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Fri, 18 Dec 2020 16:40:50 +0000 (GMT) Received: from oc3016276355.ibm.com (unknown [9.145.46.39]) by d06av25.portsmouth.uk.ibm.com (Postfix) with ESMTP; Fri, 18 Dec 2020 16:40:50 +0000 (GMT) Subject: Re: [PATCH v2 2/2] s390x/pci: Fix memory_region_access_valid call To: Cornelia Huck References: <1608243397-29428-1-git-send-email-mjrosato@linux.ibm.com> <1608243397-29428-3-git-send-email-mjrosato@linux.ibm.com> <72f4e03f-7208-6af0-4cd2-9715d9f9ec77@linux.ibm.com> <20201218120440.36b56e80.cohuck@redhat.com> <2c5a2ccb-dbe1-f355-3980-462be1d93942@linux.ibm.com> <20201218163206.7b8efa2a.cohuck@redhat.com> From: Pierre Morel Message-ID: <52c93c12-b9a4-99ba-186c-4db2e6267b9f@linux.ibm.com> Date: Fri, 18 Dec 2020 17:40:50 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: <20201218163206.7b8efa2a.cohuck@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.343, 18.0.737 definitions=2020-12-18_10:2020-12-18, 2020-12-18 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 bulkscore=0 priorityscore=1501 suspectscore=0 phishscore=0 adultscore=0 mlxlogscore=999 impostorscore=0 lowpriorityscore=0 clxscore=1015 mlxscore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2012180111 Received-SPF: pass client-ip=148.163.158.5; envelope-from=pmorel@linux.ibm.com; helo=mx0a-001b2d01.pphosted.com X-Spam_score_int: -26 X-Spam_score: -2.7 X-Spam_bar: -- X-Spam_report: (-2.7 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no 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: thuth@redhat.com, Matthew Rosato , david@redhat.com, richard.henderson@linaro.org, qemu-devel@nongnu.org, pasic@linux.ibm.com, borntraeger@de.ibm.com, qemu-s390x@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 12/18/20 4:32 PM, Cornelia Huck wrote: > On Fri, 18 Dec 2020 15:32:08 +0100 > Pierre Morel wrote: > >> On 12/18/20 12:04 PM, Cornelia Huck wrote: >>> On Fri, 18 Dec 2020 10:37:38 +0100 >>> Pierre Morel wrote: >>> >>>> On 12/17/20 11:16 PM, Matthew Rosato wrote: >>>>> In pcistb_service_handler, a call is made to validate that the memory >>>>> region can be accessed. However, the call is made using the entire length >>>>> of the pcistb operation, which can be larger than the allowed memory >>>>> access size (8). Since we already know that the provided buffer is a >>>>> multiple of 8, fix the call to memory_region_access_valid to iterate >>>>> over the memory region in the same way as the subsequent call to >>>>> memory_region_dispatch_write. >>>>> >>>>> Fixes: 863f6f52b7 ("s390: implement pci instructions") >>>>> Signed-off-by: Matthew Rosato >>>>> --- >>>>> hw/s390x/s390-pci-inst.c | 10 ++++++---- >>>>> 1 file changed, 6 insertions(+), 4 deletions(-) >>>>> >>>>> diff --git a/hw/s390x/s390-pci-inst.c b/hw/s390x/s390-pci-inst.c >>>>> index e230293..76b08a3 100644 >>>>> --- a/hw/s390x/s390-pci-inst.c >>>>> +++ b/hw/s390x/s390-pci-inst.c >>>>> @@ -821,10 +821,12 @@ int pcistb_service_call(S390CPU *cpu, uint8_t r1, uint8_t r3, uint64_t gaddr, >>>>> mr = s390_get_subregion(mr, offset, len); >>>>> offset -= mr->addr; >>>>> >>>>> - if (!memory_region_access_valid(mr, offset, len, true, >>>>> - MEMTXATTRS_UNSPECIFIED)) { >>>>> - s390_program_interrupt(env, PGM_OPERAND, ra); >>>>> - return 0; >>>>> + for (i = 0; i < len; i += 8) { >>>>> + if (!memory_region_access_valid(mr, offset + i, 8, true, >>>>> + MEMTXATTRS_UNSPECIFIED)) { >>>>> + s390_program_interrupt(env, PGM_OPERAND, ra); >>>>> + return 0; >>>>> + } >>>>> } >>>>> >>>>> if (s390_cpu_virt_mem_read(cpu, gaddr, ar, buffer, len)) { >>>>> >>>> >>>> wouldn't it be made automatically by defining the io_region >>>> max_access_size when reading the bars in clp_service_call? >>>> >>> >>> But that's already what is happening, isn't it? The access check is >>> done for a size that is potentially too large, while the actual access >>> will happen in chunks of 8? I think that this patch is correct. >>> >> >> Sorry I was too rapid and half wrong in my writing I was also not >> specific enough. >> >> In MemoryRegionOps we have a field valid with a callback accepts(). >> >> I was wondering if doing the check in the accept() callback which is >> called by the memory_region_access_valid() function and then using >> max_access_size would not be cleaner. >> >> Note that it does not change a lot but only where the check is done. > > But where would we add those ops? My understanding is that pcistb acts > on whatever region the device provided, and that differs from device to > device? > > The ops already exist, I thought adding a dedicated callback for s390 on every regions used by vfio_pci instead of the default. But it does not add a lot, just looks cleaner to me. -- Pierre Morel IBM Lab Boeblingen