From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pg1-f170.google.com (mail-pg1-f170.google.com [209.85.215.170]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0C3FD5390 for ; Fri, 22 Dec 2023 05:42:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=rivosinc.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=rivosinc.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=rivosinc-com.20230601.gappssmtp.com header.i=@rivosinc-com.20230601.gappssmtp.com header.b="uSq/xtFj" Received: by mail-pg1-f170.google.com with SMTP id 41be03b00d2f7-5cd86e3a9afso1050191a12.1 for ; Thu, 21 Dec 2023 21:42:09 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rivosinc-com.20230601.gappssmtp.com; s=20230601; t=1703223729; x=1703828529; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=tshARWagRRHxlEAjYIN29OCOP9SHjMXaawfRGNvVCMk=; b=uSq/xtFjp1MZW/GQolvTeipl2Zd/m1GFoUGqs2XglaT8rUx+ljR8e33CVwCGCHzEx4 z8kYMlfZwUl+VhC85gz+Ku4jPEtsdrody8Qlhe9TJSBgjBzjytl1VSDbWSLoPFnuNLk8 EjjxLHXsdYeNvhPcWZsD/73scShRP/ykW/svFoGreaYjFFUmljHekpTJrUIV3rkel19N osTruUbqCQGRL6mApXJ5s/Q/oBrtyWQ+Jo4pcWZhbIspy9TKnYzzfYBT+1tMVP03vtrL /7HmVFDxTvyQTSLEg3NJwrEauhc6lDiWRsK4rBVFi8Oz25v8UZ4WRb/ssyyZDCyfg8vp NEaA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1703223729; x=1703828529; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=tshARWagRRHxlEAjYIN29OCOP9SHjMXaawfRGNvVCMk=; b=a1ss2Rlzy5NHr6MWhoHqj94KXgW/fB+j9jRywbLFPx/uKivUTJoPXC+pDokOHYF0nP k9SqdihcL0sonvn7XJrcz375ygTgVdZ1hVhJKWrfbHenS/pVpvBPaYdGKxlQzXaTSFzn IN4CzbrCZ1SCieO6yT2zN9P6Diq3TpYPiGokG5qeahiygzmlaar5Mejx9Oyu+qApDSJE /n17mh2zrZVSKvKSWrFNy0uYxczGxrmu/bvm+s6OuBb80uJWbcomZ5F0pCsQ6ySAanM6 OY84PndE7ZYipx2+RsO0Ob/p7uyaJJ+ivuLYjLyNN3c/5E36kZWy/cpQQZwcznN5FryR ej4A== X-Gm-Message-State: AOJu0YzOkACx8s2e3fPX0YxKbFxeJcKhFcBMm9QBRBnLURP1z6q2MuoT 5gA5Kk6H+W/bkw+HSC9vv5AsE/YahBeszA== X-Google-Smtp-Source: AGHT+IFPYN93FpZrSP6JEuX0E8+Rz/2HUmp3SPiiY3k73uCyVJqHwo4hbyYd5MYmWGrJPBD7tMIC/A== X-Received: by 2002:a05:6a20:8404:b0:194:7c07:5f55 with SMTP id c4-20020a056a20840400b001947c075f55mr958883pzd.54.1703223729146; Thu, 21 Dec 2023 21:42:09 -0800 (PST) Received: from ghost ([2601:647:5700:6860:f06:7450:7dd4:fc1d]) by smtp.gmail.com with ESMTPSA id j26-20020aa78d1a000000b006d974fe1b0esm2127879pfe.7.2023.12.21.21.42.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 Dec 2023 21:42:08 -0800 (PST) Date: Thu, 21 Dec 2023 21:42:05 -0800 From: Charlie Jenkins To: Leonardo Bras Cc: guoren@kernel.org, linux-kernel@vger.kernel.org, paul.walmsley@sifive.com, palmer@dabbelt.com, alexghiti@rivosinc.com, xiao.w.wang@intel.com, david@redhat.com, panqinglin2020@iscas.ac.cn, rick.p.edgecombe@intel.com, willy@infradead.org, bjorn@rivosinc.com, conor.dooley@microchip.com, cleger@rivosinc.com, linux-riscv@lists.infradead.org, Guo Ren , stable@vger.kernel.org Subject: Re: [PATCH V2 2/4] riscv: mm: Fixup compat arch_get_mmap_end Message-ID: References: <20231221154702.2267684-1-guoren@kernel.org> <20231221154702.2267684-3-guoren@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, Dec 22, 2023 at 01:23:29AM -0300, Leonardo Bras wrote: > On Thu, Dec 21, 2023 at 08:04:43PM -0800, Charlie Jenkins wrote: > > On Fri, Dec 22, 2023 at 12:34:56AM -0300, Leonardo Bras wrote: > > > On Thu, Dec 21, 2023 at 10:46:59AM -0500, guoren@kernel.org wrote: > > > > From: Guo Ren > > > > > > > > When the task is in COMPAT mode, the arch_get_mmap_end should be 2GB, > > > > not TASK_SIZE_64. The TASK_SIZE has contained is_compat_mode() > > > > detection, so change the definition of STACK_TOP_MAX to TASK_SIZE > > > > directly. > > > > > > ok > > > > > > > > > > > Cc: stable@vger.kernel.org > > > > Fixes: add2cc6b6515 ("RISC-V: mm: Restrict address space for sv39,sv48,sv57") > > > > Signed-off-by: Guo Ren > > > > Signed-off-by: Guo Ren > > > > --- > > > > arch/riscv/include/asm/processor.h | 6 ++---- > > > > 1 file changed, 2 insertions(+), 4 deletions(-) > > > > > > > > diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h > > > > index f19f861cda54..1f538fc4448d 100644 > > > > --- a/arch/riscv/include/asm/processor.h > > > > +++ b/arch/riscv/include/asm/processor.h > > > > @@ -16,15 +16,13 @@ > > > > > > > > #ifdef CONFIG_64BIT > > > > #define DEFAULT_MAP_WINDOW (UL(1) << (MMAP_VA_BITS - 1)) > > > > -#define STACK_TOP_MAX TASK_SIZE_64 > > > > +#define STACK_TOP_MAX TASK_SIZE > > > > > > It means STACK_TOP_MAX will be in 64BIT: > > > - TASK_SIZE_32 if compat_mode=y > > > - TASK_SIZE_64 if compat_mode=n > > > > > > Makes sense for me. > > > > > > > > > > > #define arch_get_mmap_end(addr, len, flags) \ > > > > ({ \ > > > > unsigned long mmap_end; \ > > > > typeof(addr) _addr = (addr); \ > > > > - if ((_addr) == 0 || (IS_ENABLED(CONFIG_COMPAT) && is_compat_task())) \ > > > > - mmap_end = STACK_TOP_MAX; \ > > > > - else if ((_addr) >= VA_USER_SV57) \ > > > > + if ((_addr) == 0 || (_addr) >= VA_USER_SV57) \ > > > > mmap_end = STACK_TOP_MAX; \ > > > > else if ((((_addr) >= VA_USER_SV48)) && (VA_BITS >= VA_BITS_SV48)) \ > > > > mmap_end = VA_USER_SV48; \ > > > > > > > > > I don't think I got this change, or how it's connected to the commit msg. > > > > > > Before: > > > - addr == 0, or addr > 2^57, or compat: mmap_end = STACK_TOP_MAX > > > - 2^48 < addr < 2^57: mmap_end = 2^48 > > > - 0 < addr < 2^48 : mmap_end = 2^39 > > > > > > Now: > > > - addr == 0, or addr > 2^57: mmap_end = STACK_TOP_MAX > > > - 2^48 < addr < 2^57: mmap_end = 2^48 > > > - 0 < addr < 2^48 : mmap_end = 2^39 > > > > > > IIUC compat mode addr will be < 2^32, so will always have mmap_end = 2^39 > > > if addr != 0. Is that desireable? > > > (if not, above change is unneeded) > > > > I agree, this change does not make sense for compat mode. Compat mode > > should never return an address that is greater than 2^32, but this > > change allows that. > > > > > > > > Also, unrelated to the change: > > > - 2^48 < addr < 2^57: mmap_end = 2^48 > > > Is the above correct? > > > It looks like it should be 2^57 instead, and a new if clause for > > > 2^32 < addr < 2^48 should have mmap_end = 2^48. > > > > That is not the case. I documented this behavior and reasoning in > > Documentation/arch/riscv/vm-layout.rst in the "Userspace VAs" section. > > > > I can reiterate here though. The hint address to mmap (defined here as > > "addr") is the maximum userspace address that mmap should provide. What > > you are describing is a minimum. The purpose of this change was to allow > > applications that are not compatible with a larger virtual address (such > > as applications like Java that use the upper bits of the VA to store > > data) to have a consistent way of specifying how many bits they would > > like to be left free in the VA. This requires to take the next lowest > > address space to guaruntee that all of the most-significant bits left > > clear in hint address do not end up populated in the virtual address > > returned by mmap. > > > > - Charlie > > Hello Charlie, thank you for helping me understand! > > Ok, that does make sense now! The addr value hints "don't allocate > addr" > and thus: > > - 0 < addr < 2^48 : mmap_end = 2^39 > - 2^48 < addr < 2^57: mmap_end = 2^48 > > Ok, but then > - addr > 2^57: mmap_end = 2^57 > right? > > I mean, probably STACK_TOP_MAX in non-compat mode means 2^57 already, but > having it explicitly like: > > else if ((_addr) >= VA_USER_SV57) \ > mmap_end = VA_USER_SV57; \ > > would not be better for a future full 64-bit addressing? > (since it's already on a different if clause) I agree, that does make more sense. > > I could add comment on top of the macro with a short version on your addr > hint description above. Would that be ok? Sure :) - Charlie > > Thanks! > Leo > > > > > > > > > > > > > Do I get it wrong? > > > > > > (I will send an RFC 'fixing' the code the way I am whinking it should look > > > like) > > > > > > Thanks, > > > Leo > > > > > > > > > > > > > > > > > > > -- > > > > 2.40.1 > > > > > > > > > >