From: Robin Murphy <robin.murphy@arm.com>
To: Mark Rutland <mark.rutland@arm.com>,
Shanker Donthineni <shankerd@codeaurora.org>
Cc: Philip Elcan <pelcan@codeaurora.org>,
Marc Zyngier <marc.zyngier@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
kvmarm <kvmarm@lists.cs.columbia.edu>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v4] arm64: Add support for new control bits CTR_EL0.DIC and CTR_EL0.IDC
Date: Thu, 22 Feb 2018 16:28:03 +0000 [thread overview]
Message-ID: <32c8cfd3-2883-177b-7736-1bb6ab679df4@arm.com> (raw)
In-Reply-To: <20180222152244.zozx2tlptgnnfu6b@lakrids.cambridge.arm.com>
[Apologies to keep elbowing in, and if I'm being thick here...]
On 22/02/18 15:22, Mark Rutland wrote:
> On Thu, Feb 22, 2018 at 08:51:30AM -0600, Shanker Donthineni wrote:
>> +#define CTR_B31_SHIFT 31
>
> Since this is just a RES1 bit, I think we don't need a mnemonic for it,
> but I'll defer to Will and Catalin on that.
>
>> ENTRY(invalidate_icache_range)
>> +#ifdef CONFIG_ARM64_SKIP_CACHE_POU
>> +alternative_if ARM64_HAS_CACHE_DIC
>> + mov x0, xzr
>> + dsb ishst
>> + isb
>> + ret
>> +alternative_else_nop_endif
>> +#endif
>
> As commented on v3, I don't believe you need the DSB here. If prior
> stores haven't been completed at this point, the existing implementation
> would not work correctly here.
True in terms of ordering between stores prior to entry and the IC IVAU
itself, but what about the DSH ISH currently issued *after* the IC IVAU
before returning? Is provably impossible that existing callers might be
relying on that ordering *anything*, or would we risk losing something
subtle by effectively removing it?
Robin.
next prev parent reply other threads:[~2018-02-22 16:28 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-22 14:51 [PATCH v4] arm64: Add support for new control bits CTR_EL0.DIC and CTR_EL0.IDC Shanker Donthineni
2018-02-22 15:22 ` Mark Rutland
2018-02-22 16:28 ` Robin Murphy [this message]
2018-02-22 16:33 ` Mark Rutland
2018-02-22 16:53 ` Robin Murphy
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