From: Nick Kossifidis <mick@ics.forth.gr>
To: Palmer Dabbelt <palmer@rivosinc.com>, jrtc27@jrtc27.com
Cc: charlie@rivosinc.com, alexghiti@rivosinc.com,
Atish Patra <atishp@rivosinc.com>,
Conor Dooley <conor@kernel.org>,
Paul Walmsley <paul.walmsley@sifive.com>,
aou@eecs.berkeley.edu, Bjorn Topel <bjorn@rivosinc.com>,
anup@brainfault.org, Evan Green <evan@rivosinc.com>,
linux-riscv@lists.infradead.org, konstantin@linuxfoundation.org,
linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org,
linux-mm@kvack.org
Subject: Re: [PATCH 1/2] RISC-V: mm: Restrict address space for sv39,sv48,sv57
Date: Wed, 28 Jun 2023 10:44:26 +0300 [thread overview]
Message-ID: <6dc3a208-e180-18b4-c87e-50735edd595b@ics.forth.gr> (raw)
In-Reply-To: <mhng-7914c1d2-d671-4cc4-ba90-f85acb7c8b50@palmer-ri-x1c9>
On 6/28/23 02:36, Palmer Dabbelt wrote:
> On Tue, 27 Jun 2023 15:32:36 PDT (-0700), jrtc27@jrtc27.com wrote:
>> On 27 Jun 2023, at 23:21, Charlie Jenkins <charlie@rivosinc.com> wrote:
>>>
>>> Make sv39 the default address space for mmap as some applications
>>> currently depend on this assumption.
>>
>> They are just plain wrong too. Sv48 was in even Priv v1.10 (the first
>> spec where satp was named as such and contained the mode, rather than
>> requiring M-mode’s help in configuring virtual memory), predating the
>> ratified v1.11 spec. A 39-bit address space is pathetic and has
>> implications for ASLR.
>>
>> I strongly suggest applications be forced to support at least Sv48,
>> which is totally reasonable given the address space sizes used by other
>> architectures. Sv57 is more disruptive to some runtimes, though ideally
>> even that would be free for the kernel to use rather than committing to
>> not using it for the default uABI.
>
> Go and OpenJDK both broke when we expanded the VA width. I don't like
> it either, but if the change breaks userspace then it's a regression and
> we have to live with the bug.
>
Have we debugged this ? do we at least know why they break ? Just
disabling Sv48/57 by default for everyone because some userspace apps
break doesn't seem the correct approach, it seems more like a bug in
userspace IMHO.
next prev parent reply other threads:[~2023-06-28 7:44 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-27 22:21 [PATCH 0/2] Make SV39 the default address space Charlie Jenkins
2023-06-27 22:21 ` [PATCH 1/2] RISC-V: mm: Restrict address space for sv39,sv48,sv57 Charlie Jenkins
2023-06-27 22:32 ` Jessica Clarke
2023-06-27 23:36 ` Palmer Dabbelt
2023-06-28 7:44 ` Nick Kossifidis [this message]
2023-06-27 23:38 ` Charlie Jenkins
2023-06-28 12:34 ` Anup Patel
2023-06-29 1:38 ` Charlie Jenkins
2023-06-27 22:21 ` [PATCH 2/2] RISC-V: mm: Update documentation and include test Charlie Jenkins
2023-06-28 10:18 ` Muhammad Usama Anjum
-- strict thread matches above, loose matches on Subject: below --
2023-06-26 18:36 [PATCH 0/2] Restrict address space for sv39,sv48,sv57 Charlie Jenkins
2023-06-26 18:36 ` [PATCH 1/2] RISC-V: mm: " Charlie Jenkins
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