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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 35318C3DA49 for ; Thu, 25 Jul 2024 18:08:04 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A12366B0083; Thu, 25 Jul 2024 14:08:03 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9C3276B0085; Thu, 25 Jul 2024 14:08:03 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 88A9B6B0088; Thu, 25 Jul 2024 14:08:03 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 697CD6B0083 for ; Thu, 25 Jul 2024 14:08:03 -0400 (EDT) Received: from smtpin19.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id C635CC135D for ; Thu, 25 Jul 2024 18:08:02 +0000 (UTC) X-FDA: 82379058804.19.0FFFCA5 Received: from mail-pl1-f177.google.com (mail-pl1-f177.google.com [209.85.214.177]) by imf17.hostedemail.com (Postfix) with ESMTP id DC69940046 for ; Thu, 25 Jul 2024 18:08:00 +0000 (UTC) Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b="w4a43Aq/"; spf=pass (imf17.hostedemail.com: domain of dmatlack@google.com designates 209.85.214.177 as permitted sender) smtp.mailfrom=dmatlack@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1721930815; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=UUGaRPCQ3N3wWtHO14ZqED92UBSd1h87iBGfjwpcBN0=; b=MnbF87CDya5RsM2uwBSIGI1bcbm8RS91rum4AdnfXr5NRZKppWWSihk8zjbpx3eCo7/PhJ oW+anGPkMW0SuUss+szyM2Ila4JNH5BaWu9gRCOKP09gHIXJ+1F1vF98pldEqgYQ+b2L1T 9TH820sqyMYqVIWoeZ7M29yEhB0hd0o= ARC-Authentication-Results: i=1; imf17.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b="w4a43Aq/"; spf=pass (imf17.hostedemail.com: domain of dmatlack@google.com designates 209.85.214.177 as permitted sender) smtp.mailfrom=dmatlack@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1721930815; a=rsa-sha256; cv=none; b=IBAFtDwwCAmAxxMJ4qv4nsFV4gEqWZhnWJVycwuFtIx4mK1uEjiA02L0G6yCPeP00T2Kwj EXmvbhse/O7LBgdHtvkwLBUL8LexnHSkhcE6y1O9/tL+ZGNb2KhiyzsUDfLKhXUbOlP+Vv F/y9b1JvYBewHtHA1JzQLi8/DUobWWs= Received: by mail-pl1-f177.google.com with SMTP id d9443c01a7336-1fc5296e214so10840045ad.0 for ; Thu, 25 Jul 2024 11:08:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1721930879; x=1722535679; darn=kvack.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=UUGaRPCQ3N3wWtHO14ZqED92UBSd1h87iBGfjwpcBN0=; b=w4a43Aq/Lj6hiidAKjqIucD3iK+Ez4CPdBs96Ku16FbwVhkQoyhUH6Zl7Nm2wEZpXJ x54DQ8tKnH+neIh2MhsJX3GDW2D7PB+CTFQFbCFz4Nt7iPh3GNh1vpBaBgh03O9ZR0qG GwctXktuJ5oJVOqAk1Ha5d7DtbfADOOzNthKpZdoT9txDiy8biLBd1Rck5SlNBUh03Ul frPTRuuDXYUAFnf4gQbRbw1mb1hanktjXNz/NsxcHHoV2vPWY94slnL7K/ynyG3EV781 TsBy8ZIXnusyMWd8ql1gdk3a+mjOndM652LMNNUizljmWZbM6QBYlq8cn4d4fqQo48Nd Z+5w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1721930879; x=1722535679; 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=UUGaRPCQ3N3wWtHO14ZqED92UBSd1h87iBGfjwpcBN0=; b=Ty6pMDzEEzr9++C4cYkwDyGAxuK6oa8KgAL+ma4yEYIbRBOV2OvEQxz0q5IehleNcU swyoXaDxjinCO8njVdPvbl+mURY6NntzZ/BvpcbIMOgx9TGBf8Ttz/ShoG3kgVC1lJWq gEcgmDRliwtOvSX7aABXUMVtx1BgBFdZQ842PSIV3lNIoAjcIsB3GMUxM+4c9zK+aTWI LKxaTVLMqUADExk215TGAuBu96WudouugFPnZU2lA8d/He+Cl5GAKttFKCnzryGOQpiO /kI25EVsjbtga4/zktiK1fSPzjok+2vgJIuVQqKKkcTUhtw0sLLxmYdaz9ONmRLXspa+ KLsw== X-Forwarded-Encrypted: i=1; AJvYcCVP4gCKv0mPCv5hU9pWY2J11UAmESw/UAkmhBUqSMt28Xe5Gf153WWHXLJ0r6xpyoR9tcyKSKfZlTTT8rnRVINxsus= X-Gm-Message-State: AOJu0YyCV11hFWbjJb9lPvTbCx34cTP3OYMWCmlBYB6qqRxoTurqeUPh 9LpmENH83Umuif6vR93fJ5H03VuYEFyQMQUobMCyuTBtQzV/qmc1IfveNuldnw== X-Google-Smtp-Source: AGHT+IHI1A1tvfnC1v1eHXLnRKjVzRp5f2FjOQ5bxe8jqwJy1SWM+jZHo5hxZrA2PYuH6SKb8vBZaw== X-Received: by 2002:a17:903:1c4:b0:1fc:2ee3:d46f with SMTP id d9443c01a7336-1fed90b6bd7mr34131415ad.11.1721930878977; Thu, 25 Jul 2024 11:07:58 -0700 (PDT) Received: from google.com (61.139.125.34.bc.googleusercontent.com. [34.125.139.61]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-7a9f9ec7acdsm1454827a12.66.2024.07.25.11.07.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 25 Jul 2024 11:07:58 -0700 (PDT) Date: Thu, 25 Jul 2024 11:07:53 -0700 From: David Matlack To: James Houghton Cc: Andrew Morton , Paolo Bonzini , Ankit Agrawal , Axel Rasmussen , Catalin Marinas , David Rientjes , James Morse , Jason Gunthorpe , Jonathan Corbet , Marc Zyngier , Oliver Upton , Raghavendra Rao Ananta , Ryan Roberts , Sean Christopherson , Shaoqin Huang , Suzuki K Poulose , Wei Xu , Will Deacon , Yu Zhao , Zenghui Yu , kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v6 02/11] KVM: x86: Relax locking for kvm_test_age_gfn and kvm_age_gfn Message-ID: References: <20240724011037.3671523-1-jthoughton@google.com> <20240724011037.3671523-3-jthoughton@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240724011037.3671523-3-jthoughton@google.com> X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: DC69940046 X-Stat-Signature: j69un6pby9j75ys43mqh33eiinn9hqnd X-Rspam-User: X-HE-Tag: 1721930880-632702 X-HE-Meta: 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 LbISrUa1 rwj8sXDY5dEGz0JP0Vgy8DE2n29nKbOkHcqrZfeTsOlymEfYClxnQMMn7ZvUanxDCufPsnVkB6LVYD58cD68moga/17kmwv4JKwYerQ/Qit1njYOIV0/1Am31zWyoxdHZbtErVaOFWtn4fQRROpxFw9wQBaAUQjffG75rE8dMvbRDVTZ1vdsNMV+g8pdFwFpsAG7/nIqgcIQTpVU4kPEXnob+95wfM8eXNac/81gYzLx0vyGutvZPQeQFkZATYTJyFIo8BVFFFiotVhW1sUuiJtAwR/DTLnsPwRshRMCobuMSNSGMUhSeQeCq1Nyz2lMBfesDjoR06SAKS4TkKmKXXHGNXRmaxH9Nejr7ixgXH1DJwBvidz1+m+dgjm2d8oPJH8RFQkpBIF+QhFM= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2024-07-24 01:10 AM, James Houghton wrote: > Walk the TDP MMU in an RCU read-side critical section. This requires a > way to do RCU-safe walking of the tdp_mmu_roots; do this with a new > macro. The PTE modifications are now done atomically, and > kvm_tdp_mmu_spte_need_atomic_write() has been updated to account for the > fact that kvm_age_gfn can now lockless update the accessed bit and the > R/X bits). > > If the cmpxchg for marking the spte for access tracking fails, we simply > retry if the spte is still a leaf PTE. If it isn't, we return false > to continue the walk. > > Harvesting age information from the shadow MMU is still done while > holding the MMU write lock. > > Suggested-by: Yu Zhao > Signed-off-by: James Houghton Aside from the comment fixes below, Reviewed-by: David Matlack > --- > arch/x86/include/asm/kvm_host.h | 1 + > arch/x86/kvm/Kconfig | 1 + > arch/x86/kvm/mmu/mmu.c | 10 ++++- > arch/x86/kvm/mmu/tdp_iter.h | 27 +++++++------ > arch/x86/kvm/mmu/tdp_mmu.c | 67 +++++++++++++++++++++++++-------- > 5 files changed, 77 insertions(+), 29 deletions(-) > [...] > --- a/arch/x86/kvm/mmu/tdp_iter.h > +++ b/arch/x86/kvm/mmu/tdp_iter.h > @@ -25,6 +25,13 @@ static inline u64 kvm_tdp_mmu_write_spte_atomic(tdp_ptep_t sptep, u64 new_spte) > return xchg(rcu_dereference(sptep), new_spte); > } > > +static inline u64 tdp_mmu_clear_spte_bits_atomic(tdp_ptep_t sptep, u64 mask) > +{ > + atomic64_t *sptep_atomic = (atomic64_t *)rcu_dereference(sptep); > + > + return (u64)atomic64_fetch_and(~mask, sptep_atomic); > +} > + > static inline void __kvm_tdp_mmu_write_spte(tdp_ptep_t sptep, u64 new_spte) > { > KVM_MMU_WARN_ON(is_ept_ve_possible(new_spte)); > @@ -32,10 +39,11 @@ static inline void __kvm_tdp_mmu_write_spte(tdp_ptep_t sptep, u64 new_spte) > } > > /* > - * SPTEs must be modified atomically if they are shadow-present, leaf > - * SPTEs, and have volatile bits, i.e. has bits that can be set outside > - * of mmu_lock. The Writable bit can be set by KVM's fast page fault > - * handler, and Accessed and Dirty bits can be set by the CPU. > + * SPTEs must be modified atomically if they have bits that can be set outside > + * of the mmu_lock. This can happen for any shadow-present leaf SPTEs, as the > + * Writable bit can be set by KVM's fast page fault handler, the Accessed and > + * Dirty bits can be set by the CPU, and the Accessed and R/X bits can be "R/X bits" should be "W/R/X bits". > + * cleared by age_gfn_range. nit: "age_gfn_range()"