On Sat, Sep 26, 2020 at 3:16 PM Damien Le Moal <[email protected]> wrote: > > On Sat, 2020-09-26 at 09:31 +0000, Anup Patel wrote: > > > -----Original Message----- > > > From: Damien Le Moal <[email protected]> > > > Sent: 26 September 2020 14:55 > > > To: [email protected]; [email protected]; > > > [email protected]; Anup Patel <[email protected]>; > > > [email protected] > > > Cc: [email protected]; [email protected]; Atish Patra > > > <[email protected]>; Alistair Francis <[email protected]>; linux- > > > [email protected] > > > Subject: Re: [PATCH] RISC-V: Check clint_time_val before use > > > > > > On Sat, 2020-09-26 at 12:57 +0530, Anup Patel wrote: > > > > The NoMMU kernel is broken for QEMU virt machine from Linux-5.9-rc6 > > > > because the get_cycles() and friends are called very early from > > > > rand_initialize() before CLINT driver is probed. To fix this, we > > > > should check clint_time_val before use in get_cycles() and friends. > > > > > > > > Fixes: d5be89a8d118 ("RISC-V: Resurrect the MMIO timer implementation > > > > for M-mode systems") > > > > Signed-off-by: Anup Patel <[email protected]> > > > > --- > > > > arch/riscv/include/asm/timex.h | 12 +++++++++--- > > > > 1 file changed, 9 insertions(+), 3 deletions(-) > > > > > > > > diff --git a/arch/riscv/include/asm/timex.h > > > > b/arch/riscv/include/asm/timex.h index 7f659dda0032..52b42bb1602c > > > > 100644 > > > > --- a/arch/riscv/include/asm/timex.h > > > > +++ b/arch/riscv/include/asm/timex.h > > > > @@ -17,18 +17,24 @@ typedef unsigned long cycles_t; #ifdef > > > > CONFIG_64BIT static inline cycles_t get_cycles(void) { > > > > - return readq_relaxed(clint_time_val); > > > > + if (clint_time_val) > > > > + return readq_relaxed(clint_time_val); > > > > + return 0; > > > > } > > > > #else /* !CONFIG_64BIT */ > > > > static inline u32 get_cycles(void) > > > > { > > > > - return readl_relaxed(((u32 *)clint_time_val)); > > > > + if (clint_time_val) > > > > + return readl_relaxed(((u32 *)clint_time_val)); > > > > + return 0; > > > > } > > > > #define get_cycles get_cycles > > > > > > > > static inline u32 get_cycles_hi(void) { > > > > - return readl_relaxed(((u32 *)clint_time_val) + 1); > > > > + if (clint_time_val) > > > > + return readl_relaxed(((u32 *)clint_time_val) + 1); > > > > + return 0 > > > > } > > > > #define get_cycles_hi get_cycles_hi > > > > #endif /* CONFIG_64BIT */ > > > > > > Applying this on top of rc6, I now get a hang on Kendryte boot... > > > No problems without the patch on the other hand. > > > > Not sure about the issue with Kendryte but I get a crash on > > QEMU virt machine without this patch. > > With this applied in addition to your patch, it works. > > diff --git a/drivers/clocksource/timer-clint.c b/drivers/clocksource/timer- > clint.c > index d17367dee02c..8dbec85979fd 100644 > --- a/drivers/clocksource/timer-clint.c > +++ b/drivers/clocksource/timer-clint.c > @@ -37,7 +37,7 @@ static unsigned long clint_timer_freq; > static unsigned int clint_timer_irq; > > #ifdef CONFIG_RISCV_M_MODE > -u64 __iomem *clint_time_val; > +u64 __iomem *clint_time_val = NULL; > #endif > > static void clint_send_ipi(const struct cpumask *target)
Ahh, clint_time_val is an uninitialized variable. I will send a v2 with your SoB. Regards, Anup > > -- > Damien Le Moal > Western Digital
