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Thu, 25 Apr 2019 08:55:34 +0000 (UTC) Subject: Re: [Xen-devel] [PATCH 1/3] xen/swiotlb: fix condition for calling xen_destroy_contiguous_region() To: Jan Beulich Cc: Stefano Stabellini , iommu@lists.linux-foundation.org, xen-devel , Boris Ostrovsky , Konrad Rzeszutek Wilk , lkml , stable@vger.kernel.org References: =?UTF-8?B?PDIwMTkwNDIzMTA1NDU3LjE3NTAy77+9Me+/vWpncm9zc0BzdXNl?= =?UTF-8?Q?=2ecom=3e_=3c20190423105457=2e17502-2-jgross=40suse=2ecom=3e_=3c5?= =?UTF-8?Q?CC175950200007800228E80=40suse=2ecom=3e?= From: Juergen Gross Openpgp: preference=signencrypt Autocrypt: addr=jgross@suse.com; prefer-encrypt=mutual; keydata= mQENBFOMcBYBCACgGjqjoGvbEouQZw/ToiBg9W98AlM2QHV+iNHsEs7kxWhKMjrioyspZKOB ycWxw3ie3j9uvg9EOB3aN4xiTv4qbnGiTr3oJhkB1gsb6ToJQZ8uxGq2kaV2KL9650I1SJve dYm8Of8Zd621lSmoKOwlNClALZNew72NjJLEzTalU1OdT7/i1TXkH09XSSI8mEQ/ouNcMvIJ NwQpd369y9bfIhWUiVXEK7MlRgUG6MvIj6Y3Am/BBLUVbDa4+gmzDC9ezlZkTZG2t14zWPvx XP3FAp2pkW0xqG7/377qptDmrk42GlSKN4z76ELnLxussxc7I2hx18NUcbP8+uty4bMxABEB AAG0H0p1ZXJnZW4gR3Jvc3MgPGpncm9zc0BzdXNlLmNvbT6JATkEEwECACMFAlOMcK8CGwMH CwkIBwMCAQYVCAIJCgsEFgIDAQIeAQIXgAAKCRCw3p3WKL8TL8eZB/9G0juS/kDY9LhEXseh mE9U+iA1VsLhgDqVbsOtZ/S14LRFHczNd/Lqkn7souCSoyWsBs3/wO+OjPvxf7m+Ef+sMtr0 G5lCWEWa9wa0IXx5HRPW/ScL+e4AVUbL7rurYMfwCzco+7TfjhMEOkC+va5gzi1KrErgNRHH kg3PhlnRY0Udyqx++UYkAsN4TQuEhNN32MvN0Np3WlBJOgKcuXpIElmMM5f1BBzJSKBkW0Jc Wy3h2Wy912vHKpPV/Xv7ZwVJ27v7KcuZcErtptDevAljxJtE7aJG6WiBzm+v9EswyWxwMCIO RoVBYuiocc51872tRGywc03xaQydB+9R7BHPuQENBFOMcBYBCADLMfoA44MwGOB9YT1V4KCy vAfd7E0BTfaAurbG+Olacciz3yd09QOmejFZC6AnoykydyvTFLAWYcSCdISMr88COmmCbJzn sHAogjexXiif6ANUUlHpjxlHCCcELmZUzomNDnEOTxZFeWMTFF9Rf2k2F0Tl4E5kmsNGgtSa aMO0rNZoOEiD/7UfPP3dfh8JCQ1VtUUsQtT1sxos8Eb/HmriJhnaTZ7Hp3jtgTVkV0ybpgFg w6WMaRkrBh17mV0z2ajjmabB7SJxcouSkR0hcpNl4oM74d2/VqoW4BxxxOD1FcNCObCELfIS auZx+XT6s+CE7Qi/c44ibBMR7hyjdzWbABEBAAGJAR8EGAECAAkFAlOMcBYCGwwACgkQsN6d 1ii/Ey9D+Af/WFr3q+bg/8v5tCknCtn92d5lyYTBNt7xgWzDZX8G6/pngzKyWfedArllp0Pn fgIXtMNV+3t8Li1Tg843EXkP7+2+CQ98MB8XvvPLYAfW8nNDV85TyVgWlldNcgdv7nn1Sq8g HwB2BHdIAkYce3hEoDQXt/mKlgEGsLpzJcnLKimtPXQQy9TxUaLBe9PInPd+Ohix0XOlY+Uk QFEx50Ki3rSDl2Zt2tnkNYKUCvTJq7jvOlaPd6d/W0tZqpyy7KVay+K4aMobDsodB3dvEAs6 ScCnh03dDAFgIq5nsB11j3KPKdVoPlfucX2c7kGNH+LUMbzqV6beIENfNexkOfxHf4kBrQQY AQgAIBYhBIUSZ3Lo9gSUpdCX97DendYovxMvBQJa3fDQAhsCAIEJELDendYovxMvdiAEGRYI AB0WIQRTLbB6QfY48x44uB6AXGG7T9hjvgUCWt3w0AAKCRCAXGG7T9hjvk2LAP99B/9FenK/ 1lfifxQmsoOrjbZtzCS6OKxPqOLHaY47BgEAqKKn36YAPpbk09d2GTVetoQJwiylx/Z9/mQI CUbQMg1pNQf9EjA1bNcMbnzJCgt0P9Q9wWCLwZa01SnQWFz8Z4HEaKldie+5bHBL5CzVBrLv 81tqX+/j95llpazzCXZW2sdNL3r8gXqrajSox7LR2rYDGdltAhQuISd2BHrbkQVEWD4hs7iV 1KQHe2uwXbKlguKPhk5ubZxqwsg/uIHw0qZDk+d0vxjTtO2JD5Jv/CeDgaBX4Emgp0NYs8IC UIyKXBtnzwiNv4cX9qKlz2Gyq9b+GdcLYZqMlIBjdCz0yJvgeb3WPNsCOanvbjelDhskx9gd 6YUUFFqgsLtrKpCNyy203a58g2WosU9k9H+LcheS37Ph2vMVTISMszW9W8gyORSgmw== Message-ID: <38c2907c-2749-e66c-1279-7d74bc20bc35@suse.com> Date: Thu, 25 Apr 2019 10:55:33 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Language: de-DE Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 25/04/2019 10:53, Jan Beulich wrote: >>>> On 23.04.19 at 12:54, wrote: >> --- a/drivers/xen/swiotlb-xen.c >> +++ b/drivers/xen/swiotlb-xen.c >> @@ -360,8 +360,8 @@ xen_swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr, >> /* Convert the size to actually allocated. */ >> size = 1UL << (order + XEN_PAGE_SHIFT); >> >> - if (((dev_addr + size - 1 <= dma_mask)) || >> - range_straddles_page_boundary(phys, size)) >> + if ((dev_addr + size - 1 <= dma_mask) && >> + !WARN_ON(range_straddles_page_boundary(phys, size))) >> xen_destroy_contiguous_region(phys, order); > > On the allocation side we have > > if (((dev_addr + size - 1 <= dma_mask)) && > !range_straddles_page_boundary(phys, size)) > *dma_handle = dev_addr; > else { > if (xen_create_contiguous_region(phys, order, > fls64(dma_mask), dma_handle) != 0) { > xen_free_coherent_pages(hwdev, size, ret, (dma_addr_t)phys, attrs); > return NULL; > } > } > > which is (as far as the function call is concerned) > > if ((dev_addr + size - 1 > dma_mask) || > range_straddles_page_boundary(phys, size)) > xen_create_contiguous_region(...); > > So I don't think your transformation is correct. Even worse, both > parts of the condition in xen_swiotlb_free_coherent() act on an > address that is the _result_ of the prior > xen_create_contiguous_region(), i.e. the address should always > match _both_ criteria anyway. Whereas what you really want is > undo the xen_create_contiguous_region() only when it actually > was called. Otherwise you also shatter contiguous allocations > that were contiguous already for other reasons (perhaps just > luck). Yes, that is what patch 3 does. Juergen