Hi Bartlomiej,
On 12/20/2018 07:21 PM, Bartlomiej Zolnierkiewicz wrote:
> On 11/26/2018 11:02 AM, Konstantin Khorenko wrote:
>> Scrollback frame buffer is rather big - 32K,
>> so it requires 3rd order page, so let's use kvmalloc() instead of
>> ordinary kmalloc() for it.
>
> Is it actually safe to use non-contiguous memory for softback_buf?
Well, that's why we need a review. :)
i've asked myself same question while fixing this,
i've dig sources a bit and did not find places when softback_buf is provided
for DMA,
all other places seems to work with virtual addresses, so there should be no
problem.
Even more i saw a function which mentions that softback might be non-contigious:
/* As we might be inside of softback, we may work with non-contiguous buffer,
that's why we have to use a separate routine. */
static void fbcon_invert_region(struct vc_data *vc, u16 * p, int cnt)
So i think it's safe to use kvmalloc() here.
--
Best regards,
Konstantin Khorenko,
Virtuozzo Linux Kernel Team
>> Signed-off-by: Konstantin Khorenko
>> ---
>> drivers/video/fbdev/core/fbcon.c | 6 +++---
>> 1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/video/fbdev/core/fbcon.c
>> b/drivers/video/fbdev/core/fbcon.c
>> index 8958ccc8b1ac..2b1a34d3f5e2 100644
>> --- a/drivers/video/fbdev/core/fbcon.c
>> +++ b/drivers/video/fbdev/core/fbcon.c
>> @@ -992,7 +992,7 @@ static const char *fbcon_startup(void)
>> if (!softback_buf) {
>> softback_buf =
>> (unsigned long)
>> -kmalloc(fbcon_softback_size,
>> +kvmalloc(fbcon_softback_size,
>> GFP_KERNEL);
>> if (!softback_buf) {
>> fbcon_softback_size = 0;
>> @@ -1001,7 +1001,7 @@ static const char *fbcon_startup(void)
>> }
>> } else {
>> if (softback_buf) {
>> -kfree((void *) softback_buf);
>> +kvfree((void *) softback_buf);
>> softback_buf = 0;
>> softback_top = 0;
>> }
>> @@ -3665,7 +3665,7 @@ static void fbcon_exit(void)
>> }
>> #endif
>>
>> -kfree((void *)softback_buf);
>> +kvfree((void *)softback_buf);
>> softback_buf = 0UL;
>>
>> for_each_registered_fb(i) {
>
> Best regards,
> --
> Bartlomiej Zolnierkiewicz
> Samsung R&D Institute Poland
> Samsung Electronics
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