Re: [PATCH v3 07/17] IB/core: Add flags for on demand paging support

Yann Droneaud
2014-12-16T12:13:52Z

Le mardi 16 décembre 2014 à 13:02 +0100, Yann Droneaud a écrit :
> Le jeudi 11 décembre 2014 à 17:04 +0200, Haggai Eran a écrit :
> > From: Sagi Grimberg <sagig-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
> >
> > * Add a configuration option for enable on-demand paging support in the
> > infiniband subsystem (CONFIG_INFINIBAND_ON_DEMAND_PAGING). In a later patch,
> > this configuration option will select the MMU_NOTIFIER configuration option
> > to enable mmu notifiers.
> > * Add a flag for on demand paging (ODP) support in the IB device capabilities.
> > * Add a flag to request ODP MR in the access flags to reg_mr.
> > * Fail registrations done with the ODP flag when the low-level driver doesn't
> > support this.
> > * Change the conditions in which an MR will be writable to explicitly
> > specify the access flags. This is to avoid making an MR writable just
> > because it is an ODP MR.
> > * Add a ODP capabilities to the extended query device verb.
> >
> > Signed-off-by: Sagi Grimberg <sagig-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
> > Signed-off-by: Shachar Raindel <raindel-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
> > Signed-off-by: Haggai Eran <haggaie-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
> > ---
> > drivers/infiniband/Kconfig | 10 ++++++++++
> > drivers/infiniband/core/umem.c | 8 +++++---
> > drivers/infiniband/core/uverbs_cmd.c | 25 +++++++++++++++++++++++++
> > include/rdma/ib_verbs.h | 28 ++++++++++++++++++++++++++--
> > include/uapi/rdma/ib_user_verbs.h | 15 +++++++++++++++
> > 5 files changed, 81 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/infiniband/Kconfig b/drivers/infiniband/Kconfig
> > index 77089399359b..089a2c2af329 100644
> > --- a/drivers/infiniband/Kconfig
> > +++ b/drivers/infiniband/Kconfig
> > @@ -38,6 +38,16 @@ config INFINIBAND_USER_MEM
> > depends on INFINIBAND_USER_ACCESS != n
> > default y
> >
> > +config INFINIBAND_ON_DEMAND_PAGING
> > + bool "InfiniBand on-demand paging support"
> > + depends on INFINIBAND_USER_MEM
> > + default y
> > + ---help---
> > + On demand paging support for the InfiniBand subsystem.
> > + Together with driver support this allows registration of
> > + memory regions without pinning their pages, fetching the
> > + pages on demand instead.
> > +
> > config INFINIBAND_ADDR_TRANS
> > bool
> > depends on INFINIBAND
> > diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c
> > index 6f152628e0d2..c328e4693d14 100644
> > --- a/drivers/infiniband/core/umem.c
> > +++ b/drivers/infiniband/core/umem.c
> > @@ -107,13 +107,15 @@ struct ib_umem *ib_umem_get(struct ib_ucontext *context, unsigned long addr,
> > umem->page_size = PAGE_SIZE;
> > umem->pid = get_task_pid(current, PIDTYPE_PID);
> > /*
> > - * We ask for writable memory if any access flags other than
> > - * "remote read" are set. "Local write" and "remote write"
> > + * We ask for writable memory if any of the following
> > + * access flags are set. "Local write" and "remote write"
> > * obviously require write access. "Remote atomic" can do
> > * things like fetch and add, which will modify memory, and
> > * "MW bind" can change permissions by binding a window.
> > */
> > - umem->writable = !!(access & ~IB_ACCESS_REMOTE_READ);
> > + umem->writable = !!(access &
> > + (IB_ACCESS_LOCAL_WRITE | IB_ACCESS_REMOTE_WRITE |
> > + IB_ACCESS_REMOTE_ATOMIC | IB_ACCESS_MW_BIND));
> >
> > /* We assume the memory is from hugetlb until proved otherwise */
> > umem->hugetlb = 1;
> > diff --git a/drivers/infiniband/core/uverbs_cmd.c b/drivers/infiniband/core/uverbs_cmd.c
> > index c7a43624c96b..f9326ccda4b5 100644
> > --- a/drivers/infiniband/core/uverbs_cmd.c
> > +++ b/drivers/infiniband/core/uverbs_cmd.c
> > @@ -953,6 +953,18 @@ ssize_t ib_uverbs_reg_mr(struct ib_uverbs_file *file,
> > goto err_free;
> > }
> >
> > + if (cmd.access_flags & IB_ACCESS_ON_DEMAND) {
> > + struct ib_device_attr attr;
> > +
> > + ret = ib_query_device(pd->device, &attr);
> > + if (ret || !(attr.device_cap_flags &
> > + IB_DEVICE_ON_DEMAND_PAGING)) {
> > + pr_debug("ODP support not available\n");
> > + ret = -EINVAL;
> > + goto err_put;
> > + }
> > + }
> > +
> > mr = pd->device->reg_user_mr(pd, cmd.start, cmd.length, cmd.hca_va,
> > cmd.access_flags, &udata);
> > if (IS_ERR(mr)) {
> > @@ -3289,6 +3301,19 @@ int ib_uverbs_ex_query_device(struct ib_uverbs_file *file,
> > copy_query_dev_fields(file, &resp.base, &attr);
> > resp.comp_mask = 0;
> >
> > +#ifdef CONFIG_INFINIBAND_ON_DEMAND_PAGING
> > + if (cmd.comp_mask & IB_USER_VERBS_EX_QUERY_DEVICE_ODP) {
> > + resp.odp_caps.general_caps = attr.odp_caps.general_caps;
> > + resp.odp_caps.per_transport_caps.rc_odp_caps =
> > + attr.odp_caps.per_transport_caps.rc_odp_caps;
> > + resp.odp_caps.per_transport_caps.uc_odp_caps =
> > + attr.odp_caps.per_transport_caps.uc_odp_caps;
> > + resp.odp_caps.per_transport_caps.ud_odp_caps =
> > + attr.odp_caps.per_transport_caps.ud_odp_caps;
> > + resp.comp_mask |= IB_USER_VERBS_EX_QUERY_DEVICE_ODP;
> > + }
>
> You need to clear the tail of the response otherwise, kernel will leak
> stack content to userspace:
>
> + #else /* !CONFIG_INFINIBAND_ON_DEMAND_PAGING */
> + resp.odp_caps.general_caps = 0;
> + resp.odp_caps.per_transport_caps.rc_odp_caps = 0;
> + resp.odp_caps.per_transport_caps.uc_odp_caps = 0;
> + resp.odp_caps.per_transport_caps.ud_odp_caps = 0;
>
> > +#endif
> > +
>
> + resp.odp_caps.reserved = 0
>

I've missed the memset(&resp, 0, sizeof(resp)); added in
ib_uverbs_ex_query_device() as part of '[PATCH v3 06/17] IB/core: Add
support for extended query device caps'.

Sorry for the noise.

> > err = ib_copy_to_udata(ucore, &resp, sizeof(resp));
> > if (err)
> > return err;
> > diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
> > index 97a999f9e4d8..a41bc5a39ebf 100644
> > --- a/include/rdma/ib_verbs.h
> > +++ b/include/rdma/ib_verbs.h
> > @@ -123,7 +123,8 @@ enum ib_device_cap_flags {
> > IB_DEVICE_MEM_WINDOW_TYPE_2A = (1<<23),
> > IB_DEVICE_MEM_WINDOW_TYPE_2B = (1<<24),
> > IB_DEVICE_MANAGED_FLOW_STEERING = (1<<29),
> > - IB_DEVICE_SIGNATURE_HANDOVER = (1<<30)
> > + IB_DEVICE_SIGNATURE_HANDOVER = (1<<30),
> > + IB_DEVICE_ON_DEMAND_PAGING = (1<<31),
> > };
> >
> > enum ib_signature_prot_cap {
> > @@ -143,6 +144,27 @@ enum ib_atomic_cap {
> > IB_ATOMIC_GLOB
> > };
> >
> > +enum ib_odp_general_cap_bits {
> > + IB_ODP_SUPPORT = 1 << 0,
> > +};
> > +
> > +enum ib_odp_transport_cap_bits {
> > + IB_ODP_SUPPORT_SEND = 1 << 0,
> > + IB_ODP_SUPPORT_RECV = 1 << 1,
> > + IB_ODP_SUPPORT_WRITE = 1 << 2,
> > + IB_ODP_SUPPORT_READ = 1 << 3,
> > + IB_ODP_SUPPORT_ATOMIC = 1 << 4,
> > +};
> > +
> > +struct ib_odp_caps {
> > + uint64_t general_caps;
> > + struct {
> > + uint32_t rc_odp_caps;
> > + uint32_t uc_odp_caps;
> > + uint32_t ud_odp_caps;
> > + } per_transport_caps;
> > +};
> > +
> > struct ib_device_attr {
> > u64 fw_ver;
> > __be64 sys_image_guid;
> > @@ -186,6 +208,7 @@ struct ib_device_attr {
> > u8 local_ca_ack_delay;
> > int sig_prot_cap;
> > int sig_guard_cap;
> > + struct ib_odp_caps odp_caps;
> > };
> >
> > enum ib_mtu {
> > @@ -1073,7 +1096,8 @@ enum ib_access_flags {
> > IB_ACCESS_REMOTE_READ = (1<<2),
> > IB_ACCESS_REMOTE_ATOMIC = (1<<3),
> > IB_ACCESS_MW_BIND = (1<<4),
> > - IB_ZERO_BASED = (1<<5)
> > + IB_ZERO_BASED = (1<<5),
> > + IB_ACCESS_ON_DEMAND = (1<<6),
> > };
> >
> > struct ib_phys_buf {
> > diff --git a/include/uapi/rdma/ib_user_verbs.h b/include/uapi/rdma/ib_user_verbs.h
> > index e8a96071e352..4275b961bf60 100644
> > --- a/include/uapi/rdma/ib_user_verbs.h
> > +++ b/include/uapi/rdma/ib_user_verbs.h
> > @@ -202,15 +202,30 @@ struct ib_uverbs_query_device_resp {
> > __u8 reserved[4];
> > };
> >
> > +enum {
> > + IB_USER_VERBS_EX_QUERY_DEVICE_ODP = 1ULL << 0,
> > +};
> > +
> > struct ib_uverbs_ex_query_device {
> > __u32 comp_mask;
> > __u32 reserved;
> > };
> >
> > +struct ib_uverbs_odp_caps {
> > + __u64 general_caps;
> > + struct {
> > + __u32 rc_odp_caps;
> > + __u32 uc_odp_caps;
> > + __u32 ud_odp_caps;
> > + } per_transport_caps;
> > + __u32 reserved;
> > +};
> > +
> > struct ib_uverbs_ex_query_device_resp {
> > struct ib_uverbs_query_device_resp base;
> > __u32 comp_mask;
> > __u32 reserved;
> > + struct ib_uverbs_odp_caps odp_caps;
> > };
>
> Hopefully, no kernel was released with ib_uverbs_ex_query_device_resp
> without odp_caps (eg. in between '[PATCH v3 06/17] IB/core: Add support
> for extended query device caps' and this one, or
> ib_uverbs_ex_query_device() should have been modified
> to handle shorter ib_uverbs_ex_query_device_resp to accomodate the ABI
> variations.
>

Ouch ! I've seen how this would be handled in '[PATCH v3 06/17] IB/core:
Add support for extended query device caps', and I'm disappointed.

static inline int ib_copy_to_udata(struct ib_udata *udata, void *src,
size_t len)
{
size_t copy_sz;

copy_sz = min_t(size_t, len, udata->outlen);
return copy_to_user(udata->outbuf, src, copy_sz) ? -EFAULT : 0;
}

This is not the correct way of doing this, but I'm going to comment on
this issue on the related patch.

Regards.

--
Yann Droneaud
OPTEYA