linux-kernel - Re: [PATCH] cxl/mem: Fix memory device capacity probing

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Date:   Sat, 17 Apr 2021 00:54:27 +0000
From:   "Verma, Vishal L" <vishal.l.verma@...el.com>
To:     "Williams, Dan J" <dan.j.williams@...el.com>,
        "linux-cxl@...r.kernel.org" <linux-cxl@...r.kernel.org>
CC:     "Widawsky, Ben" <ben.widawsky@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cxl/mem: Fix memory device capacity probing

On Fri, 2021-04-16 at 17:43 -0700, Dan Williams wrote:
> The CXL Identify Memory Device output payload emits capacity in 256MB
> units. The driver is treating the capacity field as bytes. This was
> missed because QEMU reports bytes when it should report bytes / 256MB.
> 
> Fixes: 8adaf747c9f0 ("cxl/mem: Find device capabilities")
> Cc: Ben Widawsky <ben.widawsky@...el.com>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> ---
>  drivers/cxl/mem.c |    7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)

Looks good,
Reviewed-by: Vishal Verma <vishal.l.verma@...el.com>

> 
> diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
> index 1b5078311f7d..2acc6173da36 100644
> --- a/drivers/cxl/mem.c
> +++ b/drivers/cxl/mem.c
> @@ -4,6 +4,7 @@
>  #include <linux/security.h>
>  #include <linux/debugfs.h>
>  #include <linux/module.h>
> +#include <linux/sizes.h>
>  #include <linux/mutex.h>
>  #include <linux/cdev.h>
>  #include <linux/idr.h>
> @@ -1419,6 +1420,7 @@ static int cxl_mem_enumerate_cmds(struct cxl_mem *cxlm)
>   */
>  static int cxl_mem_identify(struct cxl_mem *cxlm)
>  {
> +	/* See CXL 2.0 Table 175 Identify Memory Device Output Payload */
>  	struct cxl_mbox_identify {
>  		char fw_revision[0x10];
>  		__le64 total_capacity;
> @@ -1447,10 +1449,11 @@ static int cxl_mem_identify(struct cxl_mem *cxlm)
>  	 * For now, only the capacity is exported in sysfs
>  	 */
>  	cxlm->ram_range.start = 0;
> -	cxlm->ram_range.end = le64_to_cpu(id.volatile_capacity) - 1;
> +	cxlm->ram_range.end = le64_to_cpu(id.volatile_capacity) * SZ_256M - 1;
>  
> 
> 
> 
>  	cxlm->pmem_range.start = 0;
> -	cxlm->pmem_range.end = le64_to_cpu(id.persistent_capacity) - 1;
> +	cxlm->pmem_range.end =
> +		le64_to_cpu(id.persistent_capacity) * SZ_256M - 1;
>  
> 
> 
> 
>  	memcpy(cxlm->firmware_version, id.fw_revision, sizeof(id.fw_revision));
>  
> 
> 
> 
>