From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f202.google.com (mail-pl1-f202.google.com [209.85.214.202]) (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 DED771DE3CA for ; Mon, 6 Jan 2025 18:57:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.202 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736189876; cv=none; b=H0kPzv78P5SXqdL6KAfaOTQF2/Z+C1SyHG8wJDg9FYjZ3+cqpyOuJKSYd9fcEPnGku2XXKCEoL4f1n5mD8LF+VWwmPcPML9UdTQZRIdcb8h2ubM0ny+F0RqBichWz1beUY7OBHc6sFLG4Z8HK76Dy/bwKoZg8seq4M4tnC5RXeU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736189876; c=relaxed/simple; bh=2OZKrS1dUkLlPuhPdhwGi7QnWZ+8XGoT1QDIIrdkEpI=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=SkQYYZcv1L+7d/n7nwCeq9bjYmQ4EDwsMBRrYqPSPc0E8HhDfnuqW5HQruhAzwgKm17FTJRFkgj4jSFBm7NX8SJsG1b2e0cKQwX6u1w+0YyfRg5XcUv0+g1nXWZN/4PqYrp1W36r3y6SQBIEIHWVggriCbJDDkXO8S/Fi3deZH8= 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=QR4TK6y0; arc=none smtp.client-ip=209.85.214.202 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="QR4TK6y0" Received: by mail-pl1-f202.google.com with SMTP id d9443c01a7336-2161d185f04so153175875ad.3 for ; Mon, 06 Jan 2025 10:57:54 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1736189874; x=1736794674; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=/aNADIekx2j0/enI87SMjtmQjX7teTUCuYI/dNHjl3o=; b=QR4TK6y0Qy0ZduGMCFwtPrdZwwEv46yflW88CuxZEuVghrJdVaEZsNQromlJaeW9X5 LqFkZr/RTVLO3QiG6mw/Pxrr9OHVIw1aTlzjaWeRQgKOcU/NXzH64o9/xFN34mn1D5Mg rHpjVRR40CDlpxeEQ1qXa0QVQpaoSKXTKGcLwTBGASa0InbIBUCZxD49IgVMb5jeyW/C gvKNq/+aclsH97g5pwBoKBhIXu3jC0ralbDQb4B2k8newfJi64TAr2x3OE2079y0FWw+ /JbVv1AubaMTmTOxdT3fhfAZZetyNf/ojiCUwT8iZelu/TaRbGymbUoYxyEvn59wm0jm HnMw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1736189874; x=1736794674; h=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=/aNADIekx2j0/enI87SMjtmQjX7teTUCuYI/dNHjl3o=; b=rpPNuR48JaR4LiehEQ3pD/rjtEALJ7VIWshnemzGWLrQgeX/JMrjx3dlKF1ZY23Xh9 jMcGr/64cBjuCfCGQV/Kv2NVpk/WAriMnN6gHuehl+Oa3NTFzvhGZiszBJeoAtvDp2GW 4iWHnWu8QgyKvw6fXHil8xqpcX6H02WHsc3SeECZV/8dBx5n1jqy3GdCCsoQ5oQR8zzX V3yPwb7eguQfSEIfNhDjRLuZgbZMp56jeEM9oxnnTQYXwyviDxmqxrhWWVvCTiDh1CXV JkO/c11XdYcfKtOW94cwrt/k54BMBxV/4V1bX7Y15PXWGetOdYe+Cri0XIqj/TKgIYiP 7CDQ== X-Forwarded-Encrypted: i=1; AJvYcCV/jIOyz1ReAD+DCr9tIfDImYlElveIG9VpEe5snEm2vG43PJOJCdfl3TZvo3FGdSrVQIs=@vger.kernel.org X-Gm-Message-State: AOJu0Yw32Bs5DVeKyk385voBo/hc7azg8Sb8FrFq3B9W1gYXLDOV2po/ JG5qSZRVAHKWoIpMdv/EXJ9NI9oNHlcRfjGrUGuNirXelaMMBeV0ePB+8QklHjPuUBW48n1dwbl yHA== X-Google-Smtp-Source: AGHT+IFTUQyqLv9XSGGLv1fnVkWYgSUL4cT3Eg9R6oafiMKaRGpJd6axUPFHZbm1bK48Dbcs7JdFs6gpXoI= X-Received: from pgbcv4.prod.google.com ([2002:a05:6a02:4204:b0:7fd:4d08:df94]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a20:8412:b0:1e1:b727:1801 with SMTP id adf61e73a8af0-1e5e07a55e8mr87767148637.27.1736189874330; Mon, 06 Jan 2025 10:57:54 -0800 (PST) Date: Mon, 6 Jan 2025 10:57:53 -0800 In-Reply-To: <20250101064928.389504-1-pbonzini@redhat.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250101064928.389504-1-pbonzini@redhat.com> Message-ID: Subject: Re: [PATCH] KVM: allow NULL writable argument to __kvm_faultin_pfn From: Sean Christopherson To: Paolo Bonzini Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Christian Zigotzky , linuxppc-dev@lists.ozlabs.org, regressions@lists.linux.dev Content-Type: text/plain; charset="us-ascii" On Wed, Jan 01, 2025, Paolo Bonzini wrote: > kvm_follow_pfn() is able to work with NULL in the .map_writable field > of the homonymous struct. But __kvm_faultin_pfn() rejects the combo > despite KVM for e500 trying to use it. Indeed .map_writable is not > particularly useful if the flags include FOLL_WRITE and readonly > guest memory is not supported, so add support to __kvm_faultin_pfn() > for this case. I would prefer to keep the sanity check to minimize the risk of a page fault handler not supporting opportunistic write mappings. e500 is definitely the odd one out here. What about adding a dedicated wrapper for getting a writable PFN? E.g. (untested) --- arch/powerpc/kvm/e500_mmu_host.c | 2 +- arch/x86/kvm/vmx/vmx.c | 3 +-- include/linux/kvm_host.h | 8 ++++++++ 3 files changed, 10 insertions(+), 3 deletions(-) diff --git a/arch/powerpc/kvm/e500_mmu_host.c b/arch/powerpc/kvm/e500_mmu_host.c index e5a145b578a4..2251bb30b8ec 100644 --- a/arch/powerpc/kvm/e500_mmu_host.c +++ b/arch/powerpc/kvm/e500_mmu_host.c @@ -444,7 +444,7 @@ static inline int kvmppc_e500_shadow_map(struct kvmppc_vcpu_e500 *vcpu_e500, if (likely(!pfnmap)) { tsize_pages = 1UL << (tsize + 10 - PAGE_SHIFT); - pfn = __kvm_faultin_pfn(slot, gfn, FOLL_WRITE, NULL, &page); + pfn = kvm_faultin_writable_pfn(slot, gfn, &page); if (is_error_noslot_pfn(pfn)) { if (printk_ratelimit()) pr_err("%s: real page not found for gfn %lx\n", diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 893366e53732..7012b583f2e8 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -6800,7 +6800,6 @@ void vmx_set_apic_access_page_addr(struct kvm_vcpu *vcpu) struct page *refcounted_page; unsigned long mmu_seq; kvm_pfn_t pfn; - bool writable; /* Defer reload until vmcs01 is the current VMCS. */ if (is_guest_mode(vcpu)) { @@ -6836,7 +6835,7 @@ void vmx_set_apic_access_page_addr(struct kvm_vcpu *vcpu) * controls the APIC-access page memslot, and only deletes the memslot * if APICv is permanently inhibited, i.e. the memslot won't reappear. */ - pfn = __kvm_faultin_pfn(slot, gfn, FOLL_WRITE, &writable, &refcounted_page); + pfn = kvm_faultin_writable_pfn(slot, gfn, &refcounted_page); if (is_error_noslot_pfn(pfn)) return; diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index c788d0bd952a..b0af7c7f99da 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -1287,6 +1287,14 @@ static inline kvm_pfn_t kvm_faultin_pfn(struct kvm_vcpu *vcpu, gfn_t gfn, write ? FOLL_WRITE : 0, writable, refcounted_page); } +static inline kvm_pfn_t kvm_faultin_writable_pfn(const struct kvm_memory_slot *slot, + gfn_t gfn, struct page **refcounted_page) +{ + bool writable; + + return __kvm_faultin_pfn(slot, gfn, FOLL_WRITE, &writable, refcounted_page); +} + int kvm_read_guest_page(struct kvm *kvm, gfn_t gfn, void *data, int offset, int len); int kvm_read_guest(struct kvm *kvm, gpa_t gpa, void *data, unsigned long len); base-commit: 2c3412e999738bfd60859c493ff47f5c268814a3 --