From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [PATCH 3/7] s390/cio: Split pfn_array_alloc_pin into pieces References: <20190503134912.39756-1-farman@linux.ibm.com> <20190503134912.39756-4-farman@linux.ibm.com> <20190508124327.5c496c8a.cohuck@redhat.com> From: Eric Farman Message-ID: <15e733fc-e6eb-176e-e9bd-3f7629d5f935@linux.ibm.com> Date: Wed, 8 May 2019 09:25:57 -0400 MIME-Version: 1.0 In-Reply-To: <20190508124327.5c496c8a.cohuck@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: kvm-owner@vger.kernel.org List-Archive: List-Post: To: Cornelia Huck Cc: Farhan Ali , Halil Pasic , Pierre Morel , linux-s390@vger.kernel.org, kvm@vger.kernel.org List-ID: On 5/8/19 6:43 AM, Cornelia Huck wrote: > On Fri, 3 May 2019 15:49:08 +0200 > Eric Farman wrote: > >> The pfn_array_alloc_pin routine is doing too much. Today, it does the >> alloc of the pfn_array struct and its member arrays, builds the iova >> address lists out of a contiguous piece of guest memory, and asks vfio >> to pin the resulting pages. >> >> Let's effectively revert a significant portion of commit 5c1cfb1c3948 >> ("vfio: ccw: refactor and improve pfn_array_alloc_pin()") such that we >> break pfn_array_alloc_pin() into its component pieces, and have one >> routine that allocates/populates the pfn_array structs, and another >> that actually pins the memory. In the future, we will be able to >> handle scenarios where pinning memory isn't actually appropriate. >> >> Signed-off-by: Eric Farman >> --- >> drivers/s390/cio/vfio_ccw_cp.c | 72 +++++++++++++++++++++++++++--------------- >> 1 file changed, 47 insertions(+), 25 deletions(-) >> >> diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c >> index f86da78eaeaa..b70306c06150 100644 >> --- a/drivers/s390/cio/vfio_ccw_cp.c >> +++ b/drivers/s390/cio/vfio_ccw_cp.c >> @@ -50,28 +50,25 @@ struct ccwchain { >> }; >> >> /* >> - * pfn_array_alloc_pin() - alloc memory for PFNs, then pin user pages in memory >> + * pfn_array_alloc() - alloc memory for PFNs >> * @pa: pfn_array on which to perform the operation >> - * @mdev: the mediated device to perform pin/unpin operations >> * @iova: target guest physical address >> * @len: number of bytes that should be pinned from @iova >> * >> - * Attempt to allocate memory for PFNs, and pin user pages in memory. >> + * Attempt to allocate memory for PFN. > > s/PFN/PFNs/ > >> * >> * Usage of pfn_array: >> * We expect (pa_nr == 0) and (pa_iova_pfn == NULL), any field in >> * this structure will be filled in by this function. >> * >> * Returns: >> - * Number of pages pinned on success. >> - * If @pa->pa_nr is not 0, or @pa->pa_iova_pfn is not NULL initially, >> - * returns -EINVAL. >> - * If no pages were pinned, returns -errno. >> + * 0 if PFNs are allocated >> + * -EINVAL if pa->pa_nr is not initially zero, or pa->pa_iova_pfn is not NULL >> + * -ENOMEM if alloc failed >> */ >> -static int pfn_array_alloc_pin(struct pfn_array *pa, struct device *mdev, >> - u64 iova, unsigned int len) >> +static int pfn_array_alloc(struct pfn_array *pa, u64 iova, unsigned int len) >> { >> - int i, ret = 0; >> + int i; >> >> if (!len) >> return 0; >> @@ -97,23 +94,33 @@ static int pfn_array_alloc_pin(struct pfn_array *pa, struct device *mdev, >> for (i = 1; i < pa->pa_nr; i++) >> pa->pa_iova_pfn[i] = pa->pa_iova_pfn[i - 1] + 1; >> >> + return 0; >> +} >> + >> +/* >> + * pfn_array_pin() - Pin user pages in memory >> + * @pa: pfn_array on which to perform the operation >> + * @mdev: the mediated device to perform pin operations >> + * >> + * Returns: >> + * Number of pages pinned on success. >> + * If fewer pages than requested were pinned, returns -EINVAL >> + * If no pages were pinned, returns -errno. > > I don't really like the 'returns -errno' :) It's actually the return > code of vfio_pin_pages(), and that might include -EINVAL as well. > > So, what about mentioning in the function description that > pfn_array_pin() only succeeds if it coult pin all pages, and simply > stating that it returns a negative error value on failure? Seems reasonable to me... Something like: * Returns number of pages pinned upon success. * If the pin request partially succeeds, or fails completely, * all pages are left unpinned and a negative error value is returned. > >> + */ >> +static int pfn_array_pin(struct pfn_array *pa, struct device *mdev) >> +{ >> + int ret = 0; >> + >> ret = vfio_pin_pages(mdev, pa->pa_iova_pfn, pa->pa_nr, >> IOMMU_READ | IOMMU_WRITE, pa->pa_pfn); >> >> - if (ret < 0) { >> - goto err_out; >> - } else if (ret > 0 && ret != pa->pa_nr) { >> + if (ret > 0 && ret != pa->pa_nr) { >> vfio_unpin_pages(mdev, pa->pa_iova_pfn, ret); >> ret = -EINVAL; >> - goto err_out; >> } >> >> - return ret; >> - >> -err_out: >> - pa->pa_nr = 0; >> - kfree(pa->pa_iova_pfn); >> - pa->pa_iova_pfn = NULL; >> + if (ret < 0) >> + pa->pa_iova = 0; >> >> return ret; >> } > > (...) >