From patchwork Sat Jan 20 21:49:58 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yangyu Chen X-Patchwork-Id: 13524466 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 83790C47DAF for ; Sat, 20 Jan 2024 21:50:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Date:Subject:Cc:To:From:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=8UmvJsABgKejrop8oVezGydWi2baax7Fur4d0uMADk0=; b=C4KBu641zCCtk5 sk8m9sdxogCOO/m/TJYm4LnpYOpDg8V0X+es/HWijVp/i6ceY8PQYJweveOy9vJTfCvOYcdQQswng ZdcnB4+GvnB54CIBfoWJ/+BGkqfhgYKG8ziYL5rtMtRj2b8/YQYUsrqhTngg80hHFmyIz7/CJULMh CtSCxKcuvwXxkGVX8M9nANiY2k6Nua6MWElzaeVFKFQpPo4YITSRCu/ZI6r0cy8BARwh/M/2N4H9i w+7RhB8P94lMSdC0l7IyX9oEDrAFftycL/FVuI4sKw2qYegi6m09grd1KjXFVxG/dUGWs4v+lI385 D37OJDUEn+wBy1tXUr2Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1rRJEM-008TNx-00; Sat, 20 Jan 2024 21:50:22 +0000 Received: from out203-205-221-233.mail.qq.com ([203.205.221.233]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1rRJEG-008TMG-0l for linux-riscv@lists.infradead.org; Sat, 20 Jan 2024 21:50:20 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=qq.com; s=s201512; t=1705787407; bh=4nmX4hKeh/0WuigJrd8ANC0wflYIcPXPQU4r0VNEKp8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=BCTJUEnRp+uC0d0dRxHQsm/zVTkvWgVkAiSDO/Np0gxMBiylPltmYRRlaUxuRE5dT JNImCpHL9Z4E39CTM/nzV/g84s+7awuJxhKqNJLPRWtD/xn8+67ZyD+5zra9Iqkfk5 J9hS+sWGY04ORFsXjGfpC4+g8/l88pMguMUorMpg= Received: from cyy-pc.lan ([240e:379:2240:ed00:c92f:86c3:e615:ca18]) by newxmesmtplogicsvrszc5-0.qq.com (NewEsmtp) with SMTP id C832D4DD; Sun, 21 Jan 2024 05:50:03 +0800 X-QQ-mid: xmsmtpt1705787403tnr6elyfm Message-ID: X-QQ-XMAILINFO: OPDQNGCUQ3qLjMTDsrPToOp8oyErPnL2SII8vV9kBmlMV/zje0JtvQMeaBQSLy B2QJFDDnOzluHBIoK3YrDakeYq1fWVYfn74YrxBVVRd8tl+v2/yLAywxvW+k44gaNKX0N25jyf+t WrPkrf8crNxwu7VPCeY43GXT7J1T8nntnPO/6OtzZ27FP6ibc1/EISwFYOuKUF1Ztq1j8CZDEY62 nHhBvzrqDea94mJGzZZ6dTCKXpg8YE6ggXAR1ycnSX1nUuz441T3r9p6eE+dbnEIctVBEgOkYTqY NZFVL4uwWf6RoC5X3ykYjE9NXqs1aCyf2K7tovE8dlIVLrUAiZTuoIIq04uKiGxF6pKhhtUabb+W IOscWMkKMcFVpW+LUTdBGEoQ9MgiMAzKEdbRJ01mK5piJuHFw2Rw+PnwunWv3tFZCGKP5yyn5Px9 GtU7ks9X0jco8acac37axmjiySgqH5Sw30F6SAbbCZCK8JwyZQ47x+zrWa35EnSl8FcQDZ5hehbw qPYQEqQUlgI1Zp5/DNNPJc39PKDeuFD9GOL1WySOS5siYySwsyr04wvTPnPu+iHD37tiMhSmQ2ny mYsBKzRvjMXAFGRaQKacp39hdh8w1HpeuPmRBoY543PPeXgDQbiPxeAdQWqX+UcQ9GiqV03ul2Rx BJAqgNlKukFM0q1Cxv8PetFLS2GktGbAjpuuPTBt2dv6uJdZywgTBmm1wWGgkmFGMK2GzBwQRhb4 lUxxrf6bvMi0RNZzzWHQknlNc57BfIoYi9+KlMb6oPd4h2CUgkXcJzylpt23Uw2qiBrJXMO2U0CZ J6P0lWu2HoLu90um4XA1X+tgwXIvydZVnZzHKOEw7Gpvi1Fi09/ABN4Ub2Pa7RLTIU72Rj87xIkh bmIN8Db8FDf1vQAURV5C3ZuslG/UO1aJ8Zincg1F4sSugX+WZXDqUYtUCIj2vddR9JwJhuka6alp ygJd0xxijjWzsLCCayIR99Dfr/ijIim+Z3cuceuUmlob4bU1jZwoh5pvhl8Q2/c10Bj37a/jyDxR eCDOn+v55wx5G1hZ7R7Lo7MkdxHpg= X-QQ-XMRINFO: M/715EihBoGSf6IYSX1iLFg= From: Yangyu Chen To: linux-riscv@lists.infradead.org Cc: Charlie Jenkins , Paul Walmsley , Palmer Dabbelt , Guo Ren , Andy Chiu , Conor Dooley , Jisheng Zhang , Alexandre Ghiti , linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Yangyu Chen Subject: [PATCH v2 1/3] RISC-V: mm: do not treat hint addr on mmap as the upper bound to search Date: Sun, 21 Jan 2024 05:49:58 +0800 X-OQ-MSGID: <20240120215000.291877-1-cyy@cyyself.name> X-Mailer: git-send-email 2.43.0 In-Reply-To: References: MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240120_135016_602916_FEE6B4E1 X-CRM114-Status: GOOD ( 15.77 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org This patch reverted the meaning of the addr parameter in the mmap syscall change from the previous commit add2cc6b6515 ("RISC-V: mm: Restrict address space for sv39,sv48,sv57") from patch[1] which treats hint addr as the upper bound of the mmap return address. However, some userspace software assumes mmap will attempt to create mapping on the hint address if possible without MAP_FIXED set, thus these software will always use the fallback path as the return address is not the same as the hint, which may lead to some performance overhead. Other ISAs like x86, arm64, and powerpc also meet this issue which has userspace virtual address bits larger than 48-bit and userspace software may use the MSB beyond 48-bit to store some information. Still, these ISAs didn't change the meaning of the hint address and only limited the address space to 48-bit when the hint address did not go beyond the default map window. Thus, this patch makes the behavior of mmap syscall on RISC-V sv57 capable system align with x86, arm64, powerpc by only limiting the address space to DEFAULT_MAP_WINDOW which is defined as not larger than 47-bit. If a user program wants to use sv57 address space, it can use mmap with a hint address larger than BIT(47) as it is already documented in x86 and arm64. And this code is copied from kernel source code on powerpc. [1]. https://lore.kernel.org/r/20230809232218.849726-2-charlie@rivosinc.com Signed-off-by: Yangyu Chen --- arch/riscv/include/asm/processor.h | 38 ++++++------------------------ 1 file changed, 7 insertions(+), 31 deletions(-) diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h index a8509cc31ab2..bc604669f18e 100644 --- a/arch/riscv/include/asm/processor.h +++ b/arch/riscv/include/asm/processor.h @@ -18,37 +18,13 @@ #define DEFAULT_MAP_WINDOW (UL(1) << (MMAP_VA_BITS - 1)) #define STACK_TOP_MAX TASK_SIZE -#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) \ - mmap_end = STACK_TOP_MAX; \ - else if ((((_addr) >= VA_USER_SV48)) && (VA_BITS >= VA_BITS_SV48)) \ - mmap_end = VA_USER_SV48; \ - else \ - mmap_end = VA_USER_SV39; \ - mmap_end; \ -}) - -#define arch_get_mmap_base(addr, base) \ -({ \ - unsigned long mmap_base; \ - typeof(addr) _addr = (addr); \ - typeof(base) _base = (base); \ - unsigned long rnd_gap = DEFAULT_MAP_WINDOW - (_base); \ - if ((_addr) == 0 || (IS_ENABLED(CONFIG_COMPAT) && is_compat_task())) \ - mmap_base = (_base); \ - else if (((_addr) >= VA_USER_SV57) && (VA_BITS >= VA_BITS_SV57)) \ - mmap_base = VA_USER_SV57 - rnd_gap; \ - else if ((((_addr) >= VA_USER_SV48)) && (VA_BITS >= VA_BITS_SV48)) \ - mmap_base = VA_USER_SV48 - rnd_gap; \ - else \ - mmap_base = VA_USER_SV39 - rnd_gap; \ - mmap_base; \ -}) +#define arch_get_mmap_end(addr, len, flags) \ + (((addr) > DEFAULT_MAP_WINDOW) || \ + (((flags) & MAP_FIXED) && ((addr) + (len) > DEFAULT_MAP_WINDOW)) ? TASK_SIZE : \ + DEFAULT_MAP_WINDOW) + +#define arch_get_mmap_base(addr, base) \ + (((addr) > DEFAULT_MAP_WINDOW) ? (base) + TASK_SIZE - DEFAULT_MAP_WINDOW : (base)) #else #define DEFAULT_MAP_WINDOW TASK_SIZE From patchwork Sat Jan 20 21:49:59 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yangyu Chen X-Patchwork-Id: 13524465 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 495AFC47DAF for ; Sat, 20 Jan 2024 21:50:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Date:Subject:Cc:To:From:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=6Sc/ghpnriUjAlLpzdPaUn50cpx/4Yq4y8jGhiUNeZU=; b=li6YK4jT5Bv9VE +ynqtArsFNTN+OK6DW8VVr1uaOty2tzWmm2dtzw+t8Y0O7C38mJhptWSbM6z5Nm0m3NMo21vq7+uj J6lqAw6cmxJb3YLIYacGFkXYg8ND+JhsSDxLysc8PTQvxFxRg7rpkyK/diGuMWlliyhF5OrwyfD/e xDOE1Sxe6mVQwfHTVrapHvpQ6GrowwAuwjlYuT3iAkxP3D+r4hnOHuVJRlHdvMdU8BQXOzWlFelol TVy2sJflU9pXPMbvmdjpBf8y/jE/lAthNPjWotyoiqhV0ajLOGZA26Y9n7D87esIeF5gPkFpURBao ZmY1kXneS91y0RdINydA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1rRJEH-008TMr-0r; Sat, 20 Jan 2024 21:50:17 +0000 Received: from out203-205-221-242.mail.qq.com ([203.205.221.242]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1rRJEC-008TLr-1s for linux-riscv@lists.infradead.org; Sat, 20 Jan 2024 21:50:16 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=qq.com; s=s201512; t=1705787409; bh=SbEh5VB4GzFFImDZ98RQo/aVP6rIyZlESD+33dGh2Zg=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=NuCknl05Y9BtPtHq3TniUiL8depkg9vZKlYCkx+8ht7fkZvZLox6tld6yr4tMCcfK p2RNjRj9IEN4CFZmKeJ5S14KG4DLVdXaAaYvwDrEax6SUk1nxG4igG2PiqON5T2GOi TarUkkMa/8+8hJ/D2CuYy/uex17L5WBZDQk5IlS8= Received: from cyy-pc.lan ([240e:379:2240:ed00:c92f:86c3:e615:ca18]) by newxmesmtplogicsvrszc5-0.qq.com (NewEsmtp) with SMTP id C832D4DD; Sun, 21 Jan 2024 05:50:03 +0800 X-QQ-mid: xmsmtpt1705787406tbsozqm54 Message-ID: X-QQ-XMAILINFO: MRMtjO3A6C9XdO4Vg7r72bh7nPfnPN7h7nnFbDIZFVbwGB1EPTLF5c6L4O17kK okydMi0HSUFb3ygdby52DFLVNzPj6QYxpuKP/VYfWtXuvjyJWsNtwxSP5HGM1zjpBOgCdTLngkQM arhxCEz+4wmwvCZ6Pz8BstxjVpsrfxUnHbAKBlnwf710ssPN3bFjgFa6RlvLsTlU4KOfmtNjfbet W1qX99HU3HRJTYqpG2w71qPx0mD91MIvs47SunOsARj5c1c+j6eC29HI+tDRi42NvlWJGMcV8vFy vno5buf4nACHogJIGezz6ZDGlx+Md+mdT2P2hBlpqhBEWLtCMsS5xDLSa84Q9z7dR2hBn7GcLgDU OQgJN+cX9ihAqO5O1aNfAEtQ2R2NGpTosfTd/dSYiFwTSHQUnTpAk2csxacyg54NKtQwYl5Cv/g3 DdIZ1R2V803HtjTwvm2HQ6dkgG2Z5O7S3JWmJRoQ7j+ldZgVGvuvmbkPO7C9P5UttbIYZ6YM6b/R ufXJ17oaFOwmRkcrlQzukx3v6dJZm91qAOkAfqRZ2WH5Q6W/a1NPndCZwB9NOXsEh6dvZnC3/aLw 9RY/JTGFTLFsUvfanbMupBuTUlT9f7eHLh4gCM16c4RYb9gJHg0sxYFnsSOT9hLlIf6MvqtuHdSC zko3RiXHGhVf7HidLg9OVbjVbYZC+qn5ixDPtkI89rEG9sNSB0NbUfp6rW7IgwNHEPZi6flnV7z1 08eGSe5ow5R4aqwZnhPV9fNG0L8ESzn6mEiwxkTojUSAWqCbQFvYUHYgyNvoPZwwNr+UxAn1YftN tl47WLcn4IZn3LvtUJpA4qDQsAM3rULwsfLBYiVaPjglnNgZdgTnj7KW6nSuACUEM9d/ywH+XqeY 2bAXEeXvY9PaMVfR2ONG2i88yEh3h/cFq6HSCVY6UHhNSBz1uGQ4cPcsDlDbtUeV/GM1GjVXGG8O CzFRgV6aJwKNeVr+EctVVgKBxZ5za8xhjzLPo/ljYPJSGoQwrJQEd+nl/ShJyabAc9uCYCHE+dkD US+Bylb9/aetiTdVGmNmb0p6jQhaQ= X-QQ-XMRINFO: OWPUhxQsoeAVDbp3OJHYyFg= From: Yangyu Chen To: linux-riscv@lists.infradead.org Cc: Charlie Jenkins , Paul Walmsley , Palmer Dabbelt , Guo Ren , Andy Chiu , Conor Dooley , Jisheng Zhang , Alexandre Ghiti , linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Yangyu Chen Subject: [PATCH v2 2/3] RISC-V: mm: only test mmap without hint Date: Sun, 21 Jan 2024 05:49:59 +0800 X-OQ-MSGID: <20240120215000.291877-2-cyy@cyyself.name> X-Mailer: git-send-email 2.43.0 In-Reply-To: References: MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240120_135012_952085_73CCF135 X-CRM114-Status: UNSURE ( 7.97 ) X-CRM114-Notice: Please train this message. X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org The original test from the previous patchset[1] assumes the hint address on mmap is treated as the upper bound of the return address. As we reverted this special behavior, this test should be updated to reflect the change. [1]. https://lore.kernel.org/linux-riscv/20230809232218.849726-1-charlie@rivosinc.com/ Signed-off-by: Yangyu Chen --- .../selftests/riscv/mm/mmap_bottomup.c | 12 -------- .../testing/selftests/riscv/mm/mmap_default.c | 12 -------- tools/testing/selftests/riscv/mm/mmap_test.h | 30 ------------------- 3 files changed, 54 deletions(-) diff --git a/tools/testing/selftests/riscv/mm/mmap_bottomup.c b/tools/testing/selftests/riscv/mm/mmap_bottomup.c index 1757d19ca89b..1ba703d3f552 100644 --- a/tools/testing/selftests/riscv/mm/mmap_bottomup.c +++ b/tools/testing/selftests/riscv/mm/mmap_bottomup.c @@ -15,20 +15,8 @@ TEST(infinite_rlimit) do_mmaps(&mmap_addresses); EXPECT_NE(MAP_FAILED, mmap_addresses.no_hint); - EXPECT_NE(MAP_FAILED, mmap_addresses.on_37_addr); - EXPECT_NE(MAP_FAILED, mmap_addresses.on_38_addr); - EXPECT_NE(MAP_FAILED, mmap_addresses.on_46_addr); - EXPECT_NE(MAP_FAILED, mmap_addresses.on_47_addr); - EXPECT_NE(MAP_FAILED, mmap_addresses.on_55_addr); - EXPECT_NE(MAP_FAILED, mmap_addresses.on_56_addr); EXPECT_GT(1UL << 47, (unsigned long)mmap_addresses.no_hint); - EXPECT_GT(1UL << 38, (unsigned long)mmap_addresses.on_37_addr); - EXPECT_GT(1UL << 38, (unsigned long)mmap_addresses.on_38_addr); - EXPECT_GT(1UL << 38, (unsigned long)mmap_addresses.on_46_addr); - EXPECT_GT(1UL << 47, (unsigned long)mmap_addresses.on_47_addr); - EXPECT_GT(1UL << 47, (unsigned long)mmap_addresses.on_55_addr); - EXPECT_GT(1UL << 56, (unsigned long)mmap_addresses.on_56_addr); #endif } diff --git a/tools/testing/selftests/riscv/mm/mmap_default.c b/tools/testing/selftests/riscv/mm/mmap_default.c index c63c60b9397e..f1ac860dcf04 100644 --- a/tools/testing/selftests/riscv/mm/mmap_default.c +++ b/tools/testing/selftests/riscv/mm/mmap_default.c @@ -15,20 +15,8 @@ TEST(default_rlimit) do_mmaps(&mmap_addresses); EXPECT_NE(MAP_FAILED, mmap_addresses.no_hint); - EXPECT_NE(MAP_FAILED, mmap_addresses.on_37_addr); - EXPECT_NE(MAP_FAILED, mmap_addresses.on_38_addr); - EXPECT_NE(MAP_FAILED, mmap_addresses.on_46_addr); - EXPECT_NE(MAP_FAILED, mmap_addresses.on_47_addr); - EXPECT_NE(MAP_FAILED, mmap_addresses.on_55_addr); - EXPECT_NE(MAP_FAILED, mmap_addresses.on_56_addr); EXPECT_GT(1UL << 47, (unsigned long)mmap_addresses.no_hint); - EXPECT_GT(1UL << 38, (unsigned long)mmap_addresses.on_37_addr); - EXPECT_GT(1UL << 38, (unsigned long)mmap_addresses.on_38_addr); - EXPECT_GT(1UL << 38, (unsigned long)mmap_addresses.on_46_addr); - EXPECT_GT(1UL << 47, (unsigned long)mmap_addresses.on_47_addr); - EXPECT_GT(1UL << 47, (unsigned long)mmap_addresses.on_55_addr); - EXPECT_GT(1UL << 56, (unsigned long)mmap_addresses.on_56_addr); #endif } diff --git a/tools/testing/selftests/riscv/mm/mmap_test.h b/tools/testing/selftests/riscv/mm/mmap_test.h index 2e0db9c5be6c..d2271426288f 100644 --- a/tools/testing/selftests/riscv/mm/mmap_test.h +++ b/tools/testing/selftests/riscv/mm/mmap_test.h @@ -10,47 +10,17 @@ struct addresses { int *no_hint; - int *on_37_addr; - int *on_38_addr; - int *on_46_addr; - int *on_47_addr; - int *on_55_addr; - int *on_56_addr; }; // Only works on 64 bit #if __riscv_xlen == 64 static inline void do_mmaps(struct addresses *mmap_addresses) { - /* - * Place all of the hint addresses on the boundaries of mmap - * sv39, sv48, sv57 - * User addresses end at 1<<38, 1<<47, 1<<56 respectively - */ - void *on_37_bits = (void *)(1UL << 37); - void *on_38_bits = (void *)(1UL << 38); - void *on_46_bits = (void *)(1UL << 46); - void *on_47_bits = (void *)(1UL << 47); - void *on_55_bits = (void *)(1UL << 55); - void *on_56_bits = (void *)(1UL << 56); - int prot = PROT_READ | PROT_WRITE; int flags = MAP_PRIVATE | MAP_ANONYMOUS; mmap_addresses->no_hint = mmap(NULL, 5 * sizeof(int), prot, flags, 0, 0); - mmap_addresses->on_37_addr = - mmap(on_37_bits, 5 * sizeof(int), prot, flags, 0, 0); - mmap_addresses->on_38_addr = - mmap(on_38_bits, 5 * sizeof(int), prot, flags, 0, 0); - mmap_addresses->on_46_addr = - mmap(on_46_bits, 5 * sizeof(int), prot, flags, 0, 0); - mmap_addresses->on_47_addr = - mmap(on_47_bits, 5 * sizeof(int), prot, flags, 0, 0); - mmap_addresses->on_55_addr = - mmap(on_55_bits, 5 * sizeof(int), prot, flags, 0, 0); - mmap_addresses->on_56_addr = - mmap(on_56_bits, 5 * sizeof(int), prot, flags, 0, 0); } #endif /* __riscv_xlen == 64 */ From patchwork Sat Jan 20 21:50:00 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yangyu Chen X-Patchwork-Id: 13524467 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 692FAC47DAF for ; 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Most of the content is copied from the corresponding feature in x86_64 with some modifications to align with the current kernel's behavior on RISC-V. [1]. https://lore.kernel.org/linux-riscv/20230809232218.849726-1-charlie@rivosinc.com/ Signed-off-by: Yangyu Chen --- Documentation/arch/riscv/vm-layout.rst | 54 ++++++++++++++++---------- 1 file changed, 34 insertions(+), 20 deletions(-) diff --git a/Documentation/arch/riscv/vm-layout.rst b/Documentation/arch/riscv/vm-layout.rst index 69ff6da1dbf8..9d84362b9f91 100644 --- a/Documentation/arch/riscv/vm-layout.rst +++ b/Documentation/arch/riscv/vm-layout.rst @@ -135,23 +135,37 @@ RISC-V Linux Kernel SV57 __________________|____________|__________________|_________|____________________________________________________________ -Userspace VAs --------------------- -To maintain compatibility with software that relies on the VA space with a -maximum of 48 bits the kernel will, by default, return virtual addresses to -userspace from a 48-bit range (sv48). This default behavior is achieved by -passing 0 into the hint address parameter of mmap. On CPUs with an address space -smaller than sv48, the CPU maximum supported address space will be the default. - -Software can "opt-in" to receiving VAs from another VA space by providing -a hint address to mmap. A hint address passed to mmap will cause the largest -address space that fits entirely into the hint to be used, unless there is no -space left in the address space. If there is no space available in the requested -address space, an address in the next smallest available address space will be -returned. - -For example, in order to obtain 48-bit VA space, a hint address greater than -:code:`1 << 47` must be provided. Note that this is 47 due to sv48 userspace -ending at :code:`1 << 47` and the addresses beyond this are reserved for the -kernel. Similarly, to obtain 57-bit VA space addresses, a hint address greater -than or equal to :code:`1 << 56` must be provided. +User-space and large virtual address space +========================================== +On RISC-V, Sv57 paging enables 56-bit userspace virtual address space. +Not all user space is ready to handle wide addresses. It's known that +at least some JIT compilers use higher bits in pointers to encode their +information. It collides with valid pointers with Sv57 paging and leads +to crashes. + +To mitigate this, we are not going to allocate virtual address space +above 47-bit by default. And on kernel v6.6-v6.7, that is 38-bit by +default. + +But userspace can ask for allocation from full address space by +specifying hint address (with or without MAP_FIXED) above 47-bits, or +hint address + size above 47-bits with MAP_FIXED. + +If hint address set above 47-bit, but MAP_FIXED is not specified, we try +to look for unmapped area by specified address. If it's already +occupied, we look for unmapped area in *full* address space, rather than +from 47-bit window. + +A high hint address would only affect the allocation in question, but not +any future mmap()s. + +Specifying high hint address without MAP_FIXED on older kernel or on +machine without Sv57 paging support is safe. On kernel v6.6-v6.7, the +hint will be treated as the upper bound of the address space to search, +but this was removed in the future version of kernels. On kernel older +than v6.6 or on machine without Sv57 paging support, the kernel will +fall back to allocation from the supported address space. + +This approach helps to easily make application's memory allocator aware +about large address space without manually tracking allocated virtual +address space.