From: Peter Zijlstra <peterz@infradead.org>
To: Yury Norov <ynorov@nvidia.com>
Cc: "Thomas Gleixner" <tglx@kernel.org>,
"Ingo Molnar" <mingo@redhat.com>,
"Borislav Petkov" <bp@alien8.de>,
"Dave Hansen" <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
"Andy Lutomirski" <luto@kernel.org>,
"Jonathan Cameron" <jic23@kernel.org>,
"David Lechner" <dlechner@baylibre.com>,
"Nuno Sá" <nuno.sa@analog.com>,
"Andy Shevchenko" <andy@kernel.org>,
"Ping-Ke Shih" <pkshih@realtek.com>,
"Richard Cochran" <richardcochran@gmail.com>,
"Andrew Lunn" <andrew+netdev@lunn.ch>,
"David S. Miller" <davem@davemloft.net>,
"Eric Dumazet" <edumazet@google.com>,
"Jakub Kicinski" <kuba@kernel.org>,
"Paolo Abeni" <pabeni@redhat.com>,
"Alexandre Belloni" <alexandre.belloni@bootlin.com>,
"Yury Norov" <yury.norov@gmail.com>,
"Rasmus Villemoes" <linux@rasmusvillemoes.dk>,
"Hans de Goede" <hansg@kernel.org>,
"Linus Walleij" <linusw@kernel.org>,
"Sakari Ailus" <sakari.ailus@linux.intel.com>,
"Salah Triki" <salah.triki@gmail.com>,
"Achim Gratz" <Achim.Gratz@stromeko.de>,
"Ben Collins" <bcollins@watter.com>,
linux-kernel@vger.kernel.org, linux-iio@vger.kernel.org,
linux-wireless@vger.kernel.org, netdev@vger.kernel.org,
linux-rtc@vger.kernel.org
Subject: Re: [PATCH 2/9] x86/extable: switch to using FIELD_GET_SIGNED()
Date: Mon, 20 Apr 2026 13:24:28 +0200 [thread overview]
Message-ID: <20260420112428.GF3102624@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20260417173621.368914-3-ynorov@nvidia.com>
On Fri, Apr 17, 2026 at 01:36:13PM -0400, Yury Norov wrote:
> The EX_DATA register is laid out such that EX_DATA_IMM occupied MSB.
> It's done to make sure that FIELD_GET() will sign-extend the IMM
> field during extraction.
>
> To enforce that, all EX_DATA masks are made signed integers. This
> works, but relies on the particular implementation of FIELD_GET(),
> i.e. masking then shifting, not vice versa; and the particular
> placement of the fields in the register.
I don't think the order of the mask and shift matters in this case. If
we were to first shift down and then mask, it would still work (after
all, the mask would also need to be shifted and would also get sign
extended, effectively ending up as -1).
But yes, this very much depends on the signed field being the topmost
field and including the MSB.
next prev parent reply other threads:[~2026-04-20 11:24 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-17 17:36 [PATCH 0/9] bitfield: add FIELD_GET_SIGNED() Yury Norov
2026-04-17 17:36 ` [PATCH 1/9] " Yury Norov
2026-04-17 18:12 ` Andy Shevchenko
2026-04-17 19:43 ` David Laight
2026-04-17 21:09 ` Yury Norov
2026-04-20 8:43 ` Johannes Berg
2026-04-20 11:19 ` Peter Zijlstra
2026-04-20 17:54 ` Yury Norov
2026-04-21 9:27 ` David Laight
2026-04-17 17:36 ` [PATCH 2/9] x86/extable: switch to using FIELD_GET_SIGNED() Yury Norov
2026-04-20 11:24 ` Peter Zijlstra [this message]
2026-04-20 17:18 ` Yury Norov
2026-04-20 22:00 ` David Laight
2026-04-17 17:36 ` [PATCH 3/9] iio: intel_dc_ti_adc: " Yury Norov
2026-04-19 13:18 ` Jonathan Cameron
2026-04-17 17:36 ` [PATCH 4/9] iio: magnetometer: yas530: " Yury Norov
2026-04-19 13:20 ` Jonathan Cameron
2026-04-19 20:11 ` Linus Walleij
2026-04-17 17:36 ` [PATCH 5/9] iio: pressure: bmp280: " Yury Norov
2026-04-19 13:21 ` Jonathan Cameron
2026-04-17 17:36 ` [PATCH 6/9] iio: mcp9600: " Yury Norov
2026-04-19 13:21 ` Jonathan Cameron
2026-04-17 17:36 ` [PATCH 7/9] wifi: rtw89: " Yury Norov
2026-04-20 7:49 ` Ping-Ke Shih
2026-04-20 17:59 ` Yury Norov
2026-04-17 17:36 ` [PATCH 8/9] rtc: rv3032: " Yury Norov
2026-04-17 17:36 ` [PATCH 9/9] ptp: " Yury Norov
2026-04-17 18:23 ` [PATCH 0/9] bitfield: add FIELD_GET_SIGNED() Andy Shevchenko
2026-04-17 19:21 ` Yury Norov
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