Re: [PATCH v3] misc: pci_endpoint_test: Use memcpy_toio()/memcpy_fromio() for BAR tests

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

On Fri, Mar 22, 2024 at 11:29:10AM +0100, Niklas Cassel wrote:
> Hello Mani,
> 
> On Fri, Mar 22, 2024 at 03:50:58PM +0530, Manivannan Sadhasivam wrote:
> > On Wed, Mar 20, 2024 at 10:01:05AM +0100, Niklas Cassel wrote:
> > > The current code uses writel()/readl(), which has an implicit memory
> > > barrier for every single readl()/writel().
> > > 
> > > Additionally, reading 4 bytes at a time over the PCI bus is not really
> > > optimal, considering that this code is running in an ioctl handler.
> > > 
> > > Use memcpy_toio()/memcpy_fromio() for BAR tests.
> > > 
> > > Before patch with a 4MB BAR:
> > > $ time /usr/bin/pcitest -b 1
> > > BAR1:           OKAY
> > > real    0m 1.56s
> > > 
> > > After patch with a 4MB BAR:
> > > $ time /usr/bin/pcitest -b 1
> > > BAR1:           OKAY
> > > real    0m 0.54s
> > > 
> > > Signed-off-by: Niklas Cassel <cassel@kernel.org>
> > > ---
> > > Changes since v2:
> > > -Actually free the allocated memory... (thank you Kuppuswamy)
> > > 
> > >  drivers/misc/pci_endpoint_test.c | 68 ++++++++++++++++++++++++++------
> > >  1 file changed, 55 insertions(+), 13 deletions(-)
> > > 
> > > diff --git a/drivers/misc/pci_endpoint_test.c b/drivers/misc/pci_endpoint_test.c
> > > index 705029ad8eb5..1d361589fb61 100644
> > > --- a/drivers/misc/pci_endpoint_test.c
> > > +++ b/drivers/misc/pci_endpoint_test.c
> > > @@ -272,33 +272,75 @@ static const u32 bar_test_pattern[] = {
> > >  	0xA5A5A5A5,
> > >  };
> > >  
> > > +static int pci_endpoint_test_bar_memcmp(struct pci_endpoint_test *test,
> > > +					enum pci_barno barno, int offset,
> > > +					void *write_buf, void *read_buf,
> > > +					int size)
> > > +{
> > > +	memset(write_buf, bar_test_pattern[barno], size);
> > > +	memcpy_toio(test->bar[barno] + offset, write_buf, size);
> > > +
> > > +	memcpy_fromio(read_buf, test->bar[barno] + offset, size);
> > > +
> > > +	return memcmp(write_buf, read_buf, size);
> > > +}
> > > +
> > >  static bool pci_endpoint_test_bar(struct pci_endpoint_test *test,
> > >  				  enum pci_barno barno)
> > >  {
> > > -	int j;
> > > -	u32 val;
> > > -	int size;
> > > +	int j, bar_size, buf_size, iters, remain;
> > > +	void *write_buf;
> > > +	void *read_buf;
> > >  	struct pci_dev *pdev = test->pdev;
> > > +	bool ret;
> > >  
> > >  	if (!test->bar[barno])
> > >  		return false;
> > >  
> > > -	size = pci_resource_len(pdev, barno);
> > > +	bar_size = pci_resource_len(pdev, barno);
> > >  
> > >  	if (barno == test->test_reg_bar)
> > > -		size = 0x4;
> > > +		bar_size = 0x4;
> > >  
> > > -	for (j = 0; j < size; j += 4)
> > > -		pci_endpoint_test_bar_writel(test, barno, j,
> > > -					     bar_test_pattern[barno]);
> > > +	buf_size = min(SZ_1M, bar_size);
> > >  
> > > -	for (j = 0; j < size; j += 4) {
> > > -		val = pci_endpoint_test_bar_readl(test, barno, j);
> > > -		if (val != bar_test_pattern[barno])
> > > -			return false;
> > > +	write_buf = kmalloc(buf_size, GFP_KERNEL);
> > > +	if (!write_buf)
> > > +		return false;
> > > +
> > > +	read_buf = kmalloc(buf_size, GFP_KERNEL);
> > > +	if (!read_buf) {
> > > +		ret = false;
> > > +		goto err;
> > 
> > This frees read_buf also. Please fix that and also rename the labels to:
> > 
> > err_free_write_buf
> > err_free_read_buf
> 
> This was intentional since kfree() handles NULL perfectly fine.
> (I was thinking that it would just add extra lines for no good reason.)
> 
> Do you think that there is any point in having two labels in this case?
> 

I know that NULL is ignored, but that's not an excuse to call kfree() for
non-existent memory (for code sanity). Please create separate labels.

- Mani

> 
> Kind regards,
> Niklas
> 
> > 
> > - Mani
> > 
> > >  	}
> > >  
> > > -	return true;
> > > +	iters = bar_size / buf_size;
> > > +	for (j = 0; j < iters; j++) {
> > > +		if (pci_endpoint_test_bar_memcmp(test, barno, buf_size * j,
> > > +						 write_buf, read_buf,
> > > +						 buf_size)) {
> > > +			ret = false;
> > > +			goto err;
> > > +		}
> > > +	}
> > > +
> > > +	remain = bar_size % buf_size;
> > > +	if (remain) {
> > > +		if (pci_endpoint_test_bar_memcmp(test, barno, buf_size * iters,
> > > +						 write_buf, read_buf,
> > > +						 remain)) {
> > > +			ret = false;
> > > +			goto err;
> > > +		}
> > > +	}
> > > +
> > > +	ret = true;
> > > +
> > > +err:
> > > +	kfree(write_buf);
> > > +	kfree(read_buf);
> > > +
> > > +	return ret;
> > >  }
> > >  
> > >  static bool pci_endpoint_test_intx_irq(struct pci_endpoint_test *test)
> > > -- 
> > > 2.44.0
> > > 
> > 
> > -- 
> > மணிவண்ணன் சதாசிவம்

-- 
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