From patchwork Fri Jul 26 23:52:24 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sean Christopherson X-Patchwork-Id: 13743334 Received: from mail-yb1-f202.google.com (mail-yb1-f202.google.com [209.85.219.202]) (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 D351618FDD3 for ; Fri, 26 Jul 2024 23:55:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722038116; cv=none; b=kq+l+OdYfQiF2U5+xETEFKCcZs8dRvsKtTwQbaWbhjE2KzKJXJ57njiaxkZEjw6CK0mN0PT3b+vUIdR3znEwsp0NGIaq9NujpZPb14yHAe/cSXzmD0F1GwggQwDmVnrSBvn5gUWzsYWRL2diLorKJL4mLayHUweBaefalpIo+Ps= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722038116; c=relaxed/simple; bh=p0sbScV9KYWrdS1YnUq9iP3jaGBNbAWZ6v3m97jnfrM=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=jJQqxyn1jmT5TG/MrNg9IBPkf5YAOjMyiKuQayGsfZoTX5JR8+w3LErND58iInhHRzWpUC86i5RFWhlaCvvQua3Bzb9gM/ZoMSESuIBz/wQtzT9Cnov/VnTIH35Xq5/u4YX7ouQPx+O3Tp6REL+fU6K5I1rmMRs4RlPp2dGNVV4= 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=Rw3gWiwC; arc=none smtp.client-ip=209.85.219.202 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="Rw3gWiwC" Received: by mail-yb1-f202.google.com with SMTP id 3f1490d57ef6-e0b2fb62a07so450258276.0 for ; Fri, 26 Jul 2024 16:55:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1722038114; x=1722642914; 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=zSysp7FPh6wn+DolRHFxx8ZAZJRhLuISfWWp3RFo0OA=; b=Rw3gWiwCXZn+yAIRBBxOBVVq7qQjbcphCA3GjHPzQ7gO9dL5tKEufxJCJ7asjzpkeO llmmowxZpw8iLxtC9qk2EhjVJA5HdHCRrwcAKJNDfUkBN+0W7aZTXlghDJhmEALMY6dy Y16GaK06BKVbFand5e+W7GVUjUZTzGRooiB6ud42VYRUzGV3mryUyMK0NuCeS+ew0fj+ aVpGrUi74V7BumvPCvcKuZ1Xj5UTlerHGlKd+3fP8PVeW1vFcP87gk7HkPUXh8fToweZ tMmxlpZOm0F3b2YTDVtm00YwJkxJ28usGqldB5dcqiIlfkE9faLLzCEALOZU2b0J/bbE 06/Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1722038114; x=1722642914; 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=zSysp7FPh6wn+DolRHFxx8ZAZJRhLuISfWWp3RFo0OA=; b=r2u4nMwiolMqmWQtnSiy1t1rJnymv3GinPY92PUS/bHXQIdpQyjGGCv/fC3zKDTmi3 IrXUQRZ0rh8vPJBSqbMOPEuUn/89aOQDFeVU4SGKo5VcRc9froOWs7df7Dwr+NlOYLmA GRdNzye67mT9JouT7SJegBdQmGP+lPbO2z1+R7m1oEpUBYcVmAOFqqvIPWiJPBvtOFyQ TxFq+044Wz3iyQCNDnMlvAxXx25X5zGi4M3KVCpbaM+Z9b8+HL0ToZM70lez8LTyBhOC zvliEJAZzK6VSFHB6CySZbH1U1anUVLfOGLR6OZehhinj52t0gCYgUnjvO4pIkjar43k IAIw== X-Forwarded-Encrypted: i=1; AJvYcCViddM//jLnxLQvei8XvrMDPf1vZYJsngAvVIBjEY+/SUzD/W68ll61rp7AYYK5MofCNfunAmXSNzuf5QivXoSki4qkiTuB/73/1g== X-Gm-Message-State: AOJu0YzKnoPeQXAAZ1tJ01KYZKqBzSW2328Cmp5rgBZUQjR7RtmrmD9S JiXX0GQJMnA8SWTEreSblt1/OJEV+U37XgaW1rBWBShlT8RuNfHHjbBslqPezNmrB8L8gM3ZUEj 8vA== X-Google-Smtp-Source: AGHT+IHtdYLzf8VxCow9ze9t5PB7b90MwNFbCURT1XZzWgwcWEIftZd8Pqph9MK+hSFYPsX4JKQKNB1AEe8= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a05:6902:1889:b0:dfb:1147:cbaa with SMTP id 3f1490d57ef6-e0b5459b0b9mr34694276.10.1722038113838; Fri, 26 Jul 2024 16:55:13 -0700 (PDT) Reply-To: Sean Christopherson Date: Fri, 26 Jul 2024 16:52:24 -0700 In-Reply-To: <20240726235234.228822-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-mips@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: <20240726235234.228822-76-seanjc@google.com> Subject: [PATCH v12 75/84] KVM: Add support for read-only usage of gfn_to_page() 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 Rework gfn_to_page() to support read-only accesses so that it can be used by arm64 to get MTE tags out of guest memory. Opportunistically rewrite the comment to be even more stern about using gfn_to_page(), as there are very few scenarios where requiring a struct page is actually the right thing to do (though there are such scenarios). Add a FIXME to call out that KVM probably should be pinning pages, not just getting pages. Signed-off-by: Sean Christopherson --- include/linux/kvm_host.h | 7 ++++++- virt/kvm/kvm_main.c | 15 ++++++++------- 2 files changed, 14 insertions(+), 8 deletions(-) diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 91341cdc6562..f2d3c3c436cc 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -1198,7 +1198,12 @@ void kvm_arch_flush_shadow_memslot(struct kvm *kvm, int kvm_prefetch_pages(struct kvm_memory_slot *slot, gfn_t gfn, struct page **pages, int nr_pages); -struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn); +struct page *__gfn_to_page(struct kvm *kvm, gfn_t gfn, bool write); +static inline struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn) +{ + return __gfn_to_page(kvm, gfn, true); +} + unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn); unsigned long gfn_to_hva_prot(struct kvm *kvm, gfn_t gfn, bool *writable); unsigned long gfn_to_hva_memslot(struct kvm_memory_slot *slot, gfn_t gfn); diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index d0f55a6ecb31..16bc3ac3ff84 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -3174,25 +3174,26 @@ int kvm_prefetch_pages(struct kvm_memory_slot *slot, gfn_t gfn, EXPORT_SYMBOL_GPL(kvm_prefetch_pages); /* - * Do not use this helper unless you are absolutely certain the gfn _must_ be - * backed by 'struct page'. A valid example is if the backing memslot is - * controlled by KVM. Note, if the returned page is valid, it's refcount has - * been elevated by gfn_to_pfn(). + * Don't use this API unless you are absolutely, positively certain that KVM + * needs to get a struct page, e.g. to pin the page for firmware DMA. + * + * FIXME: Users of this API likely need to FOLL_PIN the page, not just elevate + * its refcount. */ -struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn) +struct page *__gfn_to_page(struct kvm *kvm, gfn_t gfn, bool write) { struct page *refcounted_page = NULL; struct kvm_follow_pfn kfp = { .slot = gfn_to_memslot(kvm, gfn), .gfn = gfn, - .flags = FOLL_WRITE, + .flags = write ? FOLL_WRITE : 0, .refcounted_page = &refcounted_page, }; (void)kvm_follow_pfn(&kfp); return refcounted_page; } -EXPORT_SYMBOL_GPL(gfn_to_page); +EXPORT_SYMBOL_GPL(__gfn_to_page); int __kvm_vcpu_map(struct kvm_vcpu *vcpu, gfn_t gfn, struct kvm_host_map *map, bool writable)