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Date: Sat, 26 Sep 2020 09:31:57 +0000 From: Anup Patel <Anup.Patel@....com> To: Damien Le Moal <Damien.LeMoal@....com>, "paul.walmsley@...ive.com" <paul.walmsley@...ive.com>, "palmer@...belt.com" <palmer@...belt.com>, "palmerdabbelt@...gle.com" <palmerdabbelt@...gle.com>, "aou@...s.berkeley.edu" <aou@...s.berkeley.edu> CC: "anup@...infault.org" <anup@...infault.org>, "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>, Atish Patra <Atish.Patra@....com>, Alistair Francis <Alistair.Francis@....com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> Subject: RE: [PATCH] RISC-V: Check clint_time_val before use > -----Original Message----- > From: Damien Le Moal <Damien.LeMoal@....com> > Sent: 26 September 2020 14:55 > To: paul.walmsley@...ive.com; palmer@...belt.com; > palmerdabbelt@...gle.com; Anup Patel <Anup.Patel@....com>; > aou@...s.berkeley.edu > Cc: anup@...infault.org; linux-riscv@...ts.infradead.org; Atish Patra > <Atish.Patra@....com>; Alistair Francis <Alistair.Francis@....com>; linux- > kernel@...r.kernel.org > 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 <anup.patel@....com> > > --- > > 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. Regards, Anup
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