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Message-ID: <CAOnJCUJuOxNZvUQ0-Bg5STr=OzkqaS729RQevmQyfDMXNLG8ag@mail.gmail.com>
Date: Mon, 31 Jan 2022 13:18:20 -0800
From: Atish Patra <atishp@...shpatra.org>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>,
Anup Patel <anup@...infault.org>,
Atish Patra <atishp@...osinc.com>,
Jessica Clarke <jrtc27@...c27.com>,
Emil Renner Berthing <kernel@...il.dk>,
linux-riscv <linux-riscv@...ts.infradead.org>,
"linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] RISC-V: Fix IPI/RFENCE hmask on non-monotonic hartid ordering
On Mon, Jan 31, 2022 at 5:26 AM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
>
> If the boot CPU does not have the lowest hartid, "hartid - hbase" can
> become negative, leading to an incorrect hmask, causing userspace to
> crash with SEGV. This is observed on e.g. Starlight Beta, where cpuid 1
> maps to hartid 0, and cpuid 0 maps to hartid 1.
>
> Fix this by detecting this case, and shifting the accumulated mask and
> updating hbase, if possible.
>
> Fixes: 26fb751ca37846c9 ("RISC-V: Do not use cpumask data structure for hartid bitmap")
> Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> ---
> arch/riscv/kernel/sbi.c | 57 ++++++++++++++++++++++++++++-------------
> 1 file changed, 39 insertions(+), 18 deletions(-)
>
> diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c
> index 22444cfcd56cc646..775d3322b422fe14 100644
> --- a/arch/riscv/kernel/sbi.c
> +++ b/arch/riscv/kernel/sbi.c
> @@ -250,7 +250,7 @@ static void __sbi_set_timer_v02(uint64_t stime_value)
>
> static int __sbi_send_ipi_v02(const struct cpumask *cpu_mask)
> {
> - unsigned long hartid, cpuid, hmask = 0, hbase = 0;
> + unsigned long hartid, cpuid, hmask = 0, hbase = 0, htop = 0;
> struct sbiret ret = {0};
> int result;
>
> @@ -259,16 +259,27 @@ static int __sbi_send_ipi_v02(const struct cpumask *cpu_mask)
>
> for_each_cpu(cpuid, cpu_mask) {
> hartid = cpuid_to_hartid_map(cpuid);
> - if (hmask && ((hbase + BITS_PER_LONG) <= hartid)) {
> - ret = sbi_ecall(SBI_EXT_IPI, SBI_EXT_IPI_SEND_IPI,
> - hmask, hbase, 0, 0, 0, 0);
> - if (ret.error)
> - goto ecall_failed;
> - hmask = 0;
> - hbase = 0;
> + if (hmask) {
> + if (hartid + BITS_PER_LONG <= htop ||
> + hbase + BITS_PER_LONG <= hartid) {
> + ret = sbi_ecall(SBI_EXT_IPI,
> + SBI_EXT_IPI_SEND_IPI, hmask,
> + hbase, 0, 0, 0, 0);
> + if (ret.error)
> + goto ecall_failed;
> + hmask = 0;
> + } else if (hartid < hbase) {
> + /* shift the mask to fit lower hartid */
> + hmask <<= hbase - hartid;
> + hbase = hartid;
> + }
> }
> - if (!hmask)
> + if (!hmask) {
> hbase = hartid;
> + htop = hartid;
> + } else if (hartid > htop) {
> + htop = hartid;
> + }
> hmask |= BIT(hartid - hbase);
> }
>
> @@ -345,7 +356,7 @@ static int __sbi_rfence_v02(int fid, const struct cpumask *cpu_mask,
> unsigned long start, unsigned long size,
> unsigned long arg4, unsigned long arg5)
> {
> - unsigned long hartid, cpuid, hmask = 0, hbase = 0;
> + unsigned long hartid, cpuid, hmask = 0, hbase = 0, htop = 0;
> int result;
>
> if (!cpu_mask || cpumask_empty(cpu_mask))
> @@ -353,16 +364,26 @@ static int __sbi_rfence_v02(int fid, const struct cpumask *cpu_mask,
>
> for_each_cpu(cpuid, cpu_mask) {
> hartid = cpuid_to_hartid_map(cpuid);
> - if (hmask && ((hbase + BITS_PER_LONG) <= hartid)) {
> - result = __sbi_rfence_v02_call(fid, hmask, hbase,
> - start, size, arg4, arg5);
> - if (result)
> - return result;
> - hmask = 0;
> - hbase = 0;
> + if (hmask) {
> + if (hartid + BITS_PER_LONG <= htop ||
> + hbase + BITS_PER_LONG <= hartid) {
> + result = __sbi_rfence_v02_call(fid, hmask,
> + hbase, start, size, arg4, arg5);
> + if (result)
> + return result;
> + hmask = 0;
> + } else if (hartid < hbase) {
> + /* shift the mask to fit lower hartid */
> + hmask <<= hbase - hartid;
> + hbase = hartid;
> + }
> }
> - if (!hmask)
> + if (!hmask) {
> hbase = hartid;
> + htop = hartid;
> + } else if (hartid > htop) {
> + htop = hartid;
> + }
> hmask |= BIT(hartid - hbase);
> }
>
> --
> 2.25.1
>
>
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv
Reviewed-by: Atish Patra <atishp@...osinc.com>
Tested-by: Atish Patra <atishp@...osinc.com>
--
Regards,
Atish
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