linux-kernel - RE: [PATCH 3/4] RISC-V: Flush I$ when making a dirty page executable

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Message-ID: <9acaf467a587413a9aa1529ab8cc904e@AcuMS.aculab.com>
Date:   Tue, 21 Nov 2017 16:57:07 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Palmer Dabbelt' <palmer@...ive.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "patches@...ups.riscv.org" <patches@...ups.riscv.org>,
        Andrew Waterman <andrew@...ive.com>
Subject: RE: [PATCH 3/4] RISC-V: Flush I$ when making a dirty page executable

From: Palmer Dabbelt
> Sent: 20 November 2017 18:58
> 
> The RISC-V ISA allows for instruction caches that are not coherent WRT
> stores, even on a single hart.  As a result, we need to explicitly flush
> the instruction cache whenever marking a dirty page as executable in
> order to preserve the correct system behavior.

Isn't the I-flush only needed if there has been an unmap since the
previous I-flush?
Since code is rarely unmapped (exec and driver unload come to mind)
the I-flush won't be needed very often.

	David