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

Arnd Bergmann
2024-03-18T20:02:44Z

On Mon, Mar 18, 2024, at 20:30, Niklas Cassel wrote:
> diff --git a/drivers/misc/pci_endpoint_test.c b/drivers/misc/pci_endpoint_test.c
> index 705029ad8eb5..cb6c9ccf3a5f 100644
> --- a/drivers/misc/pci_endpoint_test.c
> +++ b/drivers/misc/pci_endpoint_test.c
> @@ -272,31 +272,59 @@ 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);
> +
> + /* Make sure that reads are performed after writes. */
> + mb();
> + memcpy_fromio(read_buf, test->bar[barno] + offset, size);

Did you see actual bugs without the barrier? On normal PCI
semantics, a read will always force a write to be flushed first.

Arnd