Re: [PATCH v5 00/34] x86: enable FRED for x86-64

From: Kang, Shan
Date: Mon Mar 20 2023 - 03:41:01 EST

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We wanted to check whether there are KVM regressions with the v5 FRED patch set,
and had a round of Kselftest on KVM guests.
Following are the results on X86-64.

+--------------------------------+-------+-------+-------+-------+
| Config | Pass | Fail | Skip | Hang |
+--------------------------------+-------+-------+-------+-------+
| the 7th Intel(R) Core(TM) CPU | | | | |
| | host 6.3.0-rc1+ w/ FRED | 2720 | 403 | 689 | 9 |
| patch set FRED disabled | | | | | |
| guest 6.3.0-rc1+ | | | | |
+--------------------------------+-------+-------+-------+-------+
| the 7th Intel(R) Core(TM) CPU | | | | |
| | host 6.3.0-rc1+ w/ FRED | 2720 | 403 | 689 | 9 |
| patch set | guest 6.3.0-rc1+ | | | | |
+--------------------------------+-------+-------+-------+-------+
| Intel Simics® Simulator w/o | | | | |
| FRED model | host 6.3.0-rc1+ | | 1403 | 277 | 2127 | 14 |
| guest 6.3.0-rc1+ | | | | |
+--------------------------------+-------+-------+-------+-------+
| Intel Simics® Simulator w/o | | | | |
| FRED model | host 6.3.0-rc1+ | | | | |
| w/ FRED patch set | guest | 1403 | 277 | 2127 | 14 |
| 6.3.0-rc1+ w/ FRED patch set | | | | |
| FRED disabled | | | | |
+--------------------------------+-------+-------+-------+-------+
| Intel Simics® Simulator w/o | | | | |
| FRED model | host 6.3.0-rc1+ | 1403 | 277 | 2127 | 14 |
| w/ FRED patch set | guest | | | | |
| 6.3.0-rc1+ w/ FRED patch set | | | | |
+--------------------------------+-------+-------+-------+-------+
| Intel Simics® Simulator w/ | | | | |
| FRED model + host 6.3.0-rc1+ | | 1404 | 276 | 2127 | 14 |
| guest 6.3.0-rc1+ w/ FRED patch | | | | |
| set | | | | |
+--------------------------------+-------+-------+-------+-------+
| Intel Simics® Simulator w/ | | | | |
| FRED model | host 6.3.0-rc1+ | 1404 | 276 | 2127 | 14 |
| w/ FRED patch set FRED | | | | |
| disabled | guest 6.3.0-rc1+ | | | | |
+--------------------------------+-------+-------+-------+-------+
| Intel Simics® Simulator w/ | | | | |
| FRED model | host 6.3.0-rc1+ | | | | |
| w/ FRED patch set FRED | 1404 | 276 | 2127 | 14 |
| disabled | guest 6.3.0-rc1+ w/ | | | | |
| FRED patch set | | | | |
+--------------------------------+-------+-------+-------+-------+
| Intel Simics® Simulator w/ | | | | |
| FRED model | host 6.3.0-rc1+ | 1404 | 276 | 2127 | 14 |
| w/ FRED patch set | guest | | | | |
| 6.3.0-rc1+ | | | | |
+--------------------------------+-------+-------+-------+-------+
| Intel Simics® Simulator w/ | | | | |
| FRED model | host 6.3.0-rc1+ | | | | |
| w/ FRED patch set | guest | 1404 | 276 | 2127 | 14 |
| 6.3.0-rc1+ w/ FRED patch set | | | | |
| FRED disabled | | | | |
+--------------------------------+-------+-------+-------+-------+
| Intel Simics® Simulator w/ | | | | |
| FRED model | host 6.3.0-rc1+ | 1404 | 276 | 2127 | 14 |
| w/ FRED patch set | guest | | | | |
| 6.3.0-rc1+ w/ FRED patch set | | | | |
+--------------------------------+-------+-------+-------+-------+

The Simics FRED model has one more passed case, which is x86:test_vsyscall_32,
due to https://lore.kernel.org/lkml/20230311084824.2340-1-xin3.li@xxxxxxxxx/.

Thanks
--Shan

On Sat, 2023-03-11 at 09:58 +0000, Kang, Shan wrote:
> We tested the v5 FRED patch set on the Intel Simics® Simulator and a machine
> with a 7th Intel(R) Core(TM) CPU.
>
> Following are the Kselftest results on X86-64.
> +--------------------------------------------+-------+-------+-------+-------+
> > Config | Pass | Fail | Skip | Hang |
> +--------------------------------------------+-------+-------+-------+-------+
> > the 7th Intel(R) Core(TM) CPU | 3078 | 458 | 734 | 5 |
> > 6.3.0-rc1+ | | | | |
> +--------------------------------------------+-------+-------+-------+-------+
> > the 7th Intel(R) Core(TM) CPU | 3078 | 458 | 734 | 5 |
> > 6.3.0-rc1+ w/ FRED patch set | | | | |
> +--------------------------------------------+-------+-------+-------+-------+
> > Intel Simics® Simulator w/o FRED model | 1888 | 271 | 2105 | 11 |
> > 6.3.0-rc1+ | | | | |
> +--------------------------------------------+-------+-------+-------+-------+
> > Intel Simics® Simulator w/o FRED model | 1888 | 271 | 2105 | 11 |
> > 6.3.0-rc1+ w/ FRED patch set | | | | |
> +--------------------------------------------+-------+-------+-------+-------+
> > Intel Simics® Simulator w/ FRED model | 1889 | 270 | 2105 | 11 |
> > 6.3.0-rc1+ | | | | |
> +--------------------------------------------+-------+-------+-------+-------+
> > Intel Simics® Simulator w/ FRED model | 1889 | 270 | 2105 | 11 |
> > 6.3.0-rc1+ w/ FRED patch set FRED disabled | | | | |
> +--------------------------------------------+-------+-------+-------+-------+
> > Intel Simics® Simulator w/ FRED model | 1888 | 270 | 2105 | 12 |
> > 6.3.0-rc1+ w/ FRED patch set | | | | |
> +--------------------------------------------+-------+-------+-------+-------+
>
> The following issues are seen in this round of test.
> +----------------+----------------+----------------+----------------+
> > | x86:test_ | bpf:test_progs | x86:sysret |
> > | vsyscall_32 | | _rip_64 |
> +----------------+----------------+----------------+----------------+
> > the 7th | | | |
> > Intel(R) | FAIL | FAIL | PASS |
> > Core(TM) CPU | | | |
> > 6.3.0-rc1+ | | | |
> +----------------+----------------+----------------+----------------+
> > the 7th | | | |
> > Intel(R) | | | |
> > Core(TM) CPU | FAIL | FAIL | PASS |
> > 6.3.0-rc1+ w/ | | | |
> > FRED patch set | | | |
> +----------------+----------------+----------------+----------------+
> > Intel Simics® | | | |
> > Simulator w/o | FAIL | FAIL | PASS |
> > FRED model | | | |
> > 6.3.0-rc1+ | | | |
> +----------------+----------------+----------------+----------------+
> > Intel Simics® | | | |
> > Simulator w/o | | | |
> > FRED model | FAIL | FAIL | PASS |
> > 6.3.0-rc1+ w/ | | | |
> > FRED patch set | | | |
> +----------------+----------------+----------------+----------------+
> > Intel Simics® | | | |
> > Simulator w/ | PASS | FAIL | PASS |
> > FRED model | | | |
> > 6.3.0-rc1+ | | | |
> +----------------+----------------+----------------+----------------+
> > Intel Simics® | | | |
> > Simulator w/ | | | |
> > FRED model | PASS | FAIL | PASS |
> > 6.3.0-rc1+ w/ | | | |
> > FRED patch set | | | |
> > FRED disabled | | | |
> +----------------+----------------+----------------+----------------+
> > Intel Simics® | | | |
> > Simulator w/ | | | |
> > FRED model | PASS | HANG | FAIL |
> > 6.3.0-rc1+ w/ | | | |
> > FRED patch set | | | |
> +----------------+----------------+----------------+----------------+
>
> 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.
>
> The test "bpf:test_progs" is still in investigation.
>
> The "x86:test_vsyscall_32" is a regression since the v3 FRED patch set.
>
> Thanks
> --Shan
>
> On Mon, 2023-03-06 at 18:39 -0800, Xin Li wrote:
> > This patch set enables FRED for x86-64.
> >
> > 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, the 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.
> >
> > Changes since v4:
> > * Rebased against v6.3-rc1.
> > * Do NOT use the term "injection", which in the KVM context means to
> > reinject an event into the guest (Sean Christopherson).
> > * Add the explanation of why to execute "int $2" to invoke the NMI handler
> > in NMI caused VM exits (Sean Christopherson).
> > * Use cs/ss instead of csx/ssx when initializing the pt_regs structure
> > for calling external_interrupt(), otherwise it breaks i386 build.
> >
> > Changes since v3:
> > * Call external_interrupt() to handle IRQ in IRQ caused VM exits.
> > * Execute "int $2" to handle NMI in NMI caused VM exits.
> > * Rename csl/ssl of the pt_regs structure to csx/ssx (x for extended)
> > (Andrew Cooper).
> >
> > 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 (10):
> > 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
> > KVM: x86/vmx: call external_interrupt() to handle IRQ in IRQ caused VM
> > exits
> > KVM: x86/vmx: execute "int $2" to handle NMI in NMI caused VM exits
> > when FRED is enabled
> >
> > .../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/kvm/vmx/vmx.c | 33 ++-
> > 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 | 19 +-
> > 55 files changed, 1185 insertions(+), 175 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
> >

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