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Date: Wed, 29 May 2024 09:43:42 -0700
From: Alison Schofield <alison.schofield@intel.com>
To: Ilpo =?iso-8859-1?Q?J=E4rvinen?= <ilpo.jarvinen@linux.intel.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>,
	Jonathan Cameron <jonathan.cameron@huawei.com>,
	Dave Jiang <dave.jiang@intel.com>,
	Vishal Verma <vishal.l.verma@intel.com>,
	Ira Weiny <ira.weiny@intel.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Ben Widawsky <bwidawsk@kernel.org>, linux-cxl@vger.kernel.org,
	LKML <linux-kernel@vger.kernel.org>, stable@vger.kernel.org
Subject: Re: [PATCH 1/1] cxl/pci: Convert PCIBIOS_* return codes to errnos
Message-ID: <ZldbPhzJ1LID096X@aschofie-mobl2>
References: <20240527123403.13098-1-ilpo.jarvinen@linux.intel.com>
 <ZlZYrsPfzAiFzNLM@aschofie-mobl2>
 <78e5690b-832f-3da5-3500-141e9b155c09@linux.intel.com>
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In-Reply-To: <78e5690b-832f-3da5-3500-141e9b155c09@linux.intel.com>

On Wed, May 29, 2024 at 03:19:19PM +0300, Ilpo J?rvinen wrote:
> On Tue, 28 May 2024, Alison Schofield wrote:
> 
> > On Mon, May 27, 2024 at 03:34:02PM +0300, Ilpo J?rvinen wrote:
> > > pci_{read,write}_config_*word() and pcie_capability_read_word() return
> > > PCIBIOS_* codes, not usual errnos.
> > > 
> > > Fix return value checks to handle PCIBIOS_* return codes correctly by
> > > dropping < 0 from the check and convert the PCIBIOS_* return codes into
> > > errnos using pcibios_err_to_errno() before returning them.
> > 
> > 
> > Do we ever make a bad decision based on the wrong rc value or is this
> > a correction to the emitted dev_*() messaging, or both?
> 
> There is potential for bad decision.
> 
> Eg. cxl_set_mem_enable() it can return 0, 1 and rc that is currently 
> returning PCIBIOS_* return codes that are > 0).  devm_cxl_enable_mem() 
> then tries to check for >0 and <0 but the <0 condition won't match 
> correctly because PCIBIOS_* is not <0 but >0, devm_cxl_enable_mem() then 
> return 0 where it should have returned an error.
> 
> The positive "error code" from wait_for_valid(), cxl_dvsec_rr_decode(), 
> and cxl_pci_ras_unmask leaks out of .probe().
> 

Ah, I see the fix is quite tidy but the impact is more complex. Please
update the commit log to explain user visible impacts of this fix.


> -- 
>  i.
> 
> > > Fixes: ce17ad0d5498 ("cxl: Wait Memory_Info_Valid before access memory related info")
> > > Fixes: 34e37b4c432c ("cxl/port: Enable HDM Capability after validating DVSEC Ranges")
> > > Fixes: 14d788740774 ("cxl/mem: Consolidate CXL DVSEC Range enumeration in the core")
> > > Fixes: 560f78559006 ("cxl/pci: Retrieve CXL DVSEC memory info")
> > > Cc: stable@vger.kernel.org
> > > Signed-off-by: Ilpo J?rvinen <ilpo.jarvinen@linux.intel.com>
> > > ---
> > >  drivers/cxl/core/pci.c | 30 +++++++++++++++---------------
> > >  drivers/cxl/pci.c      |  2 +-
> > >  2 files changed, 16 insertions(+), 16 deletions(-)
> > > 
> > > diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
> > > index 8567dd11eaac..9ca67d4e0a89 100644
> > > --- a/drivers/cxl/core/pci.c
> > > +++ b/drivers/cxl/core/pci.c
> > > @@ -121,7 +121,7 @@ static int cxl_dvsec_mem_range_valid(struct cxl_dev_state *cxlds, int id)
> > >  					   d + CXL_DVSEC_RANGE_SIZE_LOW(id),
> > >  					   &temp);
> > >  		if (rc)
> > > -			return rc;
> > > +			return pcibios_err_to_errno(rc);
> > >  
> > >  		valid = FIELD_GET(CXL_DVSEC_MEM_INFO_VALID, temp);
> > >  		if (valid)
> > > @@ -155,7 +155,7 @@ static int cxl_dvsec_mem_range_active(struct cxl_dev_state *cxlds, int id)
> > >  		rc = pci_read_config_dword(
> > >  			pdev, d + CXL_DVSEC_RANGE_SIZE_LOW(id), &temp);
> > >  		if (rc)
> > > -			return rc;
> > > +			return pcibios_err_to_errno(rc);
> > >  
> > >  		active = FIELD_GET(CXL_DVSEC_MEM_ACTIVE, temp);
> > >  		if (active)
> > > @@ -188,7 +188,7 @@ int cxl_await_media_ready(struct cxl_dev_state *cxlds)
> > >  	rc = pci_read_config_word(pdev,
> > >  				  d + CXL_DVSEC_CAP_OFFSET, &cap);
> > >  	if (rc)
> > > -		return rc;
> > > +		return pcibios_err_to_errno(rc);
> > >  
> > >  	hdm_count = FIELD_GET(CXL_DVSEC_HDM_COUNT_MASK, cap);
> > >  	for (i = 0; i < hdm_count; i++) {
> > > @@ -225,7 +225,7 @@ static int wait_for_valid(struct pci_dev *pdev, int d)
> > >  	 */
> > >  	rc = pci_read_config_dword(pdev, d + CXL_DVSEC_RANGE_SIZE_LOW(0), &val);
> > >  	if (rc)
> > > -		return rc;
> > > +		return pcibios_err_to_errno(rc);
> > >  
> > >  	if (val & CXL_DVSEC_MEM_INFO_VALID)
> > >  		return 0;
> > > @@ -234,7 +234,7 @@ static int wait_for_valid(struct pci_dev *pdev, int d)
> > >  
> > >  	rc = pci_read_config_dword(pdev, d + CXL_DVSEC_RANGE_SIZE_LOW(0), &val);
> > >  	if (rc)
> > > -		return rc;
> > > +		return pcibios_err_to_errno(rc);
> > >  
> > >  	if (val & CXL_DVSEC_MEM_INFO_VALID)
> > >  		return 0;
> > > @@ -250,8 +250,8 @@ static int cxl_set_mem_enable(struct cxl_dev_state *cxlds, u16 val)
> > >  	int rc;
> > >  
> > >  	rc = pci_read_config_word(pdev, d + CXL_DVSEC_CTRL_OFFSET, &ctrl);
> > > -	if (rc < 0)
> > > -		return rc;
> > > +	if (rc)
> > > +		return pcibios_err_to_errno(rc);
> > >  
> > >  	if ((ctrl & CXL_DVSEC_MEM_ENABLE) == val)
> > >  		return 1;
> > > @@ -259,8 +259,8 @@ static int cxl_set_mem_enable(struct cxl_dev_state *cxlds, u16 val)
> > >  	ctrl |= val;
> > >  
> > >  	rc = pci_write_config_word(pdev, d + CXL_DVSEC_CTRL_OFFSET, ctrl);
> > > -	if (rc < 0)
> > > -		return rc;
> > > +	if (rc)
> > > +		return pcibios_err_to_errno(rc);
> > >  
> > >  	return 0;
> > >  }
> > > @@ -336,11 +336,11 @@ int cxl_dvsec_rr_decode(struct device *dev, int d,
> > >  
> > >  	rc = pci_read_config_word(pdev, d + CXL_DVSEC_CAP_OFFSET, &cap);
> > >  	if (rc)
> > > -		return rc;
> > > +		return pcibios_err_to_errno(rc);
> > >  
> > >  	rc = pci_read_config_word(pdev, d + CXL_DVSEC_CTRL_OFFSET, &ctrl);
> > >  	if (rc)
> > > -		return rc;
> > > +		return pcibios_err_to_errno(rc);
> > >  
> > >  	if (!(cap & CXL_DVSEC_MEM_CAPABLE)) {
> > >  		dev_dbg(dev, "Not MEM Capable\n");
> > > @@ -379,14 +379,14 @@ int cxl_dvsec_rr_decode(struct device *dev, int d,
> > >  		rc = pci_read_config_dword(
> > >  			pdev, d + CXL_DVSEC_RANGE_SIZE_HIGH(i), &temp);
> > >  		if (rc)
> > > -			return rc;
> > > +			return pcibios_err_to_errno(rc);
> > >  
> > >  		size = (u64)temp << 32;
> > >  
> > >  		rc = pci_read_config_dword(
> > >  			pdev, d + CXL_DVSEC_RANGE_SIZE_LOW(i), &temp);
> > >  		if (rc)
> > > -			return rc;
> > > +			return pcibios_err_to_errno(rc);
> > >  
> > >  		size |= temp & CXL_DVSEC_MEM_SIZE_LOW_MASK;
> > >  		if (!size) {
> > > @@ -400,14 +400,14 @@ int cxl_dvsec_rr_decode(struct device *dev, int d,
> > >  		rc = pci_read_config_dword(
> > >  			pdev, d + CXL_DVSEC_RANGE_BASE_HIGH(i), &temp);
> > >  		if (rc)
> > > -			return rc;
> > > +			return pcibios_err_to_errno(rc);
> > >  
> > >  		base = (u64)temp << 32;
> > >  
> > >  		rc = pci_read_config_dword(
> > >  			pdev, d + CXL_DVSEC_RANGE_BASE_LOW(i), &temp);
> > >  		if (rc)
> > > -			return rc;
> > > +			return pcibios_err_to_errno(rc);
> > >  
> > >  		base |= temp & CXL_DVSEC_MEM_BASE_LOW_MASK;
> > >  
> > > diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
> > > index e53646e9f2fb..0ec9cbc64896 100644
> > > --- a/drivers/cxl/pci.c
> > > +++ b/drivers/cxl/pci.c
> > > @@ -540,7 +540,7 @@ static int cxl_pci_ras_unmask(struct pci_dev *pdev)
> > >  
> > >  	rc = pcie_capability_read_word(pdev, PCI_EXP_DEVCTL, &cap);
> > >  	if (rc)
> > > -		return rc;
> > > +		return pcibios_err_to_errno(rc);
> > >  
> > >  	if (cap & PCI_EXP_DEVCTL_URRE) {
> > >  		addr = cxlds->regs.ras + CXL_RAS_UNCORRECTABLE_MASK_OFFSET;
> > > -- 
> > > 2.39.2
> > > 
> >