From 19b50696f9ff94306c2e8ab6fd077e26193e8af9 Mon Sep 17 00:00:00 2001 From: Taylor Stark Date: Thu, 15 Jul 2021 15:35:05 -0700 Subject: [PATCH 1/2] virtio-pmem: Support PCI BAR-relative addresses Update virtio-pmem to allow for the pmem region to be specified in either guest absolute terms or as a PCI BAR-relative address. This is required to support virtio-pmem in Hyper-V, since Hyper-V only allows PCI devices to operate on PCI memory ranges defined via BARs. Virtio-pmem will check for a shared memory window and use that if found, else it will fallback to using the guest absolute addresses in virtio_pmem_config. This was chosen over defining a new feature bit, since it's similar to how virtio-fs is configured. Signed-off-by: Taylor Stark Link: https://lore.kernel.org/r/20210715223505.GA29329@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net Signed-off-by: Tyler Hicks --- drivers/nvdimm/virtio_pmem.c | 21 +++++++++++++++++---- drivers/nvdimm/virtio_pmem.h | 3 +++ 2 files changed, 20 insertions(+), 4 deletions(-) diff --git a/drivers/nvdimm/virtio_pmem.c b/drivers/nvdimm/virtio_pmem.c index 726c7354d465..43c1d835a449 100644 --- a/drivers/nvdimm/virtio_pmem.c +++ b/drivers/nvdimm/virtio_pmem.c @@ -37,6 +37,8 @@ static int virtio_pmem_probe(struct virtio_device *vdev) struct virtio_pmem *vpmem; struct resource res; int err = 0; + bool have_shm_region; + struct virtio_shm_region pmem_region; if (!vdev->config->get) { dev_err(&vdev->dev, "%s failure: config access disabled\n", @@ -58,10 +60,21 @@ static int virtio_pmem_probe(struct virtio_device *vdev) goto out_err; } - virtio_cread_le(vpmem->vdev, struct virtio_pmem_config, - start, &vpmem->start); - virtio_cread_le(vpmem->vdev, struct virtio_pmem_config, - size, &vpmem->size); + /* Retrieve the pmem device's address and size. It may have been supplied + * as a PCI BAR-relative shared memory region, or as a guest absolute address. + */ + have_shm_region = virtio_get_shm_region(vpmem->vdev, &pmem_region, + VIRTIO_PMEM_SHMCAP_ID_PMEM_REGION); + + if (have_shm_region) { + vpmem->start = pmem_region.addr; + vpmem->size = pmem_region.len; + } else { + virtio_cread_le(vpmem->vdev, struct virtio_pmem_config, + start, &vpmem->start); + virtio_cread_le(vpmem->vdev, struct virtio_pmem_config, + size, &vpmem->size); + } res.start = vpmem->start; res.end = vpmem->start + vpmem->size - 1; diff --git a/drivers/nvdimm/virtio_pmem.h b/drivers/nvdimm/virtio_pmem.h index 0dddefe594c4..62bb564e81cb 100644 --- a/drivers/nvdimm/virtio_pmem.h +++ b/drivers/nvdimm/virtio_pmem.h @@ -50,6 +50,9 @@ struct virtio_pmem { __u64 size; }; +/* For the id field in virtio_pci_shm_cap */ +#define VIRTIO_PMEM_SHMCAP_ID_PMEM_REGION 0 + void virtio_pmem_host_ack(struct virtqueue *vq); int async_pmem_flush(struct nd_region *nd_region, struct bio *bio); #endif From 9194f84de8a58bc1a83125054286d649e35054be Mon Sep 17 00:00:00 2001 From: Taylor Stark Date: Thu, 15 Jul 2021 15:36:38 -0700 Subject: [PATCH 2/2] virtio-pmem: Set DRIVER_OK status prior to creating pmem region Update virtio-pmem to call virtio_device_ready prior to creating the pmem region. Otherwise, the guest may try to access the pmem region prior to the DRIVER_OK status being set. In the case of Hyper-V, the backing pmem file isn't mapped to the guest until the DRIVER_OK status is set. Therefore, attempts to access the pmem region can cause the guest to crash. Hyper-V could map the file earlier, for example at VM creation, but we didn't want to pay the mapping cost if the device is never used. Additionally, it felt weird to allow the guest to access the region prior to the device fully coming online. Signed-off-by: Taylor Stark Reviewed-by: Pankaj Gupta Link: https://lore.kernel.org/r/20210715223638.GA29649@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net Signed-off-by: Tyler Hicks --- drivers/nvdimm/virtio_pmem.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/nvdimm/virtio_pmem.c b/drivers/nvdimm/virtio_pmem.c index 43c1d835a449..ea9e111f3ea1 100644 --- a/drivers/nvdimm/virtio_pmem.c +++ b/drivers/nvdimm/virtio_pmem.c @@ -91,6 +91,11 @@ static int virtio_pmem_probe(struct virtio_device *vdev) dev_set_drvdata(&vdev->dev, vpmem->nvdimm_bus); + /* Online the device prior to creating a pmem region, to ensure that + * the region is never touched while the device is offline. + */ + virtio_device_ready(vdev); + ndr_desc.res = &res; ndr_desc.numa_node = nid; ndr_desc.flush = async_pmem_flush; @@ -105,6 +110,7 @@ static int virtio_pmem_probe(struct virtio_device *vdev) nd_region->provider_data = dev_to_virtio(nd_region->dev.parent->parent); return 0; out_nd: + vdev->config->reset(vdev); nvdimm_bus_unregister(vpmem->nvdimm_bus); out_vq: vdev->config->del_vqs(vdev);