From: Catalin Marinas <catalin.marinas@arm.com>
To: Will Deacon <will@kernel.org>
Cc: "Liao, Chang" <liaochang1@huawei.com>,
Oleg Nesterov <oleg@redhat.com>,
mhiramat@kernel.org, peterz@infradead.org, mark.rutland@arm.com,
linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] arm64: uprobes: Optimize cache flushes for xol slot
Date: Mon, 23 Sep 2024 17:03:57 +0100 [thread overview]
Message-ID: <ZvGRbeAtpAkZVhLt@arm.com> (raw)
In-Reply-To: <20240923071856.GA31866@willie-the-truck>
On Mon, Sep 23, 2024 at 08:18:57AM +0100, Will Deacon wrote:
> On Mon, Sep 23, 2024 at 09:57:14AM +0800, Liao, Chang wrote:
> > Unfortunately, the comparison assumes the D-cache and I-cache are already
> > in sync for the slot being copied. But this assumption is flawed if we start
> > with a page with some random bits and D-cache has not been sychronized with
> > I-cache. So, besides __GFP_ZERO, should we have a additional cache flush
> > after page allocation?
>
> No, I think Oleg's right. The initial cache maintenance will happen when the
> executable pte is installed.
For some reason I had kprobes in mind, did not realise that this page
ends up in user-space. So yes, we have cache maintenance when the pte is
set to point to this page. Subsequent changes will need cache
maintenance.
> However, we should use __GFP_ZERO anyway because I don't think it's a
> good idea to map an uninitialised page into userspace.
Oh, that's not good.
--
Catalin
next prev parent reply other threads:[~2024-09-23 16:04 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-09-19 12:17 [PATCH] arm64: uprobes: Optimize cache flushes for xol slot Liao Chang
2024-09-19 14:18 ` Oleg Nesterov
2024-09-20 8:58 ` Liao, Chang
2024-09-20 11:03 ` Oleg Nesterov
2024-09-20 15:32 ` Catalin Marinas
2024-09-20 17:32 ` Oleg Nesterov
2024-09-22 14:09 ` Will Deacon
2024-09-22 14:39 ` Oleg Nesterov
2024-09-23 11:16 ` Liao, Chang
2024-09-23 1:57 ` Liao, Chang
2024-09-23 7:18 ` Will Deacon
2024-09-23 10:52 ` Oleg Nesterov
2024-09-26 12:06 ` Liao, Chang
2024-09-26 16:08 ` Oleg Nesterov
2024-09-23 11:16 ` Liao, Chang
2024-09-23 16:03 ` Catalin Marinas [this message]
2024-11-06 9:55 ` Liao, Chang
2024-11-07 18:35 ` Catalin Marinas
2024-11-08 16:49 ` Catalin Marinas
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