From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B03F2C43381 for ; Tue, 19 Mar 2019 18:08:25 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 8475E20685 for ; Tue, 19 Mar 2019 18:08:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="aFz08RHW" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8475E20685 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:MIME-Version:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:References: In-Reply-To:Message-Id:Date:Subject:To:From:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; bh=0RsMW1nX0vpSK7zwRuTuEtU0Z+V7LG5YvFAszhOI8Lc=; b=aFz08RHWXaEyYh2fni0AVDpbX0 p1d78SS9kPiouXhcQfVf18Br1zdmKwURuuZcTjv3ZMyu0Wjwn9y7eaBgeSKBGyBuSkz2xd8a6eH+P RK/AgVWIUz9/SD2ehmGQSOD7lcwjm99vKcY4ju3G4Xw2vZRvb2ZqH6S7HKWlAHqACwLkcI//Ak0Jd Y7LNJrBsCt2gIFbKITGIE9b205uzi9x3Pa+/uhcQltbyMwymgm3VvcN7qHhFZsK1lFtw/6TeIPil4 7KmzKeshrmxJ5gpHVW7l3ofTjZwvlCuIatly9bwDap3cAHys+FP8gukC+ooS5IZdggtWAr5i1XgaZ DKVZgNoQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1h6J9u-0003pu-5k; Tue, 19 Mar 2019 18:08:18 +0000 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70] helo=foss.arm.com) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1h6IvQ-0000yo-Nk for linux-arm-kernel@lists.infradead.org; Tue, 19 Mar 2019 17:53:22 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 8B71E1596; Tue, 19 Mar 2019 10:53:20 -0700 (PDT) Received: from e103592.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 9B1DA3F614; Tue, 19 Mar 2019 10:53:18 -0700 (PDT) From: Dave Martin To: kvmarm@lists.cs.columbia.edu Subject: [PATCH v6 07/27] arm64/sve: Check SVE virtualisability Date: Tue, 19 Mar 2019 17:51:58 +0000 Message-Id: <1553017938-710-8-git-send-email-Dave.Martin@arm.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1553017938-710-1-git-send-email-Dave.Martin@arm.com> References: <1553017938-710-1-git-send-email-Dave.Martin@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190319_105320_894516_FA83C8DF X-CRM114-Status: GOOD ( 23.66 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , Okamoto Takayuki , Christoffer Dall , Ard Biesheuvel , Marc Zyngier , Catalin Marinas , Will Deacon , Zhang Lei , Julien Grall , =?UTF-8?q?Alex=20Benn=C3=A9e?= , linux-arm-kernel@lists.infradead.org MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Due to the way the effective SVE vector length is controlled and trapped at different exception levels, certain mismatches in the sets of vector lengths supported by different physical CPUs in the system may prevent straightforward virtualisation of SVE at parity with the host. This patch analyses the extent to which SVE can be virtualised safely without interfering with migration of vcpus between physical CPUs, and rejects late secondary CPUs that would erode the situation further. It is left up to KVM to decide what to do with this information. Signed-off-by: Dave Martin Reviewed-by: Julien Thierry --- QUESTION: The final structure of this code makes it quite natural to clamp the vector length for KVM guests to the maximum value supportable across all CPUs; such a value is guaranteed to exist, but may be surprisingly small on a given hardware platform. Should we be stricter and actually refuse to support KVM at all on such hardware? This may help to force people to fix Linux (or the architecture) if/when this issue comes up. For now, I stick with pr_warn() and make do with a limited SVE vector length for guests. Changes since v5: * pr_info() about the presence of unvirtualisable vector lengths in sve_setup() upgrade to pr_warn(), for consistency with sve_verify_vq_map(). --- arch/arm64/include/asm/fpsimd.h | 1 + arch/arm64/kernel/cpufeature.c | 2 +- arch/arm64/kernel/fpsimd.c | 86 ++++++++++++++++++++++++++++++++++------- 3 files changed, 73 insertions(+), 16 deletions(-) diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h index dd1ad39..964adc9 100644 --- a/arch/arm64/include/asm/fpsimd.h +++ b/arch/arm64/include/asm/fpsimd.h @@ -87,6 +87,7 @@ extern void sve_kernel_enable(const struct arm64_cpu_capabilities *__unused); extern u64 read_zcr_features(void); extern int __ro_after_init sve_max_vl; +extern int __ro_after_init sve_max_virtualisable_vl; #ifdef CONFIG_ARM64_SVE diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index e24e94d..4b1cda5 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -1862,7 +1862,7 @@ static void verify_sve_features(void) unsigned int len = zcr & ZCR_ELx_LEN_MASK; if (len < safe_len || sve_verify_vq_map()) { - pr_crit("CPU%d: SVE: required vector length(s) missing\n", + pr_crit("CPU%d: SVE: vector length support mismatch\n", smp_processor_id()); cpu_die_early(); } diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c index f59ea67..b219796a 100644 --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -18,6 +18,7 @@ */ #include +#include #include #include #include @@ -48,6 +49,7 @@ #include #include #include +#include #define FPEXC_IOF (1 << 0) #define FPEXC_DZF (1 << 1) @@ -130,14 +132,18 @@ static int sve_default_vl = -1; /* Maximum supported vector length across all CPUs (initially poisoned) */ int __ro_after_init sve_max_vl = SVE_VL_MIN; +int __ro_after_init sve_max_virtualisable_vl = SVE_VL_MIN; /* Set of available vector lengths, as vq_to_bit(vq): */ static __ro_after_init DECLARE_BITMAP(sve_vq_map, SVE_VQ_MAX); +/* Set of vector lengths present on at least one cpu: */ +static __ro_after_init DECLARE_BITMAP(sve_vq_partial_map, SVE_VQ_MAX); static void __percpu *efi_sve_state; #else /* ! CONFIG_ARM64_SVE */ /* Dummy declaration for code that will be optimised out: */ extern __ro_after_init DECLARE_BITMAP(sve_vq_map, SVE_VQ_MAX); +extern __ro_after_init DECLARE_BITMAP(sve_vq_partial_map, SVE_VQ_MAX); extern void __percpu *efi_sve_state; #endif /* ! CONFIG_ARM64_SVE */ @@ -623,12 +629,6 @@ int sve_get_current_vl(void) return sve_prctl_status(0); } -/* - * Bitmap for temporary storage of the per-CPU set of supported vector lengths - * during secondary boot. - */ -static DECLARE_BITMAP(sve_secondary_vq_map, SVE_VQ_MAX); - static void sve_probe_vqs(DECLARE_BITMAP(map, SVE_VQ_MAX)) { unsigned int vq, vl; @@ -654,6 +654,7 @@ static void sve_probe_vqs(DECLARE_BITMAP(map, SVE_VQ_MAX)) void __init sve_init_vq_map(void) { sve_probe_vqs(sve_vq_map); + bitmap_copy(sve_vq_partial_map, sve_vq_map, SVE_VQ_MAX); } /* @@ -663,8 +664,11 @@ void __init sve_init_vq_map(void) */ void sve_update_vq_map(void) { - sve_probe_vqs(sve_secondary_vq_map); - bitmap_and(sve_vq_map, sve_vq_map, sve_secondary_vq_map, SVE_VQ_MAX); + DECLARE_BITMAP(tmp_map, SVE_VQ_MAX); + + sve_probe_vqs(tmp_map); + bitmap_and(sve_vq_map, sve_vq_map, tmp_map, SVE_VQ_MAX); + bitmap_or(sve_vq_partial_map, sve_vq_partial_map, tmp_map, SVE_VQ_MAX); } /* @@ -673,18 +677,48 @@ void sve_update_vq_map(void) */ int sve_verify_vq_map(void) { - int ret = 0; + DECLARE_BITMAP(tmp_map, SVE_VQ_MAX); + unsigned long b; - sve_probe_vqs(sve_secondary_vq_map); - bitmap_andnot(sve_secondary_vq_map, sve_vq_map, sve_secondary_vq_map, - SVE_VQ_MAX); - if (!bitmap_empty(sve_secondary_vq_map, SVE_VQ_MAX)) { + sve_probe_vqs(tmp_map); + + bitmap_complement(tmp_map, tmp_map, SVE_VQ_MAX); + if (bitmap_intersects(tmp_map, sve_vq_map, SVE_VQ_MAX)) { pr_warn("SVE: cpu%d: Required vector length(s) missing\n", smp_processor_id()); - ret = -EINVAL; + return -EINVAL; } - return ret; + if (!IS_ENABLED(CONFIG_KVM) || !is_hyp_mode_available()) + return 0; + + /* + * For KVM, it is necessary to ensure that this CPU doesn't + * support any vector length that guests may have probed as + * unsupported. + */ + + /* Recover the set of supported VQs: */ + bitmap_complement(tmp_map, tmp_map, SVE_VQ_MAX); + /* Find VQs supported that are not globally supported: */ + bitmap_andnot(tmp_map, tmp_map, sve_vq_map, SVE_VQ_MAX); + + /* Find the lowest such VQ, if any: */ + b = find_last_bit(tmp_map, SVE_VQ_MAX); + if (b >= SVE_VQ_MAX) + return 0; /* no mismatches */ + + /* + * Mismatches above sve_max_virtualisable_vl are fine, since + * no guest is allowed to configure ZCR_EL2.LEN to exceed this: + */ + if (sve_vl_from_vq(bit_to_vq(b)) <= sve_max_virtualisable_vl) { + pr_warn("SVE: cpu%d: Unsupported vector length(s) present\n", + smp_processor_id()); + return -EINVAL; + } + + return 0; } static void __init sve_efi_setup(void) @@ -751,6 +785,8 @@ u64 read_zcr_features(void) void __init sve_setup(void) { u64 zcr; + DECLARE_BITMAP(tmp_map, SVE_VQ_MAX); + unsigned long b; if (!system_supports_sve()) return; @@ -779,11 +815,31 @@ void __init sve_setup(void) */ sve_default_vl = find_supported_vector_length(64); + bitmap_andnot(tmp_map, sve_vq_partial_map, sve_vq_map, + SVE_VQ_MAX); + + b = find_last_bit(tmp_map, SVE_VQ_MAX); + if (b >= SVE_VQ_MAX) + /* No non-virtualisable VLs found */ + sve_max_virtualisable_vl = SVE_VQ_MAX; + else if (WARN_ON(b == SVE_VQ_MAX - 1)) + /* No virtualisable VLs? This is architecturally forbidden. */ + sve_max_virtualisable_vl = SVE_VQ_MIN; + else /* b + 1 < SVE_VQ_MAX */ + sve_max_virtualisable_vl = sve_vl_from_vq(bit_to_vq(b + 1)); + + if (sve_max_virtualisable_vl > sve_max_vl) + sve_max_virtualisable_vl = sve_max_vl; + pr_info("SVE: maximum available vector length %u bytes per vector\n", sve_max_vl); pr_info("SVE: default vector length %u bytes per vector\n", sve_default_vl); + /* KVM decides whether to support mismatched systems. Just warn here: */ + if (sve_max_virtualisable_vl < sve_max_vl) + pr_warn("SVE: unvirtualisable vector lengths present\n"); + sve_efi_setup(); } -- 2.1.4 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel