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From: Bin Meng <bmeng.cn@gmail.com>
To: Richard Henderson <richard.henderson@linaro.org>
Cc: QEMU riscv <qemu-riscv@nongnu.org>,
	Sagar Karandikar <sagark@eecs.berkeley.edu>,
	Bastian Koppelmann <kbastian@mail.uni-paderborn.de>,
	Palmer Dabbelt <palmer@sifive.com>,
	QEMU devel <qemu-devel@nongnu.org>,
	Alistair Francis <Alistair.Francis@wdc.com>
Subject: Re: [Qemu-devel] [PATCH] riscv: rv32: Root page table address can be larger than 32-bit
Date: Thu, 1 Aug 2019 09:53:03 +0800
Message-ID: <CAEUhbmVXC6GeHYFST514cLRJHQOo5ki=ZPG=OsLzV2YA0ChQgA@mail.gmail.com> (raw)
In-Reply-To: <581a0284-c658-265f-1b0f-6f4be5406cee@linaro.org>

Hi Richard,

On Thu, Aug 1, 2019 at 1:35 AM Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> On 7/31/19 5:45 AM, Bin Meng wrote:
> > -    target_ulong base;
> > +    hwaddr base;
> ...
> > -        target_ulong pte_addr = base + idx * ptesize;
> > +        hwaddr pte_addr = base + idx * ptesize;
>
> I believe that you either need
>
>     base + (hwaddr)idx * ptesize
>
> or change the type of idx to hwaddr above.
>
> Otherwise the multiply overflows before it gets promoted with the add.
>

I am not sure how (idx * ptesize) could overflow. It represents the
offset by a page table which is [0, 4096).

Regards,
Bin


  reply index

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-31 12:45 Bin Meng
2019-07-31 17:35 ` Richard Henderson
2019-08-01  1:53   ` Bin Meng [this message]
2019-08-01 14:16     ` Richard Henderson
2019-08-01 14:57       ` Bin Meng
2019-08-07 20:55         ` Palmer Dabbelt
2019-08-08  1:49           ` Bin Meng
2019-08-08  2:49 ` [Qemu-devel] [PATCH v2] " Bin Meng
2019-08-10  1:49   ` Alistair Francis
2019-08-14  9:46     ` Bin Meng
2019-08-19  6:00       ` Bin Meng
2019-08-27 23:37         ` Palmer Dabbelt

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