From: Demi Marie Obenour <demiobenour@gmail.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>,
Xen-devel <xen-devel@lists.xenproject.org>
Cc: "Jan Beulich" <JBeulich@suse.com>,
"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [PATCH v3 05/22] x86/fsgsbase: Improve code generation in read_registers()
Date: Fri, 3 Oct 2025 20:13:26 -0400 [thread overview]
Message-ID: <e64f2529-9e39-47a4-949a-eacb07a2bb06@gmail.com> (raw)
In-Reply-To: <20251003225334.2123667-6-andrew.cooper3@citrix.com>
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On 10/3/25 18:53, Andrew Cooper wrote:
> It turns out that using the higher level helpers adjacent like this leads to
> terrible code generation. Due to -fno-strict-alising, the store into state->
> invalidates the read_cr4() address calculation (which is really cpu_info->cr4
> under the hood), meaning that it can't be hoisted.
It would be nice if compilers could warn when they
could not optimize because of something like this.
--
Sincerely,
Demi Marie Obenour (she/her/hers)
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next prev parent reply other threads:[~2025-10-04 0:13 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-03 22:53 [PATCH v3 for-4.21 00/22] x86: FRED support Andrew Cooper
2025-10-03 22:53 ` [PATCH v3 01/22] x86/msr: Change rdmsr() to have normal API Andrew Cooper
2025-10-07 15:47 ` Jan Beulich
2025-10-03 22:53 ` [PATCH v3 02/22] x86/msr: Change wrmsr() to take a single parameter Andrew Cooper
2025-10-04 0:11 ` Demi Marie Obenour
2025-10-04 0:14 ` Andrew Cooper
2025-10-03 22:53 ` [PATCH v3 03/22] x86/fsgsbase: Split out __{rd,wr}gs_shadow() helpers Andrew Cooper
2025-10-07 15:49 ` Jan Beulich
2025-10-03 22:53 ` [PATCH v3 04/22] x86/fsgsbase: Update fs/gs helpers to use wrmsrns() Andrew Cooper
2025-10-07 15:53 ` Jan Beulich
2025-10-03 22:53 ` [PATCH v3 05/22] x86/fsgsbase: Improve code generation in read_registers() Andrew Cooper
2025-10-04 0:13 ` Demi Marie Obenour [this message]
2025-10-07 15:54 ` Jan Beulich
2025-10-03 22:53 ` [PATCH v3 06/22] x86/boot: Use RSTORSSP to establish SSP Andrew Cooper
2025-10-07 15:57 ` Jan Beulich
2025-10-03 22:53 ` [PATCH v3 07/22] x86/traps: Alter switch_stack_and_jump() for FRED mode Andrew Cooper
2025-10-07 15:58 ` Jan Beulich
2025-10-03 22:53 ` [PATCH v3 08/22] x86/traps: Skip Supervisor Shadow Stack tokens in " Andrew Cooper
2025-10-03 22:53 ` [PATCH v3 09/22] x86/traps: Make an IDT-specific #DB helper Andrew Cooper
2025-10-03 22:53 ` [PATCH v3 10/22] x86/traps: Make an IDT-specific #PF helper Andrew Cooper
2025-10-03 22:53 ` [PATCH v3 11/22] x86/fsgsbase: Make gskern accesses safe under FRED Andrew Cooper
2025-10-03 22:53 ` [PATCH v3 12/22] x86/traps: Introduce FRED entrypoints Andrew Cooper
2025-10-08 8:50 ` Jan Beulich
2025-10-16 14:54 ` Jan Beulich
2025-10-03 22:53 ` [PATCH v3 13/22] x86/traps: Enable FRED when requested Andrew Cooper
2025-10-08 8:54 ` Jan Beulich
2025-10-03 22:53 ` [PATCH v3 14/22] x86/pv: Deduplicate is_canonical_address() in do_set_segment_base() Andrew Cooper
2025-10-03 22:53 ` [PATCH v3 15/22] x86/entry: Alter how IRET faults are recognised Andrew Cooper
2025-10-03 22:53 ` [PATCH v3 16/22] x86/entry: Drop the pre exception table infrastructure Andrew Cooper
2025-10-03 22:53 ` [PATCH v3 17/22] x86/entry: Rework the comment about SYSCALL and DF Andrew Cooper
2025-10-03 22:53 ` [PATCH v3 18/22] x86/pv: Adjust GS handling for FRED mode Andrew Cooper
2025-10-03 22:53 ` [PATCH v3 19/22] x86/pv: Guest exception handling in " Andrew Cooper
2025-10-08 12:28 ` Jan Beulich
2025-10-03 22:53 ` [PATCH v3 20/22] x86/pv: ERETU error handling Andrew Cooper
2025-10-08 12:36 ` Jan Beulich
2025-10-03 22:53 ` [PATCH v3 21/22] x86/pv: System call handling in FRED mode Andrew Cooper
2025-10-08 13:45 ` Jan Beulich
2025-10-03 22:53 ` [PATCH v3 22/22] x86: Clamp reserved bits in eflags more aggressively Andrew Cooper
2025-10-08 13:50 ` Jan Beulich
2025-10-17 13:24 ` [PATCH v3 for-4.21 00/22] x86: FRED support Oleksii Kurochko
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