From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 874B11CCB40 for ; Fri, 28 Feb 2025 21:15:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740777313; cv=none; b=JIo2UPimlqjimRFZPl2Zb57vTiKFhSaALn3Y74U5icn1UsCvYPvDtveQ0aBSOI45mrV1/9Alqd2gYcB4U8wTiGFQRmCWj6jYgyc6Ns1lBqY3JBC7YufCthhZo2N+b9IsTzFC20+4LigsTUog5IrAI05lDJPOpFY+FHl8o0IGiJU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740777313; c=relaxed/simple; bh=wyc6gBDTrziydpuK61JRdtvkYp6zQV0x/t8ufLMZr4I=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=V/KtLNTiS6db07+9GWYHEfi/Ym24HNXz6iZTZb0TtWTGREhUBM58Rd5tfxKd/arBJ8e1bvBdnj85vKqiWT1fxoKGrJrGiwwx0d2xB426O3yRNS6pokT9AELwdJBUH6avpIJG6sMkWMJqxQ/VPEMllYB+JRfk0a77djHOhKkADUE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=XRsW53KI; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="XRsW53KI" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1740777309; h=from:from: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:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=mRmrDjDqYaNeAPcUDExcWiFekmRwtmxV95n5m+IeDe0=; b=XRsW53KIb38Jz5DB5ioz0bzncJHvQt9VIsTt55WCpiiSStp3IkuypigWmio388YbF0JrKE GFguh/LXPzGgtVsL0VhaydyVus3aLzlABcm08VVKJXXjugdZ09yOS5XZMpEgjuc4LjRePX IWCsgDZhIBEPxaQ6k1vil13w0J29vck= Received: from mail-wr1-f71.google.com (mail-wr1-f71.google.com [209.85.221.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-643-v4t3Qlf8OnaeK1KJMB1RWw-1; Fri, 28 Feb 2025 16:15:07 -0500 X-MC-Unique: v4t3Qlf8OnaeK1KJMB1RWw-1 X-Mimecast-MFC-AGG-ID: v4t3Qlf8OnaeK1KJMB1RWw_1740777306 Received: by mail-wr1-f71.google.com with SMTP id ffacd0b85a97d-390e62ef5f6so928810f8f.2 for ; Fri, 28 Feb 2025 13:15:07 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1740777306; x=1741382106; h=content-transfer-encoding:in-reply-to:organization:autocrypt :content-language:from:references:cc:to:subject:user-agent :mime-version:date:message-id:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=mRmrDjDqYaNeAPcUDExcWiFekmRwtmxV95n5m+IeDe0=; b=F29bU8RmMFvKwmVhJznacuTeUpP2L+TpKu9M4Rqcv8tfprhcJ0qQItm7tZwrC7Oc3X jMb9AHmXAc0S341W1phCjvv3+Dh5ZVKUsPdWrJrAEWbg8PsNZx75taSf2rZP0RDzRufw SKFkXiMTocDRYqpsVx2IUa/y5DmxnOy7o0uVZpKaxVQW0A/7UzOeYsbg5FaMab131N5Z 1EyWGUA71fmV6hgzoycV5pyZrb+jL6Mp5Gp86ve+mRmt3XSujuh3itWiLMTeU0KnBRO4 FQYuWDH/ReGW7PThnSYtsKO5rSd/WOlTWkac4JCEjc6zS6N6qQ1iX7y6y8bpBogMOOuR w6Iw== X-Gm-Message-State: AOJu0YwLKU+lr3eV1Y00BkZKqtVDHuavAu4ZgLG8FcQdITQepzMlg/QZ Wn39NrP/k2/DwFOr/DYWluTK+7mbX4O9Ds57C5oQPTyya5A9bxgqRzOkIJav9eBNzLQ0Mm9ds8f zV32u8diyM0kacPi3ln86px6vn04CbgDkKY9lyOzL2MTlLt2sJZC6pS0yP/j8Cw== X-Gm-Gg: ASbGncs6l//YnWtQDbTt8kwlU65kQi2p72vbxkCjPbLudlNJUD+JPNvUzxw1HD+Ovii Pxqx4PWBMS21LEY2Sx/2S2myNlH3zlIyJOqQQTxG1ChrQz4gBjmJbc7QIH9HLZ6jNjYteF19d6R 97NeU3A1AiDLu3ZwCh7dkoCR9PIV/KWuFNhFXWP7T0ew5oH1jvzwXCQXoprbMZBDcchDkeHcf2N EOqoWuAbfDC0/UJwKcKXp1spPEs1x98Ym3u7ZjmL8FDJ6BQeHl1TOXr4xhTeqey4uPJdw1dfEfi hPMl/Phb/YnAzYLcTJfrXKqeXCS7C1Vr/Kks5opGwRnjAAUV080ekE53dmyvRL5nb9ajmKd8vg+ BKp+F1WcmZ5wP6TLcAlyllCPAli6Ij0Z86HRe3jH9wuo= X-Received: by 2002:a5d:47c3:0:b0:38d:ddf2:afe9 with SMTP id ffacd0b85a97d-390ec7c8ff5mr3640474f8f.1.1740777306493; Fri, 28 Feb 2025 13:15:06 -0800 (PST) X-Google-Smtp-Source: AGHT+IF9gz1ryGr92P/e9/0BEkkAs09/gylzMPlvYgXn18P/ISKKMsbdwmGytpizF7wukm38O7pqFg== X-Received: by 2002:a5d:47c3:0:b0:38d:ddf2:afe9 with SMTP id ffacd0b85a97d-390ec7c8ff5mr3640457f8f.1.1740777306123; Fri, 28 Feb 2025 13:15:06 -0800 (PST) Received: from ?IPV6:2003:d8:2f36:d800:164f:7689:99fe:7f58? (p200300d82f36d800164f768999fe7f58.dip0.t-ipconnect.de. [2003:d8:2f36:d800:164f:7689:99fe:7f58]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-390e484452asm6326697f8f.61.2025.02.28.13.15.05 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 28 Feb 2025 13:15:05 -0800 (PST) Message-ID: <370231a1-af36-46ca-a87c-ce1929473c1d@redhat.com> Date: Fri, 28 Feb 2025 22:15:04 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/1] KVM: s390: pv: fix race when making a page secure To: Claudio Imbrenda , kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, frankja@linux.ibm.com, borntraeger@de.ibm.com, nrb@linux.ibm.com, seiden@linux.ibm.com, nsg@linux.ibm.com, schlameuss@linux.ibm.com, hca@linux.ibm.com References: <20250227130954.440821-1-imbrenda@linux.ibm.com> <20250227130954.440821-2-imbrenda@linux.ibm.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <20250227130954.440821-2-imbrenda@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 27.02.25 14:09, Claudio Imbrenda wrote: > Holding the pte lock for the page that is being converted to secure is > needed to avoid races. A previous commit removed the locking, which > caused issues. Fix by locking the pte again. > > Fixes: 5cbe24350b7d ("KVM: s390: move pv gmap functions into kvm") > Reported-by: David Hildenbrand > Signed-off-by: Claudio Imbrenda Tested with shmem / memory-backend-memfd that ends up using large folios / THPs. Tested-by: David Hildenbrand Reviewed-by: David Hildenbrand Two comments below. [...] > + > +int make_hva_secure(struct mm_struct *mm, unsigned long hva, struct uv_cb_header *uvcb) > +{ > + struct folio *folio; > + spinlock_t *ptelock; > + pte_t *ptep; > + int rc; > + > + ptep = get_locked_valid_pte(mm, hva, &ptelock); > + if (!ptep) > + return -ENXIO; > + > + folio = page_folio(pte_page(*ptep)); > + folio_get(folio); Grabbing a folio reference is only required if you want to keep using the folio after the pte_unmap_unlock. While the PTL is locked it cannot vanish. So consider grabbing a reference only before dropping the PTL and you inted to call kvm_s390_wiggle_split_folio(). Then, you would effectively not require these two atomics on the expected hot path. (I recall that the old code did that) > + /* > + * Secure pages cannot be huge and userspace should not combine both. > + * In case userspace does it anyway this will result in an -EFAULT for > + * the unpack. The guest is thus never reaching secure mode. > + * If userspace plays dirty tricks and decides to map huge pages at a > + * later point in time, it will receive a segmentation fault or > + * KVM_RUN will return -EFAULT. > + */ > + if (folio_test_hugetlb(folio)) > + rc = -EFAULT; > + else if (folio_test_large(folio)) > + rc = -E2BIG; > + else if (!pte_write(*ptep)) > + rc = -ENXIO; > + else > + rc = make_folio_secure(mm, folio, uvcb); > + pte_unmap_unlock(ptep, ptelock); > + > + if (rc == -E2BIG || rc == -EBUSY) > + rc = kvm_s390_wiggle_split_folio(mm, folio, rc == -E2BIG); > + folio_put(folio); > + > + return rc; > +} > +EXPORT_SYMBOL_GPL(make_hva_secure); > > /* > * To be called with the folio locked or with an extra reference! This will > diff --git a/arch/s390/kvm/gmap.c b/arch/s390/kvm/gmap.c > index 02adf151d4de..c08950b4301c 100644 There is one remaining reference to __gmap_make_secure, which you remove: $ git grep __gmap_make_secure arch/s390/kvm/gmap.c: * Return: 0 on success, < 0 in case of error (see __gmap_make_secure()). -- Cheers, David / dhildenb