Hi Anup, On Mon, Jan 31, 2022 at 1:09 PM Anup Patel <anup@xxxxxxxxxxxxxx> wrote: > On Fri, Jan 28, 2022 at 2:09 PM Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote: > > On Fri, Jan 28, 2022 at 1:13 AM Atish Patra <atishp@xxxxxxxxxxxxxx> wrote: > > > On Thu, Jan 27, 2022 at 12:48 AM Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote: > > >> On Thu, Jan 27, 2022 at 2:02 AM Atish Patra <atishp@xxxxxxxxxxxxxx> wrote: > > >> > On Wed, Jan 26, 2022 at 1:10 AM Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote: > > >> > > On Wed, Jan 26, 2022 at 9:28 AM Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote: > > >> > > > On Wed, Jan 26, 2022 at 3:21 AM Atish Patra <atishp@xxxxxxxxxxxxxx> wrote: > > >> > > > > On Tue, Jan 25, 2022 at 2:26 PM Jessica Clarke <jrtc27@xxxxxxxxxx> wrote: > > >> > > > > > On 20 Jan 2022, at 09:09, Atish Patra <atishp@xxxxxxxxxxxx> wrote: > > >> > > > > > > Currently, SBI APIs accept a hartmask that is generated from struct > > >> > > > > > > cpumask. Cpumask data structure can hold upto NR_CPUs value. Thus, it > > >> > > > > > > is not the correct data structure for hartids as it can be higher > > >> > > > > > > than NR_CPUs for platforms with sparse or discontguous hartids. > > >> > > > > > > > > >> > > > > > > Remove all association between hartid mask and struct cpumask. > > >> > > > > > > > > >> > > > > > > Reviewed-by: Anup Patel <anup@xxxxxxxxxxxxxx> (For Linux RISC-V changes) > > >> > > > > > > Acked-by: Anup Patel <anup@xxxxxxxxxxxxxx> (For KVM RISC-V changes) > > >> > > > > > > Signed-off-by: Atish Patra <atishp@xxxxxxxxxxxx> > > >> > > > > > >> > > > > I am yet to reproduce it on my end. > > >> > > > > @Geert Uytterhoeven: can you please try the below diff on your end. > > >> > > > > > >> > > > Unfortunately it doesn't fix the issue for me. > > >> > > > > > >> > > > /me debugging... > > >> > > > > >> > > Found it: after this commit, the SBI_EXT_RFENCE_REMOTE_FENCE_I and > > >> > > SBI_EXT_RFENCE_REMOTE_SFENCE_VMA ecalls are now called with > > >> > > hmask = 0x8000000000000001 and hbase = 1 instead of hmask = 3 and > > >> > > hbase = 0. > > >> > > > > >> > > cpuid 1 maps to hartid 0 > > >> > > cpuid 0 maps to hartid 1 > > >> > > > > >> > > __sbi_rfence_v02:364: cpuid 1 hartid 0 > > >> > > __sbi_rfence_v02:377: hartid 0 hbase 1 > > >> > > hmask |= 1UL << (hartid - hbase); > > >> > > > > >> > > oops > > >> > > > > >> > > __sbi_rfence_v02_call:303: SBI_EXT_RFENCE_REMOTE_FENCE_I hmask > > >> > > 8000000000000001 hbase 1 > > >> > > > > >> > > > >> > Ahh yes. hmask will be incorrect if the bootcpu(cpu 0) is a higher > > >> > hartid and it is trying to do a remote tlb flush/IPI > > >> > to lower the hartid. We should generate the hartid array before the loop. > > >> > > > >> > Can you try this diff ? It seems to work for me during multiple boot > > >> > cycle on the unleashed. > > >> > > > >> > You can find the patch here as well > > >> > https://github.com/atishp04/linux/commits/v5.17-rc1 > > > > >> > @@ -345,13 +368,21 @@ static int __sbi_rfence_v02(int fid, const > > >> > struct cpumask *cpu_mask, > > >> > unsigned long arg4, unsigned long arg5) > > >> > { > > >> > unsigned long hartid, cpuid, hmask = 0, hbase = 0; > > >> > - int result; > > >> > + int result, index = 0, max_index = 0; > > >> > + unsigned long hartid_arr[NR_CPUS] = {0}; > > >> > > >> That's up to 256 bytes on the stack. And more if the maximum > > >> number of cores is increased. > > >> > > > > > > Yeah. We can switch to dynamic allocation using kmalloc based on > > > the number of bits set in the cpumask. > > > > Even more overhead... > > > > >> > - if (!cpu_mask) > > >> > + if (!cpu_mask || cpumask_empty(cpu_mask)) > > >> > cpu_mask = cpu_online_mask; > > >> > > > >> > for_each_cpu(cpuid, cpu_mask) { > > >> > hartid = cpuid_to_hartid_map(cpuid); > > >> > + hartid_arr[index] = hartid; > > >> > + index++; > > >> > + } > > >> > + max_index = index; > > >> > + sort(hartid_arr, max_index, sizeof(unsigned long), cmp_ulong, NULL); > > >> > + for (index = 0; index < max_index; index++) { > > >> > + hartid = hartid_arr[index]; > > >> > > >> That looks expensive to me. > > >> > > >> What about shifting hmask and adjusting hbase if a hartid is > > >> lower than the current hbase? > > > > > > That will probably work for current systems but it will fail when we have hartid > 64. > > > The below logic as it assumes that the hartids are in order. We can have a situation > > > where a two consecutive cpuid belong to hartids that require two invocations of sbi call > > > because the number of harts exceeds BITS_PER_LONG. > > > > If the number of harts exceeds BITS_PER_LONG, you always need multiple > > calls, right? > > > > I think the below (gmail-whitespace-damaged diff) should work: [...] > > > > Another simpler solution would be to just round hbase down to a > > multiple of 32/64 (gmail-whitespace-damaged diff): [...] > > But that means multiple SBI calls if you have e.g. hartids 1-64. > > The shifted mask solution doesn't suffer from that. > > Both solutions don't sort the CPUs, so they are suboptimal in case of > > hartid numberings like 0, 64, 1, 65, ... > > In most cases, the hartids will be in sorted order under /cpus DT node > but it is not guaranteed that boot_cpu will be having smallest hartid > > This means hartid numbering will be something like: > 0, 1, 2, ....., > 64, 0, 1, 2, .... > 31, 0, 1, 2, ..... > > > > > What do you think? > > Assuming hartids under /cpus DT node are ordered, I think your > approach will only have one additional SBI call compared to Atish's > approach but Atish's approach will require more memory with > increasing NR_CPUS so I suggest we go with your approach. > > Can you send a patch with your approach ? Sure, done. https://lore.kernel.org/r/cover.1643635156.git.geert@xxxxxxxxxxxxxx/ Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
