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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 86144C00528 for ; Wed, 19 Jul 2023 17:47:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230181AbjGSRrt (ORCPT ); Wed, 19 Jul 2023 13:47:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36926 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229990AbjGSRrs (ORCPT ); Wed, 19 Jul 2023 13:47:48 -0400 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8B13B1FDD for ; Wed, 19 Jul 2023 10:47:44 -0700 (PDT) Received: by mail-yb1-xb4a.google.com with SMTP id 3f1490d57ef6-c647150c254so1744406276.1 for ; Wed, 19 Jul 2023 10:47:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1689788863; x=1692380863; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:from:to:cc:subject:date:message-id :reply-to; bh=ZrpSlfvy8CWa29HQgq0qreuIOXt/Wldn9lf0s+IQ19g=; b=X9ynW0ej8481ncb+JbSIL8euZe2mr5ac0SQN0lLCVOPeUWz8gBSwzlmF4TS+pmsHcD ZHvVpvYsxfXcuGN+7iAna+BjVzlQUdXfzbNxlCS0j99kNjn4uiKYJhxoW/wLZRZhGth6 SbpazT26VqyLHMq6YpzbXDxi+oMw3HYZStI2pQTTUoLLoHXhI/Fn5BDIc8VD0DBHnb5o tff0t0H4OQwlS8KfnNmKRSLobGStUKs9j2oknxZFFagCPmr5LE+cTEI4/QNQaG1bCtL1 cIfSi8x3D97snfz5OpAaFyM4T1btS6Fnjj3oZZvzbB3+DHeSFy4bNTnAooGpizTyMK76 Nfxw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1689788863; x=1692380863; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=ZrpSlfvy8CWa29HQgq0qreuIOXt/Wldn9lf0s+IQ19g=; b=FODYnWybzS2i0ze3Lml11qAe4YPbLnUvfOgvW3GTBvvSf1dQjrzASrcKythhjsKikk dMv8BxdUaS+vwaKX7yZ5rNTUwEYI32RKpjRjACP6lthCU69sgORvHZkVVELOp/D+lt0b fqeo7Hr1occ/mKomx24G6S+KbjwHkE7sm4x9t4JfJxLT6CXTJFJvhIlkFOdR/9kwe4XC yWtdvShcsJqOfSRo/yygwKFSJihDtWt+Cy+OwDTv0xqmkXEA7FOwTNnyYe3i4kSpXNAD cVk4gQOqWM14uBkMxRQCAyfocgoaALeZ+Et0jQ9UcprzLe4f7UUFDZTHb5Uje4UBQOcM 1r8g== X-Gm-Message-State: ABy/qLYoOAnzXmOxzG0E3JCM5xnaV8a0hcimgwqYdZQhVR4VQGrnQ2Bo MDnDddEHCmivIlGC2ooXy6f6yLgHh5s= X-Google-Smtp-Source: APBJJlFlYUVvIIObTojpJ8UchQ4CwQtQGAVrCh++KpJ7LgJpdZRIA9xQwbGLQUVWTMKWnIrBZUJv99cvfhs= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a25:f509:0:b0:ca3:3341:6315 with SMTP id a9-20020a25f509000000b00ca333416315mr42238ybe.0.1689788863726; Wed, 19 Jul 2023 10:47:43 -0700 (PDT) Date: Wed, 19 Jul 2023 10:47:41 -0700 In-Reply-To: Mime-Version: 1.0 References: <20230718234512.1690985-1-seanjc@google.com> <20230718234512.1690985-13-seanjc@google.com> Message-ID: Subject: Re: [RFC PATCH v11 12/29] KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory From: Sean Christopherson To: Vishal Annapurve Cc: Paolo Bonzini , Marc Zyngier , Oliver Upton , Huacai Chen , Michael Ellerman , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , "Matthew Wilcox (Oracle)" , Andrew Morton , Paul Moore , James Morris , "Serge E. Hallyn" , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, Chao Peng , Fuad Tabba , Jarkko Sakkinen , Yu Zhang , Ackerley Tng , Maciej Szmigiero , Vlastimil Babka , David Hildenbrand , Quentin Perret , Michael Roth , Wang , Liam Merwick , Isaku Yamahata , "Kirill A . Shutemov" Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org On Wed, Jul 19, 2023, Vishal Annapurve wrote: > On Tue, Jul 18, 2023 at 4:49=E2=80=AFPM Sean Christopherson wrote: > > ... > > +static int kvm_gmem_error_page(struct address_space *mapping, struct p= age *page) > > +{ > > + struct list_head *gmem_list =3D &mapping->private_list; > > + struct kvm_memory_slot *slot; > > + struct kvm_gmem *gmem; > > + unsigned long index; > > + pgoff_t start, end; > > + gfn_t gfn; > > + > > + filemap_invalidate_lock_shared(mapping); > > + > > + start =3D page->index; > > + end =3D start + thp_nr_pages(page); > > + > > + list_for_each_entry(gmem, gmem_list, entry) { > > + xa_for_each_range(&gmem->bindings, index, slot, start, = end - 1) { > > + for (gfn =3D start; gfn < end; gfn++) { > > + if (WARN_ON_ONCE(gfn < slot->base_gfn |= | > > + gfn >=3D slot->base_gfn= + slot->npages)) > > + continue; > > + > > + /* > > + * FIXME: Tell userspace that the *priv= ate* > > + * memory encountered an error. > > + */ > > + send_sig_mceerr(BUS_MCEERR_AR, > > + (void __user *)gfn_to_h= va_memslot(slot, gfn), > > + PAGE_SHIFT, current); >=20 > Does it make sense to replicate what happens with MCE handling on > tmpfs backed guest memory: > 1) Unmap gpa from guest > 2) On the next guest EPT fault, exit to userspace to handle/log the > mce error for the gpa. Hmm, yes, that would be much better. Ah, and kvm_gmem_get_pfn() needs to c= heck folio_test_hwpoison() and potentially PageHWPoison(). E.g. if the folio is= huge, KVM needs to restrict the mapping to order-0 (target page isn't poisoned), = or return KVM_PFN_ERR_HWPOISON (taget page IS poisoned). Alternatively, KVM could punch a hole in kvm_gmem_error_page(), but I don't= think we want to do that because that would prevent forwarding the #MC to the gue= st.