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[83.51.162.1]) by smtp.gmail.com with ESMTPSA id k185sm14220080wmk.47.2020.06.26.05.45.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 26 Jun 2020 05:45:47 -0700 (PDT) Subject: Re: [PATCH 04/17] block/nvme: Be explicit we share NvmeIdCtrl / NvmeIdNs structures To: Stefan Hajnoczi References: <20200625184838.28172-1-philmd@redhat.com> <20200625184838.28172-5-philmd@redhat.com> <20200626111905.GK281902@stefanha-x1.localdomain> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Autocrypt: addr=philmd@redhat.com; keydata= mQINBDXML8YBEADXCtUkDBKQvNsQA7sDpw6YLE/1tKHwm24A1au9Hfy/OFmkpzo+MD+dYc+7 bvnqWAeGweq2SDq8zbzFZ1gJBd6+e5v1a/UrTxvwBk51yEkadrpRbi+r2bDpTJwXc/uEtYAB GvsTZMtiQVA4kRID1KCdgLa3zztPLCj5H1VZhqZsiGvXa/nMIlhvacRXdbgllPPJ72cLUkXf z1Zu4AkEKpccZaJspmLWGSzGu6UTZ7UfVeR2Hcc2KI9oZB1qthmZ1+PZyGZ/Dy+z+zklC0xl XIpQPmnfy9+/1hj1LzJ+pe3HzEodtlVA+rdttSvA6nmHKIt8Ul6b/h1DFTmUT1lN1WbAGxmg CH1O26cz5nTrzdjoqC/b8PpZiT0kO5MKKgiu5S4PRIxW2+RA4H9nq7nztNZ1Y39bDpzwE5Sp bDHzd5owmLxMLZAINtCtQuRbSOcMjZlg4zohA9TQP9krGIk+qTR+H4CV22sWldSkVtsoTaA2 qNeSJhfHQY0TyQvFbqRsSNIe2gTDzzEQ8itsmdHHE/yzhcCVvlUzXhAT6pIN0OT+cdsTTfif MIcDboys92auTuJ7U+4jWF1+WUaJ8gDL69ThAsu7mGDBbm80P3vvUZ4fQM14NkxOnuGRrJxO qjWNJ2ZUxgyHAh5TCxMLKWZoL5hpnvx3dF3Ti9HW2dsUUWICSQARAQABtDJQaGlsaXBwZSBN YXRoaWV1LURhdWTDqSAoUGhpbCkgPHBoaWxtZEByZWRoYXQuY29tPokCVQQTAQgAPwIbDwYL CQgHAwIGFQgCCQoLBBYCAwECHgECF4AWIQSJweePYB7obIZ0lcuio/1u3q3A3gUCXsfWwAUJ KtymWgAKCRCio/1u3q3A3ircD/9Vjh3aFNJ3uF3hddeoFg1H038wZr/xi8/rX27M1Vj2j9VH 0B8Olp4KUQw/hyO6kUxqkoojmzRpmzvlpZ0cUiZJo2bQIWnvScyHxFCv33kHe+YEIqoJlaQc JfKYlbCoubz+02E2A6bFD9+BvCY0LBbEj5POwyKGiDMjHKCGuzSuDRbCn0Mz4kCa7nFMF5Jv piC+JemRdiBd6102ThqgIsyGEBXuf1sy0QIVyXgaqr9O2b/0VoXpQId7yY7OJuYYxs7kQoXI 6WzSMpmuXGkmfxOgbc/L6YbzB0JOriX0iRClxu4dEUg8Bs2pNnr6huY2Ft+qb41RzCJvvMyu gS32LfN0bTZ6Qm2A8ayMtUQgnwZDSO23OKgQWZVglGliY3ezHZ6lVwC24Vjkmq/2yBSLakZE 6DZUjZzCW1nvtRK05ebyK6tofRsx8xB8pL/kcBb9nCuh70aLR+5cmE41X4O+MVJbwfP5s/RW 9BFSL3qgXuXso/3XuWTQjJJGgKhB6xXjMmb1J4q/h5IuVV4juv1Fem9sfmyrh+Wi5V1IzKI7 RPJ3KVb937eBgSENk53P0gUorwzUcO+ASEo3Z1cBKkJSPigDbeEjVfXQMzNt0oDRzpQqH2vp apo2jHnidWt8BsckuWZpxcZ9+/9obQ55DyVQHGiTN39hkETy3Emdnz1JVHTU0Q== Message-ID: Date: Fri, 26 Jun 2020 14:45:45 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200626111905.GK281902@stefanha-x1.localdomain> Content-Language: en-US Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=philmd@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=205.139.110.61; envelope-from=philmd@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/26 02:19:36 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Fam Zheng , Kevin Wolf , qemu-block@nongnu.org, qemu-devel@nongnu.org, Max Reitz , Maxim Levitsky Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 6/26/20 1:19 PM, Stefan Hajnoczi wrote: > On Thu, Jun 25, 2020 at 08:48:25PM +0200, Philippe Mathieu-Daudé wrote: >> We allocate an unique chunk of memory then use it for two >> different structures. Introduce the 'idsz_max' variable to >> hold the maximum size, to make it clearer the size is enough >> to hold the two structures. >> >> Signed-off-by: Philippe Mathieu-Daudé >> --- >> FIXME: reword with something that makes more sense... >> --- >> block/nvme.c | 6 ++++-- >> 1 file changed, 4 insertions(+), 2 deletions(-) >> >> diff --git a/block/nvme.c b/block/nvme.c >> index 71f8cf27a8..ffda804a8e 100644 >> --- a/block/nvme.c >> +++ b/block/nvme.c >> @@ -438,6 +438,7 @@ static void nvme_identify(BlockDriverState *bs, int namespace, Error **errp) >> BDRVNVMeState *s = bs->opaque; >> NvmeIdCtrl *idctrl; >> NvmeIdNs *idns; >> + size_t idsz_max; >> NvmeLBAF *lbaf; >> uint8_t *resp; >> uint16_t oncs; >> @@ -448,14 +449,15 @@ static void nvme_identify(BlockDriverState *bs, int namespace, Error **errp) >> .cdw10 = cpu_to_le32(0x1), >> }; >> >> - resp = qemu_try_blockalign0(bs, sizeof(NvmeIdCtrl)); >> + idsz_max = MAX_CONST(sizeof(NvmeIdCtrl), sizeof(NvmeIdNs)); >> + resp = qemu_try_blockalign0(bs, idsz_max); >> if (!resp) { >> error_setg(errp, "Cannot allocate buffer for identify response"); >> goto out; >> } >> idctrl = (NvmeIdCtrl *)resp; >> idns = (NvmeIdNs *)resp; >> - r = qemu_vfio_dma_map(s->vfio, resp, sizeof(NvmeIdCtrl), true, &iova); >> + r = qemu_vfio_dma_map(s->vfio, resp, idsz_max, true, &iova); > > _nvme_check_size() has compile-time asserts that check > sizeof(NvmeIdCtrl) == sizeof(NvmeIdNs) == 4096. > > I suggest the following cleanup: > > union { > NvmeIdCtrl ctrl; > NvmeIdNs ns; > } *id; > ... > id = qemu_try_blockalign0(bs, sizeof(*id)); > ... > r = qemu_vfio_dma_map(s->vfio, resp, sizeof(*id), true, &iova); > > and accesses to idctl are replaced with id->ctrl and idns with id->ns. > > This eliminates the casts, makes it clear that this data is overlapping, > and avoids the need for idsz_max. Clever idea, thanks!