+---------+---------+---------+
> | the 5th Intel(R) Core(TM) CPU | 1361 | 267 | 301 | 3 |
> | 6.2.0-rc7+ w/ FRED patch set | | | | |
> +-------------------------------+---------+---------+---------+---------+
>
> Following are the LTP test results on X86-32.
> +-------------------------------+---------+---------+---------+---------+
> | Config | Pass | Fail | Skip | Hang |
> +-------------------------------+---------+---------+---------+---------+
> | the 5th Intel(R) Core(TM) CPU | 1849 | 81 | 419 | 0 |
> | 6.2.0-rc7+ w/ FRED patch set | | | | |
> +-------------------------------+---------+---------+---------+---------+
> | the 5th Intel(R) Core(TM) CPU | 1849 | 81 | 419 | 0 |
> | FRED 6.2.0-rc7+ | | | | |
> +-------------------------------+---------+---------+---------+---------+
>
> Thanks
> --Shan
>
> On Thu, 2023-02-23 at 23:01 -0800, Xin Li wrote:
> > This patch set enables FRED for x86-64, and it's based on the previous
> > LKGS patch set.
> >
> > The Intel flexible return and event delivery (FRED) architecture
> > defines simple new transitions that change privilege level (ring
> > transitions). The FRED architecture was designed with the following
> > goals:
> > 1) Improve overall performance and response time by replacing event
> > delivery through the interrupt descriptor table (IDT event delivery)
> > and event return by the IRET instruction with lower latency
> > transitions.
> > 2) Improve software robustness by ensuring that event delivery
> > establishes the full supervisor context and that event return
> > establishes the full user context.
> >
> > The new transitions defined by the FRED architecture are FRED event
> > delivery and, for returning from events, two FRED return instructions.
> > FRED event delivery can effect a transition from ring 3 to ring 0, but
> > it is used also to deliver events incident to ring 0. One FRED
> > instruction (ERETU) effects a return from ring 0 to ring 3, while the
> > other (ERETS) returns while remaining in ring 0.
> >
> > Search for the latest FRED spec in most search engines with this
> > search
> > pattern:
> >
> > site:intel.com FRED (flexible return and event delivery)
> > specification
> >
> > As of now there is no publicly avaiable CPU supporting FRED, thus the
> > Intel Simics® Simulator is used as software development and testing
> > vehicles. And it can be downloaded from:
> >
> > https://www.intel.com/content/www/us/en/developer/articles/tool/simics
> > -simulator.html
> >
> > To enable FRED, Simics package 8112 QSP-CPU needs to be installed with
> > CPU model configured as:
> > $cpu_comp_class = "x86-experimental-fred"
> >
> > Longer term, we should refactor common code shared by FRED and IDT
> > into common shared files, and contain IDT code using a new config
> CONFIG_X86_IDT.
> >
> > TODO: call external_interrupt() to reinject IRQ in KVM VMX.
> >
> > Changes since v2:
> > * Improve comments for changes in arch/x86/include/asm/idtentry.h.
> >
> > Changes since v1:
> > * call irqentry_nmi_{enter,exit}() in both IDT and FRED debug fault kernel
> > handler (Peter Zijlstra).
> > * Initialize a FRED exception handler to fred_bad_event() instead of NULL
> > if no FRED handler defined for an exception vector (Peter Zijlstra).
> > * Push calling irqentry_{enter,exit}() and instrumentation_{begin,end}()
> > down into individual FRED exception handlers, instead of in the dispatch
> > framework (Peter Zijlstra).
> >
> > H. Peter Anvin (Intel) (24):
> > x86/traps: let common_interrupt() handle IRQ_MOVE_CLEANUP_VECTOR
> > x86/traps: add a system interrupt table for system interrupt dispatch
> > x86/traps: add external_interrupt() to dispatch external interrupts
> > x86/cpufeature: add the cpu feature bit for FRED
> > x86/opcode: add ERETU, ERETS instructions to x86-opcode-map
> > x86/objtool: teach objtool about ERETU and ERETS
> > x86/cpu: add X86_CR4_FRED macro
> > x86/fred: add Kconfig option for FRED (CONFIG_X86_FRED)
> > x86/fred: if CONFIG_X86_FRED is disabled, disable FRED support
> > x86/cpu: add MSR numbers for FRED configuration
> > x86/fred: header file with FRED definitions
> > x86/fred: make unions for the cs and ss fields in struct pt_regs
> > x86/fred: reserve space for the FRED stack frame
> > x86/fred: add a page fault entry stub for FRED
> > x86/fred: add a debug fault entry stub for FRED
> > x86/fred: add a NMI entry stub for FRED
> > x86/fred: FRED entry/exit and dispatch code
> > x86/fred: FRED initialization code
> > x86/fred: update MSR_IA32_FRED_RSP0 during task switch
> > x86/fred: let ret_from_fork() jmp to fred_exit_user when FRED is
> > enabled
> > x86/fred: disallow the swapgs instruction when FRED is enabled
> > x86/fred: no ESPFIX needed when FRED is enabled
> > x86/fred: allow single-step trap and NMI when starting a new thread
> > x86/fred: allow FRED systems to use interrupt vectors 0x10-0x1f
> >
> > Xin Li (8):
> > x86/traps: add install_system_interrupt_handler()
> > x86/traps: export external_interrupt() for VMX IRQ reinjection
> > x86/fred: header file for event types
> > x86/fred: add a machine check entry stub for FRED
> > x86/fred: fixup fault on ERETU by jumping to fred_entrypoint_user
> > x86/ia32: do not modify the DPL bits for a null selector
> > x86/fred: allow dynamic stack frame size
> > x86/fred: disable FRED by default in its early stage
> >
> > .../admin-guide/kernel-parameters.txt | 4 +
> > arch/x86/Kconfig | 9 +
> > arch/x86/entry/Makefile | 5 +-
> > arch/x86/entry/entry_32.S | 2 +-
> > arch/x86/entry/entry_64.S | 5 +
> > arch/x86/entry/entry_64_fred.S | 59 +++++
> > arch/x86/entry/entry_fred.c | 234 ++++++++++++++++++
> > arch/x86/entry/vsyscall/vsyscall_64.c | 2 +-
> > arch/x86/include/asm/cpufeatures.h | 1 +
> > arch/x86/include/asm/disabled-features.h | 8 +-
> > arch/x86/include/asm/entry-common.h | 3 +
> > arch/x86/include/asm/event-type.h | 17 ++
> > arch/x86/include/asm/extable_fixup_types.h | 4 +-
> > arch/x86/include/asm/fred.h | 131 ++++++++++
> > arch/x86/include/asm/idtentry.h | 76 +++++-
> > arch/x86/include/asm/irq.h | 5 +
> > arch/x86/include/asm/irq_vectors.h | 15 +-
> > arch/x86/include/asm/msr-index.h | 13 +-
> > arch/x86/include/asm/processor.h | 12 +-
> > arch/x86/include/asm/ptrace.h | 36 ++-
> > arch/x86/include/asm/switch_to.h | 10 +-
> > arch/x86/include/asm/thread_info.h | 35 +--
> > arch/x86/include/asm/traps.h | 13 +
> > arch/x86/include/asm/vmx.h | 17 +-
> > arch/x86/include/uapi/asm/processor-flags.h | 2 +
> > arch/x86/kernel/Makefile | 1 +
> > arch/x86/kernel/apic/apic.c | 11 +-
> > arch/x86/kernel/apic/vector.c | 8 +-
> > arch/x86/kernel/cpu/acrn.c | 7 +-
> > arch/x86/kernel/cpu/common.c | 88 ++++---
> > arch/x86/kernel/cpu/mce/core.c | 11 +
> > arch/x86/kernel/cpu/mshyperv.c | 22 +-
> > arch/x86/kernel/espfix_64.c | 8 +
> > arch/x86/kernel/fred.c | 73 ++++++
> > arch/x86/kernel/head_32.S | 3 +-
> > arch/x86/kernel/idt.c | 6 +-
> > arch/x86/kernel/irq.c | 6 +-
> > arch/x86/kernel/irqinit.c | 7 +-
> > arch/x86/kernel/kvm.c | 4 +-
> > arch/x86/kernel/nmi.c | 28 +++
> > arch/x86/kernel/process.c | 5 +
> > arch/x86/kernel/process_64.c | 21 +-
> > arch/x86/kernel/signal_32.c | 21 +-
> > arch/x86/kernel/traps.c | 175 +++++++++++--
> > arch/x86/lib/x86-opcode-map.txt | 2 +-
> > arch/x86/mm/extable.c | 28 +++
> > arch/x86/mm/fault.c | 20 +-
> > drivers/xen/events/events_base.c | 5 +-
> > kernel/fork.c | 6 +
> > tools/arch/x86/include/asm/cpufeatures.h | 1 +
> > .../arch/x86/include/asm/disabled-features.h | 8 +-
> > tools/arch/x86/include/asm/msr-index.h | 13 +-
> > tools/arch/x86/lib/x86-opcode-map.txt | 2 +-
> > tools/objtool/arch/x86/decode.c | 22 +-
> > 54 files changed, 1156 insertions(+), 174 deletions(-) create mode
> > 100644 arch/x86/entry/entry_64_fred.S create mode 100644
> > arch/x86/entry/entry_fred.c create mode 100644
> > arch/x86/include/asm/event-type.h create mode 100644
> > arch/x86/include/asm/fred.h create mode 100644 arch/x86/kernel/fred.c
> >