Messages in this thread | | | Date | Wed, 7 Dec 2022 19:47:35 -0800 | From | Alison Schofield <> | Subject | Re: [PATCH v3 2/6] cxl/mbox: Add GET_POISON_LIST mailbox command |
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On Wed, Dec 07, 2022 at 01:39:58PM -0800, Dan Williams wrote: > Alison Schofield wrote: > > On Tue, Dec 06, 2022 at 06:41:34PM -0800, Dan Williams wrote: > > > alison.schofield@ wrote: > [..] > > > > +int cxl_mem_get_poison(struct cxl_memdev *cxlmd, u64 offset, u64 len, > > > > + struct cxl_region *cxlr) > > > > +{ > > > > + struct cxl_dev_state *cxlds = cxlmd->cxlds; > > > > + const char *memdev_name = dev_name(&cxlmd->dev); > > > > + const char *pcidev_name = dev_name(cxlds->dev); > > > > + struct cxl_mbox_poison_payload_out *po; > > > > + struct cxl_mbox_poison_payload_in pi; > > > > + int nr_records = 0; > > > > + int rc; > > > > + > > > > + po = kvmalloc(cxlds->payload_size, GFP_KERNEL); > > > > + if (!po) > > > > + return -ENOMEM; > > > > + > > > > + pi.offset = cpu_to_le64(offset); > > > > + pi.length = cpu_to_le64(len); > > > > + > > > > + rc = mutex_lock_interruptible(&cxlds->poison_list_mutex); > > > > > > So I do not know what this mutex is protecting if there is an allocation > > > per cxl_mem_get_poison() invocation. Although I suspect that's somewhat > > > wasteful. Just allocate one buffer at the beginning of time and then use > > > the lock to protect that buffer. > > > > Intent was a single lock on the device to protect the state of the > > poison list retrieval - do not allow > 1 reader. With > 1 reader > > software may not know if it retrieved the complete list. > > > > I'm not understanding about protecting a buffer, instead of protecting > > the state. Here I try to protect the state. > > Ah, sorry I read cxlds->poison_list_mutex and assumed it was serializing > access to the buffer, not a state machine. I do think it would be > worthwhile to make this a self contained structure with its own kdoc to > explain what is going on, something like: >
OK thanks, it's getting through to me now. Will do !
> diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h > index ab138004f644..02697d1d951c 100644 > --- a/drivers/cxl/cxlmem.h > +++ b/drivers/cxl/cxlmem.h > @@ -193,6 +193,19 @@ struct cxl_endpoint_dvsec_info { > struct range dvsec_range[2]; > }; > > +/** > + * struct cxl_poison_state - summary > + * @payload: ... > + * @lock: ... > + * > + * A bit more description of why state needs to be held over successive > + * mbox commands... > + */ > +struct cxl_poison_state { > + void *payload; > + struct mutex lock; > +}; > + > /** > * struct cxl_dev_state - The driver device state > * > @@ -210,6 +223,7 @@ struct cxl_endpoint_dvsec_info { > * @lsa_size: Size of Label Storage Area > * (CXL 2.0 8.2.9.5.1.1 Identify Memory Device) > * @mbox_mutex: Mutex to synchronize mailbox access. > + * @poison: Poison list retrieval and tracing > * @firmware_version: Firmware version for the memory device. > * @enabled_cmds: Hardware commands found enabled in CEL. > * @exclusive_cmds: Commands that are kernel-internal only > @@ -244,6 +258,7 @@ struct cxl_dev_state { > size_t payload_size; > size_t lsa_size; > struct mutex mbox_mutex; /* Protects device mailbox and firmware */ > + struct cxl_poison_state poison; > char firmware_version[0x10]; > DECLARE_BITMAP(enabled_cmds, CXL_MEM_COMMAND_ID_MAX); > DECLARE_BITMAP(exclusive_cmds, CXL_MEM_COMMAND_ID_MAX);
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