From nobody Thu Sep 19 01:11:04 2024 Received: from mail-pf1-f201.google.com (mail-pf1-f201.google.com [209.85.210.201]) (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 CC462181B89 for ; Fri, 26 Jul 2024 23:54:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722038044; cv=none; b=Ttnvyf0/wvgKxD3htgJpyQ2tDqBs7guH/HjKY1aCKhfNqaQ0k/IkW8iDAABRgV2Bsgf1BAJlBAxk5jvXxyaJXf8YGLxfsvfKx1YZ0+N7oAadK7FjGc3S5062NYEfEIXHbXnvCd8W9jmAHffIQI6cVqtlXQ+9ofM82V+8Jpf4ilg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722038044; c=relaxed/simple; bh=ekyGgwJW5KCFeLGIovEA7dKaEjIwCbNp1pdHY6eLnUg=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=iyUsPWPiRgKgKZ78aBqJ8nFoUfgarOH9aEl7HPyNdXg8PPAIoWVNTuTDaD67MzMCVsmD5coemoNSbGcKOKaIPwG0GTdtf7TsGo7s+gY2szpl8n/9A54YvnnPFe5SxqHsA1Ibc1FsQtRTQ5n8Vi4marERGOYvxBD69O5f99eqQbo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=EtumUVXI; arc=none smtp.client-ip=209.85.210.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="EtumUVXI" Received: by mail-pf1-f201.google.com with SMTP id d2e1a72fcca58-70ecd589debso373623b3a.2 for ; Fri, 26 Jul 2024 16:54:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1722038042; x=1722642842; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date:message-id:reply-to; bh=9zY2YEu1HUtjdcDr5plCoNlYuLGLbh4OhGnITp611eA=; b=EtumUVXI2jZeJVyXIOtCdc3ms6GfSXVKBvnpKwFMdWnOBYLK2R789/b+Hhq0JC5U5s eaktal8sdZdpzMU5ovrg2yMMyyeKlrS/xlRUfYQppWYAq69mi/k1X5QWseXP3Jepi1YQ XULdeW2trQHNILSouEZYBDOGBqQRqWQQ4v/EvxlUruo/xDYxKBcJTEU5ZH+JEKTai/Tz R3wg7aGnSY67KdY6DKx/mrKiWcSgqqpsHtOCyETPgjORhwvxk+VFQKRakqlpdS0MVWB7 HY2GS2iaWvMsxkCBLBixHsrHudit0DfsH5SjPsONZIBjyoYc3e4PjOdgfyFExEj24A5z wxNw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1722038042; x=1722642842; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=9zY2YEu1HUtjdcDr5plCoNlYuLGLbh4OhGnITp611eA=; b=pFBZrGi1DCmG3B+hDLmzdC3uBTChffyANtwjdBlBac278QoYyMAw7Wg759Y0hMObga O2qSakrnWEr4AZsC6qdWWa96g5NSZm0jVSIIrkMY3w3tGf4I7+Jzg6YRlMBYNPMI/wrn 3TzMBw0sNcoVvB4HcvZLhlB0SIBzrDEOHs6Mr3jdOCPrc2HM86TSEmCumBIg2cVYa7KL S4CqTmUgUEtjN5rjVUrqhYvDrIuDDWQPmRC84hYeWZ22hfI4I5uaVmNJMqya3zKvZMaZ YE60bkfWjFAD6WIP7ySvjU8RKegTqdAoypD1SZpRQcSSBqPMyfUe0b+jhdlq+cs+dQ+r p83Q== X-Forwarded-Encrypted: i=1; AJvYcCVamapJYljyhI8uHqn3g6AFzXtDdK2NTx1Af+cMWsNf+ECaigxK041vQblw1A3dyoofncEwNtuxmsS689YqUQUT8Xb2s4vfVtwgjHF4 X-Gm-Message-State: AOJu0Ywb8M9VEuespDH+rvxdB6kacd0W2+7xoj7vn3FVW3JqJADhUpqs r3uhV15CC/sGGwwJT6njrxRh5oLX+o6ur5Tj21zgLAujkQzNmLIKa7ASfiZgJTCmv3Fa8Z0GZTK q7g== X-Google-Smtp-Source: AGHT+IFj2ro53tB8A9NyZ1GYVrgqdx/ajbf6jMsbjIk3q7R62qDhpHqlToArJZlcHrNz2kHOoBaEKLt0+7c= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a05:6a00:66e5:b0:70d:27ca:96b8 with SMTP id d2e1a72fcca58-70ece926ad1mr25418b3a.0.1722038041966; Fri, 26 Jul 2024 16:54:01 -0700 (PDT) Reply-To: Sean Christopherson Date: Fri, 26 Jul 2024 16:51:50 -0700 In-Reply-To: <20240726235234.228822-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240726235234.228822-1-seanjc@google.com> X-Mailer: git-send-email 2.46.0.rc1.232.g9752f9e123-goog Message-ID: <20240726235234.228822-42-seanjc@google.com> Subject: [PATCH v12 41/84] KVM: x86/mmu: Mark pages/folios dirty at the origin of make_spte() From: Sean Christopherson To: Paolo Bonzini , Marc Zyngier , Oliver Upton , Tianrui Zhao , Bibo Mao , Huacai Chen , Michael Ellerman , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Sean Christopherson Cc: kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, David Matlack , David Stevens Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Move the marking of folios dirty from make_spte() out to its callers, which have access to the _struct page_, not just the underlying pfn. Once all architectures follow suit, this will allow removing KVM's ugly hack where KVM elevates the refcount of VM_MIXEDMAP pfns that happen to be struct page memory. Signed-off-by: Sean Christopherson --- arch/x86/kvm/mmu/mmu.c | 29 +++++++++++++++++++++++++++-- arch/x86/kvm/mmu/paging_tmpl.h | 5 +++++ arch/x86/kvm/mmu/spte.c | 11 ----------- 3 files changed, 32 insertions(+), 13 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 1cdd67707461..7e7b855ce1e1 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -2918,7 +2918,16 @@ static bool kvm_mmu_prefetch_sptes(struct kvm_vcpu *= vcpu, gfn_t gfn, u64 *sptep, for (i =3D 0; i < nr_pages; i++, gfn++, sptep++) { mmu_set_spte(vcpu, slot, sptep, access, gfn, page_to_pfn(pages[i]), NULL); - kvm_release_page_clean(pages[i]); + + /* + * KVM always prefetches writable pages from the primary MMU, + * and KVM can make its SPTE writable in the fast page, without + * notifying the primary MMU. Mark pages/folios dirty now to + * ensure file data is written back if it ends up being written + * by the guest. Because KVM's prefetching GUPs writable PTEs, + * the probability of unnecessary writeback is extremely low. + */ + kvm_release_page_dirty(pages[i]); } =20 return true; @@ -4314,7 +4323,23 @@ static u8 kvm_max_private_mapping_level(struct kvm *= kvm, kvm_pfn_t pfn, static void kvm_mmu_finish_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault, int r) { - kvm_release_pfn_clean(fault->pfn); + lockdep_assert_once(lockdep_is_held(&vcpu->kvm->mmu_lock) || + r =3D=3D RET_PF_RETRY); + + /* + * If the page that KVM got from the *primary MMU* is writable, and KVM + * installed or reused a SPTE, mark the page/folio dirty. Note, this + * may mark a folio dirty even if KVM created a read-only SPTE, e.g. if + * the GFN is write-protected. Folios can't be safely marked dirty + * outside of mmu_lock as doing so could race with writeback on the + * folio. As a result, KVM can't mark folios dirty in the fast page + * fault handler, and so KVM must (somewhat) speculatively mark the + * folio dirty if KVM could locklessly make the SPTE writable. + */ + if (!fault->map_writable || r =3D=3D RET_PF_RETRY) + kvm_release_pfn_clean(fault->pfn); + else + kvm_release_pfn_dirty(fault->pfn); } =20 static int kvm_mmu_faultin_pfn_private(struct kvm_vcpu *vcpu, diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h index b6897916c76b..2e2d87a925ac 100644 --- a/arch/x86/kvm/mmu/paging_tmpl.h +++ b/arch/x86/kvm/mmu/paging_tmpl.h @@ -953,6 +953,11 @@ static int FNAME(sync_spte)(struct kvm_vcpu *vcpu, str= uct kvm_mmu_page *sp, int spte_to_pfn(spte), spte, true, false, host_writable, &spte); =20 + /* + * There is no need to mark the pfn dirty, as the new protections must + * be a subset of the old protections, i.e. synchronizing a SPTE cannot + * change the SPTE from read-only to writable. + */ return mmu_spte_update(sptep, spte); } =20 diff --git a/arch/x86/kvm/mmu/spte.c b/arch/x86/kvm/mmu/spte.c index 9b8795bd2f04..2c5650390d3b 100644 --- a/arch/x86/kvm/mmu/spte.c +++ b/arch/x86/kvm/mmu/spte.c @@ -277,17 +277,6 @@ bool make_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_p= age *sp, mark_page_dirty_in_slot(vcpu->kvm, slot, gfn); } =20 - /* - * If the page that KVM got from the primary MMU is writable, i.e. if - * it's host-writable, mark the page/folio dirty. As alluded to above, - * folios can't be safely marked dirty in the fast page fault handler, - * and so KVM must (somewhat) speculatively mark the folio dirty even - * though it isn't guaranteed to be written as KVM won't mark the folio - * dirty if/when the SPTE is made writable. - */ - if (host_writable) - kvm_set_pfn_dirty(pfn); - *new_spte =3D spte; return wrprot; } --=20 2.46.0.rc1.232.g9752f9e123-goog