From: Segher Boessenkool <segher@kernel.crashing.org>
To: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: linuxppc-dev@ozlabs.org
Subject: Re: [PATCH v2 5/9] powerpc/microwatt: Use standard 16550 UART for console
Date: Thu, 12 Aug 2021 11:09:44 -0500 [thread overview]
Message-ID: <20210812160944.GU1583@gate.crashing.org> (raw)
In-Reply-To: <ec000575-7f7a-57b7-50d2-9444e17f2a7e@csgroup.eu>
On Thu, Aug 12, 2021 at 03:14:44PM +0200, Christophe Leroy wrote:
> Le 18/06/2021 à 05:46, Paul Mackerras a écrit :
> >+static u8 udbg_uart_in_isa300_rm(unsigned int reg)
> >+{
> >+ uint64_t msr = mfmsr();
> >+ uint8_t c;
> >+
> >+ mtmsr(msr & ~(MSR_EE|MSR_DR));
> >+ isync();
> >+ eieio();
> >+ c = __raw_rm_readb(UDBG_UART_MW_ADDR + (reg << 2));
> >+ mtmsr(msr);
> >+ isync();
> >+ return c;
> >+}
>
> How do you make sure that GCC won't emit any access to the stack between
> the two mtmsr() ?
The mtmsr are asm with a memory clobber so nothing will be moved between
these, and it is very unlikely anything will sprout up here out of
nothing. But yes, this whole thing should be written as real asm (or as
one huge inline asm, but ugh).
Segher
next prev parent reply other threads:[~2021-08-12 16:11 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-18 3:42 [PATCH v2 0/9] powerpc: Add support for Microwatt soft-core Paul Mackerras
2021-06-18 3:43 ` [PATCH v2 1/9] powerpc: Add Microwatt platform Paul Mackerras
2021-06-19 3:03 ` Nicholas Piggin
2021-06-18 3:44 ` [PATCH v2 2/9] powerpc: Add Microwatt device tree Paul Mackerras
2021-06-19 14:26 ` Segher Boessenkool
2021-06-20 12:08 ` Paul Mackerras
2021-06-21 13:54 ` Segher Boessenkool
2021-06-18 3:45 ` [PATCH v2 3/9] powerpc/microwatt: Populate platform bus from device-tree Paul Mackerras
2021-06-18 3:45 ` [PATCH v2 4/9] powerpc/xics: Add a native ICS backend for microwatt Paul Mackerras
2021-06-18 3:46 ` [PATCH v2 5/9] powerpc/microwatt: Use standard 16550 UART for console Paul Mackerras
2021-06-18 7:40 ` Nicholas Piggin
2021-06-18 12:12 ` Paul Mackerras
2021-06-19 2:58 ` Nicholas Piggin
2021-08-12 13:14 ` Christophe Leroy
2021-08-12 16:09 ` Segher Boessenkool [this message]
2021-06-18 3:47 ` [PATCH v2 6/9] powerpc/microwatt: Add support for hardware random number generator Paul Mackerras
2021-06-19 3:08 ` Nicholas Piggin
2021-06-19 14:36 ` Segher Boessenkool
2021-06-20 8:19 ` Nicholas Piggin
2021-06-18 3:48 ` [PATCH v2 7/9] powerpc/microwatt: Add microwatt_defconfig Paul Mackerras
2021-06-18 3:49 ` [PATCH v2 8/9] powerpc/boot: Fixup device-tree on little endian Paul Mackerras
2021-06-19 3:14 ` Nicholas Piggin
2021-06-18 3:49 ` [PATCH v2 9/9] powerpc/boot: Add a boot wrapper for Microwatt Paul Mackerras
2021-06-19 3:16 ` Nicholas Piggin
2021-06-19 14:45 ` [PATCH v2 0/9] powerpc: Add support for Microwatt soft-core Segher Boessenkool
2021-06-24 14:03 ` Michael Ellerman
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