On 7/22/20 2:15 AM, frank.chang@sifive.com wrote:
> -static void vext_clear(void *tail, uint32_t cnt, uint32_t tot)
> +static void vext_clear(void *tail, uint32_t vta, uint32_t cnt, uint32_t tot)
> {
> + if (vta == 0) {
> + /* tail element undisturbed */
> + return;
> + }
> +
> /*
> + * Tail element agnostic.
> * Split the remaining range to two parts.
> * The first part is in the last uint64_t unit.
> * The second part start from the next uint64_t unit.
> @@ -152,41 +168,50 @@ static void vext_clear(void *tail, uint32_t cnt, uint32_t tot)
> if (cnt % 8) {
> part1 = 8 - (cnt % 8);
> part2 = tot - cnt - part1;
> - memset((void *)((uintptr_t)tail & ~(7ULL)), 0, part1);
> - memset((void *)(((uintptr_t)tail + 8) & ~(7ULL)), 0, part2);
> + memset((void *)((uintptr_t)tail & ~(7ULL)), 1, part1);
> + memset((void *)(((uintptr_t)tail + 8) & ~(7ULL)), 1, part2);
> } else {
> - memset(tail, 0, part2);
> + memset(tail, 1, part2);
> }
> }
"1s" surely means all bits set to 1, not each byte to 1.
You're correct, I can't just simply replace the value from 0 to 1.
Is there any reason to do anything with VTA/VMA at all? One alternative for
"agnostic" is to leave the values undisturbed. So the quickest thing for qemu
to do is remove all of this code. Then we don't have to pass the values in
translate either.
Which is exactly what is recommended in the 4th paragraph of the notes
following the VTA/VMA description.
I was trying to keep these codes as an option for the user to specify the behaviors of VTA.
But as long as it's easier for QEMU to just treat VTA/VMA as agnostic(no changes)/undisturbed.
I will remove all the clean functions in my next patchset.
r~
Frank Chang