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

[Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>]

Hi,

On 3/20/24 2:01 AM, 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);

Why 1MB  limit?

>  
> -	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;
>  	}
>  
> -	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)

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer