Re: [PATCH] cxl/events: Use a common struct for DRAM and General Media events

["Fabio M. De Francesco" <fabio.m.de.francesco@linux.intel.com>]

On Thursday, May 16, 2024 11:32:59 PM GMT+2 Ira Weiny wrote:
> Fabio M. De Francesco wrote:
> > Use cxl_event_media as a common structure to record information about DRAM
> > and General Media events because it simplifies handling the two events.
> > 
> > Suggested-by: Dan Williams <dan.j.williams@intel.com>
> > Signed-off-by: Fabio M. De Francesco
> > <fabio.m.de.francesco@linux.intel.com>
> > ---
> > 
> >  drivers/cxl/core/mbox.c      |  6 ++--
> >  drivers/cxl/core/trace.h     |  4 +--
> >  include/linux/cxl-event.h    | 70 +++++++++++++++---------------------
> >  tools/testing/cxl/test/mem.c |  4 +--
> >  4 files changed, 36 insertions(+), 48 deletions(-)
> 
> Other than saving 12 lines of code what are we saving with this change?
>
> The addition of media_common implies an additional event type which is not
> in the specification.  (perhaps confusing future contributors?)  And the
> code is more complex to follow.  The decode of the phys_addr field is not
> simplified (which IIRC was the point of this idea.)
>
> I'm probably being dense but I just don't see the need for the
> struct_group complexity here.
> 
> Ira

Ira,

I think you are right, there is no need for struct_group here and this code is 
unnecessarily complex.

Anyway, for the next version, I'll use the simpler solution showed by Dan in 
his comment on v2.

Thanks,

Fabio
 
> 
> > diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
> > index 2626f3fff201..ad4d7b0f7f4d 100644
> > --- a/drivers/cxl/core/mbox.c
> > +++ b/drivers/cxl/core/mbox.c
> > @@ -875,16 +875,16 @@ void cxl_event_trace_record(const struct cxl_memdev
> > *cxlmd,> 
> >  		guard(rwsem_read)(&cxl_region_rwsem);
> >  		guard(rwsem_read)(&cxl_dpa_rwsem);
> > 
> > -		dpa = le64_to_cpu(evt->common.phys_addr) & 
CXL_DPA_MASK;
> > +		dpa = le64_to_cpu(evt->media_common.phys_addr) & 
CXL_DPA_MASK;
> > 
> >  		cxlr = cxl_dpa_to_region(cxlmd, dpa);
> >  		if (cxlr)
> >  		
> >  			hpa = cxl_trace_hpa(cxlr, cxlmd, dpa);
> >  		
> >  		if (event_type == CXL_CPER_EVENT_GEN_MEDIA)
> >  		
> >  			trace_cxl_general_media(cxlmd, type, cxlr, 
hpa,
> > 
> > -						&evt-
>gen_media);
> > +						&evt-
>media_general);
> > 
> >  		else if (event_type == CXL_CPER_EVENT_DRAM)
> > 
> > -			trace_cxl_dram(cxlmd, type, cxlr, hpa, &evt-
>dram);
> > +			trace_cxl_dram(cxlmd, type, cxlr, hpa, &evt-
>media_dram);
> > 
> >  	}
> >  
> >  }
> >  EXPORT_SYMBOL_NS_GPL(cxl_event_trace_record, CXL);
> > 
> > diff --git a/drivers/cxl/core/trace.h b/drivers/cxl/core/trace.h
> > index 07a0394b1d99..2c7293761bb2 100644
> > --- a/drivers/cxl/core/trace.h
> > +++ b/drivers/cxl/core/trace.h
> > @@ -316,7 +316,7 @@ TRACE_EVENT(cxl_generic_event,
> > 
> >  TRACE_EVENT(cxl_general_media,
> >  
> >  	TP_PROTO(const struct cxl_memdev *cxlmd, enum cxl_event_log_type 
log,
> > 
> > -		 struct cxl_region *cxlr, u64 hpa, struct 
cxl_event_gen_media *rec),
> > +		 struct cxl_region *cxlr, u64 hpa, struct 
cxl_event_media *rec),
> > 
> >  	TP_ARGS(cxlmd, log, cxlr, hpa, rec),
> > 
> > @@ -413,7 +413,7 @@ TRACE_EVENT(cxl_general_media,
> > 
> >  TRACE_EVENT(cxl_dram,
> >  
> >  	TP_PROTO(const struct cxl_memdev *cxlmd, enum cxl_event_log_type 
log,
> > 
> > -		 struct cxl_region *cxlr, u64 hpa, struct 
cxl_event_dram *rec),
> > +		 struct cxl_region *cxlr, u64 hpa, struct 
cxl_event_media *rec),
> > 
> >  	TP_ARGS(cxlmd, log, cxlr, hpa, rec),
> > 
> > diff --git a/include/linux/cxl-event.h b/include/linux/cxl-event.h
> > index 60b25020281f..e417556cc120 100644
> > --- a/include/linux/cxl-event.h
> > +++ b/include/linux/cxl-event.h
> > @@ -32,41 +32,38 @@ struct cxl_event_generic {
> > 
> >   * CXL rev 3.0 Section 8.2.9.2.1.1; Table 8-43
> >   */
> >  
> >  #define CXL_EVENT_GEN_MED_COMP_ID_SIZE	0x10
> > 
> > -struct cxl_event_gen_media {
> > -	struct cxl_event_record_hdr hdr;
> > -	__le64 phys_addr;
> > -	u8 descriptor;
> > -	u8 type;
> > -	u8 transaction_type;
> > -	u8 validity_flags[2];
> > -	u8 channel;
> > -	u8 rank;
> > -	u8 device[3];
> > -	u8 component_id[CXL_EVENT_GEN_MED_COMP_ID_SIZE];
> > -	u8 reserved[46];
> > -} __packed;
> > -
> > 
> >  /*
> >  
> >   * DRAM Event Record - DER
> >   * CXL rev 3.0 section 8.2.9.2.1.2; Table 3-44
> >   */
> >  
> >  #define CXL_EVENT_DER_CORRECTION_MASK_SIZE	0x20
> > 
> > -struct cxl_event_dram {
> > +struct cxl_event_media {
> > 
> >  	struct cxl_event_record_hdr hdr;
> > 
> > -	__le64 phys_addr;
> > -	u8 descriptor;
> > -	u8 type;
> > -	u8 transaction_type;
> > -	u8 validity_flags[2];
> > -	u8 channel;
> > -	u8 rank;
> > -	u8 nibble_mask[3];
> > -	u8 bank_group;
> > -	u8 bank;
> > -	u8 row[3];
> > -	u8 column[2];
> > -	u8 correction_mask[CXL_EVENT_DER_CORRECTION_MASK_SIZE];
> > -	u8 reserved[0x17];
> > +	struct_group_tagged(cxl_event_media_hdr, media_hdr,
> > +		__le64 phys_addr;
> > +		u8 descriptor;
> > +		u8 type;
> > +		u8 transaction_type;
> > +		u8 validity_flags[2];
> > +		u8 channel;
> > +		u8 rank;
> > +	);
> > +	union {
> > +		struct_group(general,
> > +			u8 device[3];
> > +			u8 
component_id[CXL_EVENT_GEN_MED_COMP_ID_SIZE];
> > +			u8 gen_reserved[46];
> > +		);
> > +		struct_group(dram,
> > +			u8 nibble_mask[3];
> > +			u8 bank_group;
> > +			u8 bank;
> > +			u8 row[3];
> > +			u8 column[2];
> > +			u8 
correction_mask[CXL_EVENT_DER_CORRECTION_MASK_SIZE];
> > +			u8 dram_reserved[0x17];
> > +		);
> > +	};
> > 
> >  } __packed;
> >  
> >  /*
> > 
> > @@ -95,21 +92,12 @@ struct cxl_event_mem_module {
> > 
> >  	u8 reserved[0x3d];
> >  
> >  } __packed;
> > 
> > -/*
> > - * General Media or DRAM Event Common Fields
> > - * - provides common access to phys_addr
> > - */
> > -struct cxl_event_common {
> > -	struct cxl_event_record_hdr hdr;
> > -	__le64 phys_addr;
> > -} __packed;
> > -
> > 
> >  union cxl_event {
> >  
> >  	struct cxl_event_generic generic;
> > 
> > -	struct cxl_event_gen_media gen_media;
> > -	struct cxl_event_dram dram;
> > +	struct cxl_event_media media_general;
> > +	struct cxl_event_media media_dram;
> > 
> >  	struct cxl_event_mem_module mem_module;
> > 
> > -	struct cxl_event_common common;
> > +	struct cxl_event_media media_common;
> > 
> >  } __packed;
> >  
> >  /*
> > 
> > diff --git a/tools/testing/cxl/test/mem.c b/tools/testing/cxl/test/mem.c
> > index 6584443144de..0a8fd145c391 100644
> > --- a/tools/testing/cxl/test/mem.c
> > +++ b/tools/testing/cxl/test/mem.c
> > @@ -378,7 +378,7 @@ struct cxl_event_record_raw hardware_replace = {
> > 
> >  struct cxl_test_gen_media {
> >  
> >  	uuid_t id;
> > 
> > -	struct cxl_event_gen_media rec;
> > +	struct cxl_event_media rec;
> > 
> >  } __packed;
> >  
> >  struct cxl_test_gen_media gen_media = {
> > 
> > @@ -402,7 +402,7 @@ struct cxl_test_gen_media gen_media = {
> > 
> >  struct cxl_test_dram {
> >  
> >  	uuid_t id;
> > 
> > -	struct cxl_event_dram rec;
> > +	struct cxl_event_media rec;
> > 
> >  } __packed;
> >  
> >  struct cxl_test_dram dram = {