[PATCH v3 6/6] RISC-V: Do not use cpumask data structure for hartid bitmap

[Ron Economos]

On 1/26/22 17:01, Atish Patra wrote:
> On Wed, Jan 26, 2022 at 1:10 AM Geert Uytterhoeven <geert at linux-m68k.org> wrote:
>> Hi Atish,
>>
>> On Wed, Jan 26, 2022 at 9:28 AM Geert Uytterhoeven <geert at linux-m68k.org> wrote:
>>> On Wed, Jan 26, 2022 at 3:21 AM Atish Patra <atishp at atishpatra.org> wrote:
>>>> On Tue, Jan 25, 2022 at 2:26 PM Jessica Clarke <jrtc27 at jrtc27.com> wrote:
>>>>> On 20 Jan 2022, at 09:09, Atish Patra <atishp at rivosinc.com> 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 at brainfault.org> (For Linux RISC-V changes)
>>>>>> Acked-by: Anup Patel <anup at brainfault.org> (For KVM RISC-V changes)
>>>>>> Signed-off-by: Atish Patra <atishp at rivosinc.com>
>>>> 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
>
> --------------------------------------------------------------------------------------------------------------------------------
> diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c
> index f72527fcb347..4ebeb5813edc 100644
> --- a/arch/riscv/kernel/sbi.c
> +++ b/arch/riscv/kernel/sbi.c
> @@ -8,6 +8,8 @@
>   #include <linux/init.h>
>   #include <linux/pm.h>
>   #include <linux/reboot.h>
> +#include <linux/sort.h>
> +
>   #include <asm/sbi.h>
>   #include <asm/smp.h>
>
> @@ -85,7 +87,7 @@ static unsigned long
> __sbi_v01_cpumask_to_hartmask(const struct cpumask *cpu_mas
>    pr_warn("Unable to send any request to hartid > BITS_PER_LONG for
> SBI v0.1\n");
>    break;
>    }
> - hmask |= 1 << hartid;
> + hmask |= 1UL << hartid;
>    }
>
>    return hmask;
> @@ -160,7 +162,7 @@ static int __sbi_send_ipi_v01(const struct cpumask
> *cpu_mask)
>   {
>    unsigned long hart_mask;
>
> - if (!cpu_mask)
> + if (!cpu_mask || cpumask_empty(cpu_mask))
>    cpu_mask = cpu_online_mask;
>    hart_mask = __sbi_v01_cpumask_to_hartmask(cpu_mask);
>
> @@ -176,7 +178,7 @@ static int __sbi_rfence_v01(int fid, const struct
> cpumask *cpu_mask,
>    int result = 0;
>    unsigned long hart_mask;
>
> - if (!cpu_mask)
> + if (!cpu_mask || cpumask_empty(cpu_mask))
>    cpu_mask = cpu_online_mask;
>    hart_mask = __sbi_v01_cpumask_to_hartmask(cpu_mask);
>
> @@ -236,6 +238,18 @@ static int __sbi_rfence_v01(int fid, const struct
> cpumask *cpu_mask,
>   static void sbi_set_power_off(void) {}
>   #endif /* CONFIG_RISCV_SBI_V01 */
>
> +static int cmp_ulong(const void *A, const void *B)
> +{
> + const unsigned long *a = A, *b = B;
> +
> + if (*a < *b)
> + return -1;
> + else if (*a > *b)
> + return 1;
> + else
> + return 0;
> +}
> +
>   static void __sbi_set_timer_v02(uint64_t stime_value)
>   {
>   #if __riscv_xlen == 32
> @@ -251,13 +265,22 @@ static int __sbi_send_ipi_v02(const struct
> cpumask *cpu_mask)
>   {
>    unsigned long hartid, cpuid, hmask = 0, hbase = 0;
>    struct sbiret ret = {0};
> - int result;
> + int result, index = 0, max_index = 0;
> + unsigned long hartid_arr[NR_CPUS] = {0};
>
> - 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];
>    if (hmask && ((hbase + BITS_PER_LONG) <= hartid)) {
>    ret = sbi_ecall(SBI_EXT_IPI, SBI_EXT_IPI_SEND_IPI,
>    hmask, hbase, 0, 0, 0, 0);
> @@ -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};
>
> - 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];
>    if (hmask && ((hbase + BITS_PER_LONG) <= hartid)) {
>    result = __sbi_rfence_v02_call(fid, hmask, hbase,
>           start, size, arg4, arg5);
>
> --------------------------------------------------------------------------------------------------------------------------------

Works good here. No systemd segfaults on Unmatched.

Tested-by: Ron Economos <re at w6rz.net>