| Message ID | 20210918160221.111902-1-alex@ghiti.fr (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | riscv: Flush current cpu icache before other cpus | expand |
(+cc stable) Le 18/09/2021 à 18:02, Alexandre Ghiti a écrit : > On SiFive Unmatched, I recently fell onto the following BUG when booting: > > [ 0.000000] ftrace: allocating 36610 entries in 144 pages > [ 0.000000] Oops - illegal instruction [#1] > [ 0.000000] Modules linked in: > [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 5.13.1+ #5 > [ 0.000000] Hardware name: SiFive HiFive Unmatched A00 (DT) > [ 0.000000] epc : riscv_cpuid_to_hartid_mask+0x6/0xae > [ 0.000000] ra : __sbi_rfence_v02+0xc8/0x10a > [ 0.000000] epc : ffffffff80007240 ra : ffffffff80009964 sp : ffffffff81803e10 > [ 0.000000] gp : ffffffff81a1ea70 tp : ffffffff8180f500 t0 : ffffffe07fe30000 > [ 0.000000] t1 : 0000000000000004 t2 : 0000000000000000 s0 : ffffffff81803e60 > [ 0.000000] s1 : 0000000000000000 a0 : ffffffff81a22238 a1 : ffffffff81803e10 > [ 0.000000] a2 : 0000000000000000 a3 : 0000000000000000 a4 : 0000000000000000 > [ 0.000000] a5 : 0000000000000000 a6 : ffffffff8000989c a7 : 0000000052464e43 > [ 0.000000] s2 : ffffffff81a220c8 s3 : 0000000000000000 s4 : 0000000000000000 > [ 0.000000] s5 : 0000000000000000 s6 : 0000000200000100 s7 : 0000000000000001 > [ 0.000000] s8 : ffffffe07fe04040 s9 : ffffffff81a22c80 s10: 0000000000001000 > [ 0.000000] s11: 0000000000000004 t3 : 0000000000000001 t4 : 0000000000000008 > [ 0.000000] t5 : ffffffcf04000808 t6 : ffffffe3ffddf188 > [ 0.000000] status: 0000000200000100 badaddr: 0000000000000000 cause: 0000000000000002 > [ 0.000000] [<ffffffff80007240>] riscv_cpuid_to_hartid_mask+0x6/0xae > [ 0.000000] [<ffffffff80009474>] sbi_remote_fence_i+0x1e/0x26 > [ 0.000000] [<ffffffff8000b8f4>] flush_icache_all+0x12/0x1a > [ 0.000000] [<ffffffff8000666c>] patch_text_nosync+0x26/0x32 > [ 0.000000] [<ffffffff8000884e>] ftrace_init_nop+0x52/0x8c > [ 0.000000] [<ffffffff800f051e>] ftrace_process_locs.isra.0+0x29c/0x360 > [ 0.000000] [<ffffffff80a0e3c6>] ftrace_init+0x80/0x130 > [ 0.000000] [<ffffffff80a00f8c>] start_kernel+0x5c4/0x8f6 > [ 0.000000] ---[ end trace f67eb9af4d8d492b ]--- > [ 0.000000] Kernel panic - not syncing: Attempted to kill the idle task! > [ 0.000000] ---[ end Kernel panic - not syncing: Attempted to kill the idle task! ]--- > > While ftrace is looping over a list of addresses to patch, it always failed > when patching the same function: riscv_cpuid_to_hartid_mask. Looking at the > backtrace, the illegal instruction is encountered in this same function. > However, patch_text_nosync, after patching the instructions, calls > flush_icache_range. But looking at what happens in this function: > > flush_icache_range -> flush_icache_all > -> sbi_remote_fence_i > -> __sbi_rfence_v02 > -> riscv_cpuid_to_hartid_mask > > The icache and dcache of the current cpu are never synchronized between the > patching of riscv_cpuid_to_hartid_mask and calling this same function. > > So fix this by flushing the current cpu's icache before asking for the other > cpus to do the same. > > Signed-off-by: Alexandre Ghiti <alex@ghiti.fr> > --- > arch/riscv/mm/cacheflush.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c > index 094118663285..89f81067e09e 100644 > --- a/arch/riscv/mm/cacheflush.c > +++ b/arch/riscv/mm/cacheflush.c > @@ -16,6 +16,8 @@ static void ipi_remote_fence_i(void *info) > > void flush_icache_all(void) > { > + local_flush_icache_all(); > + > if (IS_ENABLED(CONFIG_RISCV_SBI)) > sbi_remote_fence_i(NULL); > else >
On Sat, Sep 18, 2021 at 06:05:09PM +0200, Alex Ghiti wrote: > (+cc stable) > <formletter> This is not the correct way to submit patches for inclusion in the stable kernel tree. Please read: https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html for how to do this properly. </formletter>
On Sat, Sep 18, 2021 at 9:03 AM Alexandre Ghiti <alex@ghiti.fr> wrote: > > On SiFive Unmatched, I recently fell onto the following BUG when booting: > > [ 0.000000] ftrace: allocating 36610 entries in 144 pages > [ 0.000000] Oops - illegal instruction [#1] > [ 0.000000] Modules linked in: > [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 5.13.1+ #5 > [ 0.000000] Hardware name: SiFive HiFive Unmatched A00 (DT) > [ 0.000000] epc : riscv_cpuid_to_hartid_mask+0x6/0xae > [ 0.000000] ra : __sbi_rfence_v02+0xc8/0x10a > [ 0.000000] epc : ffffffff80007240 ra : ffffffff80009964 sp : ffffffff81803e10 > [ 0.000000] gp : ffffffff81a1ea70 tp : ffffffff8180f500 t0 : ffffffe07fe30000 > [ 0.000000] t1 : 0000000000000004 t2 : 0000000000000000 s0 : ffffffff81803e60 > [ 0.000000] s1 : 0000000000000000 a0 : ffffffff81a22238 a1 : ffffffff81803e10 > [ 0.000000] a2 : 0000000000000000 a3 : 0000000000000000 a4 : 0000000000000000 > [ 0.000000] a5 : 0000000000000000 a6 : ffffffff8000989c a7 : 0000000052464e43 > [ 0.000000] s2 : ffffffff81a220c8 s3 : 0000000000000000 s4 : 0000000000000000 > [ 0.000000] s5 : 0000000000000000 s6 : 0000000200000100 s7 : 0000000000000001 > [ 0.000000] s8 : ffffffe07fe04040 s9 : ffffffff81a22c80 s10: 0000000000001000 > [ 0.000000] s11: 0000000000000004 t3 : 0000000000000001 t4 : 0000000000000008 > [ 0.000000] t5 : ffffffcf04000808 t6 : ffffffe3ffddf188 > [ 0.000000] status: 0000000200000100 badaddr: 0000000000000000 cause: 0000000000000002 > [ 0.000000] [<ffffffff80007240>] riscv_cpuid_to_hartid_mask+0x6/0xae > [ 0.000000] [<ffffffff80009474>] sbi_remote_fence_i+0x1e/0x26 > [ 0.000000] [<ffffffff8000b8f4>] flush_icache_all+0x12/0x1a > [ 0.000000] [<ffffffff8000666c>] patch_text_nosync+0x26/0x32 > [ 0.000000] [<ffffffff8000884e>] ftrace_init_nop+0x52/0x8c > [ 0.000000] [<ffffffff800f051e>] ftrace_process_locs.isra.0+0x29c/0x360 > [ 0.000000] [<ffffffff80a0e3c6>] ftrace_init+0x80/0x130 > [ 0.000000] [<ffffffff80a00f8c>] start_kernel+0x5c4/0x8f6 > [ 0.000000] ---[ end trace f67eb9af4d8d492b ]--- > [ 0.000000] Kernel panic - not syncing: Attempted to kill the idle task! > [ 0.000000] ---[ end Kernel panic - not syncing: Attempted to kill the idle task! ]--- > > While ftrace is looping over a list of addresses to patch, it always failed > when patching the same function: riscv_cpuid_to_hartid_mask. Looking at the > backtrace, the illegal instruction is encountered in this same function. > However, patch_text_nosync, after patching the instructions, calls > flush_icache_range. But looking at what happens in this function: > > flush_icache_range -> flush_icache_all > -> sbi_remote_fence_i > -> __sbi_rfence_v02 > -> riscv_cpuid_to_hartid_mask > > The icache and dcache of the current cpu are never synchronized between the > patching of riscv_cpuid_to_hartid_mask and calling this same function. > > So fix this by flushing the current cpu's icache before asking for the other > cpus to do the same. > Is this the same bugs described in this thread ? http://lkml.iu.edu/hypermail/linux/kernel/2108.1/05465.html > Signed-off-by: Alexandre Ghiti <alex@ghiti.fr> > --- > arch/riscv/mm/cacheflush.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c > index 094118663285..89f81067e09e 100644 > --- a/arch/riscv/mm/cacheflush.c > +++ b/arch/riscv/mm/cacheflush.c > @@ -16,6 +16,8 @@ static void ipi_remote_fence_i(void *info) > > void flush_icache_all(void) > { > + local_flush_icache_all(); > + > if (IS_ENABLED(CONFIG_RISCV_SBI)) > sbi_remote_fence_i(NULL); > else > -- > 2.30.2 > > > _______________________________________________ > linux-riscv mailing list > linux-riscv@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-riscv
Hi Atish, On 9/19/21 4:35 AM, Atish Patra wrote: > On Sat, Sep 18, 2021 at 9:03 AM Alexandre Ghiti <alex@ghiti.fr> wrote: >> On SiFive Unmatched, I recently fell onto the following BUG when booting: >> >> [ 0.000000] ftrace: allocating 36610 entries in 144 pages >> [ 0.000000] Oops - illegal instruction [#1] >> [ 0.000000] Modules linked in: >> [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 5.13.1+ #5 >> [ 0.000000] Hardware name: SiFive HiFive Unmatched A00 (DT) >> [ 0.000000] epc : riscv_cpuid_to_hartid_mask+0x6/0xae >> [ 0.000000] ra : __sbi_rfence_v02+0xc8/0x10a >> [ 0.000000] epc : ffffffff80007240 ra : ffffffff80009964 sp : ffffffff81803e10 >> [ 0.000000] gp : ffffffff81a1ea70 tp : ffffffff8180f500 t0 : ffffffe07fe30000 >> [ 0.000000] t1 : 0000000000000004 t2 : 0000000000000000 s0 : ffffffff81803e60 >> [ 0.000000] s1 : 0000000000000000 a0 : ffffffff81a22238 a1 : ffffffff81803e10 >> [ 0.000000] a2 : 0000000000000000 a3 : 0000000000000000 a4 : 0000000000000000 >> [ 0.000000] a5 : 0000000000000000 a6 : ffffffff8000989c a7 : 0000000052464e43 >> [ 0.000000] s2 : ffffffff81a220c8 s3 : 0000000000000000 s4 : 0000000000000000 >> [ 0.000000] s5 : 0000000000000000 s6 : 0000000200000100 s7 : 0000000000000001 >> [ 0.000000] s8 : ffffffe07fe04040 s9 : ffffffff81a22c80 s10: 0000000000001000 >> [ 0.000000] s11: 0000000000000004 t3 : 0000000000000001 t4 : 0000000000000008 >> [ 0.000000] t5 : ffffffcf04000808 t6 : ffffffe3ffddf188 >> [ 0.000000] status: 0000000200000100 badaddr: 0000000000000000 cause: 0000000000000002 >> [ 0.000000] [<ffffffff80007240>] riscv_cpuid_to_hartid_mask+0x6/0xae >> [ 0.000000] [<ffffffff80009474>] sbi_remote_fence_i+0x1e/0x26 >> [ 0.000000] [<ffffffff8000b8f4>] flush_icache_all+0x12/0x1a >> [ 0.000000] [<ffffffff8000666c>] patch_text_nosync+0x26/0x32 >> [ 0.000000] [<ffffffff8000884e>] ftrace_init_nop+0x52/0x8c >> [ 0.000000] [<ffffffff800f051e>] ftrace_process_locs.isra.0+0x29c/0x360 >> [ 0.000000] [<ffffffff80a0e3c6>] ftrace_init+0x80/0x130 >> [ 0.000000] [<ffffffff80a00f8c>] start_kernel+0x5c4/0x8f6 >> [ 0.000000] ---[ end trace f67eb9af4d8d492b ]--- >> [ 0.000000] Kernel panic - not syncing: Attempted to kill the idle task! >> [ 0.000000] ---[ end Kernel panic - not syncing: Attempted to kill the idle task! ]--- >> >> While ftrace is looping over a list of addresses to patch, it always failed >> when patching the same function: riscv_cpuid_to_hartid_mask. Looking at the >> backtrace, the illegal instruction is encountered in this same function. >> However, patch_text_nosync, after patching the instructions, calls >> flush_icache_range. But looking at what happens in this function: >> >> flush_icache_range -> flush_icache_all >> -> sbi_remote_fence_i >> -> __sbi_rfence_v02 >> -> riscv_cpuid_to_hartid_mask >> >> The icache and dcache of the current cpu are never synchronized between the >> patching of riscv_cpuid_to_hartid_mask and calling this same function. >> >> So fix this by flushing the current cpu's icache before asking for the other >> cpus to do the same. >> > Is this the same bugs described in this thread ? > > http://lkml.iu.edu/hypermail/linux/kernel/2108.1/05465.html My issue can be explained this way: This is what objdump output looks like in my case: ffffffff8000723a <riscv_cpuid_to_hartid_mask>: ffffffff8000723a: 0001 nop ffffffff8000723c: 0001 nop ffffffff8000723e: 0001 nop ffffffff80007240: 0001 nop ffffffff80007242: 0001 nop ffffffff80007244: 0001 nop ffffffff80007246: 0001 nop ffffffff80007248: 0001 nop This will get patched to: ffffffff8000723a <riscv_cpuid_to_hartid_mask>: ffffffff8000723a: 0013 ffffffff8000723c: 0000 nop ffffffff8000723e: 0013 ffffffff80007240: 0000 nop ffffffff80007242: 0013 ffffffff80007244: 0000 nop ffffffff80007246: 0013 ffffffff80007248: 0000 nop But 0xffffffff80007240 is the beginning of a new cache line, so actually for some reason, the following will be in icache: ffffffff8000723a <riscv_cpuid_to_hartid_mask>: ffffffff8000723a: 0001 nop ffffffff8000723c: 0001 nop ffffffff8000723e: 0001 nop ffffffff80007240: 0000 unimp <- new cache line ffffffff80007242: 0013 ffffffff80007244: 0000 nop ffffffff80007246: 0013 ffffffff80007248: 0000 nop 0x0001 at 0xffffffff8000723e is executed as a nop but then 0x0000 is an invalid instruction, hence the trap. Regarding Dimitri issue, given the address where it traps, the code objdumped would look like: ffffffff80007200: 0001 nop ffffffff80007202: 0001 nop ffffffff80007204: 0001 nop ffffffff80007206: 0001 nop ffffffff80007208: 0001 nop ffffffff8000720a: 0001 nop ffffffff8000720c: 0001 nop ffffffff8000720e: 0001 nop Once patched it looks like: ffffffff80007200: 0013 nop ffffffff80007202: 0000 ffffffff80007204: 0013 nop ffffffff80007206: 0000 ffffffff80007208: 0013 nop ffffffff8000720a: 0000 ffffffff8000720c: 0013 nop ffffffff8000720e: 0000 So if we imagine that until 0xffffffff8000720c, the code that is executed is the first unpatched version and then at 0xffffffff8000720e, the cache line gets reloaded, that can explain the illegal instruction. But it's a bit far-fetched. Actually I don't understand how the whole thing can work, because between the moment the code is patched and other harts are asked to sync their caches, there's a large window where what I explained above can happen right? Alex > >> Signed-off-by: Alexandre Ghiti <alex@ghiti.fr> >> --- >> arch/riscv/mm/cacheflush.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c >> index 094118663285..89f81067e09e 100644 >> --- a/arch/riscv/mm/cacheflush.c >> +++ b/arch/riscv/mm/cacheflush.c >> @@ -16,6 +16,8 @@ static void ipi_remote_fence_i(void *info) >> >> void flush_icache_all(void) >> { >> + local_flush_icache_all(); >> + >> if (IS_ENABLED(CONFIG_RISCV_SBI)) >> sbi_remote_fence_i(NULL); >> else >> -- >> 2.30.2 >> >> >> _______________________________________________ >> linux-riscv mailing list >> linux-riscv@lists.infradead.org >> http://lists.infradead.org/mailman/listinfo/linux-riscv > >
On Sat, 18 Sep 2021 09:02:21 PDT (-0700), alex@ghiti.fr wrote: > On SiFive Unmatched, I recently fell onto the following BUG when booting: > > [ 0.000000] ftrace: allocating 36610 entries in 144 pages > [ 0.000000] Oops - illegal instruction [#1] > [ 0.000000] Modules linked in: > [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 5.13.1+ #5 > [ 0.000000] Hardware name: SiFive HiFive Unmatched A00 (DT) > [ 0.000000] epc : riscv_cpuid_to_hartid_mask+0x6/0xae > [ 0.000000] ra : __sbi_rfence_v02+0xc8/0x10a > [ 0.000000] epc : ffffffff80007240 ra : ffffffff80009964 sp : ffffffff81803e10 > [ 0.000000] gp : ffffffff81a1ea70 tp : ffffffff8180f500 t0 : ffffffe07fe30000 > [ 0.000000] t1 : 0000000000000004 t2 : 0000000000000000 s0 : ffffffff81803e60 > [ 0.000000] s1 : 0000000000000000 a0 : ffffffff81a22238 a1 : ffffffff81803e10 > [ 0.000000] a2 : 0000000000000000 a3 : 0000000000000000 a4 : 0000000000000000 > [ 0.000000] a5 : 0000000000000000 a6 : ffffffff8000989c a7 : 0000000052464e43 > [ 0.000000] s2 : ffffffff81a220c8 s3 : 0000000000000000 s4 : 0000000000000000 > [ 0.000000] s5 : 0000000000000000 s6 : 0000000200000100 s7 : 0000000000000001 > [ 0.000000] s8 : ffffffe07fe04040 s9 : ffffffff81a22c80 s10: 0000000000001000 > [ 0.000000] s11: 0000000000000004 t3 : 0000000000000001 t4 : 0000000000000008 > [ 0.000000] t5 : ffffffcf04000808 t6 : ffffffe3ffddf188 > [ 0.000000] status: 0000000200000100 badaddr: 0000000000000000 cause: 0000000000000002 > [ 0.000000] [<ffffffff80007240>] riscv_cpuid_to_hartid_mask+0x6/0xae > [ 0.000000] [<ffffffff80009474>] sbi_remote_fence_i+0x1e/0x26 > [ 0.000000] [<ffffffff8000b8f4>] flush_icache_all+0x12/0x1a > [ 0.000000] [<ffffffff8000666c>] patch_text_nosync+0x26/0x32 > [ 0.000000] [<ffffffff8000884e>] ftrace_init_nop+0x52/0x8c > [ 0.000000] [<ffffffff800f051e>] ftrace_process_locs.isra.0+0x29c/0x360 > [ 0.000000] [<ffffffff80a0e3c6>] ftrace_init+0x80/0x130 > [ 0.000000] [<ffffffff80a00f8c>] start_kernel+0x5c4/0x8f6 > [ 0.000000] ---[ end trace f67eb9af4d8d492b ]--- > [ 0.000000] Kernel panic - not syncing: Attempted to kill the idle task! > [ 0.000000] ---[ end Kernel panic - not syncing: Attempted to kill the idle task! ]--- > > While ftrace is looping over a list of addresses to patch, it always failed > when patching the same function: riscv_cpuid_to_hartid_mask. Looking at the > backtrace, the illegal instruction is encountered in this same function. > However, patch_text_nosync, after patching the instructions, calls > flush_icache_range. But looking at what happens in this function: > > flush_icache_range -> flush_icache_all > -> sbi_remote_fence_i > -> __sbi_rfence_v02 > -> riscv_cpuid_to_hartid_mask > > The icache and dcache of the current cpu are never synchronized between the > patching of riscv_cpuid_to_hartid_mask and calling this same function. > > So fix this by flushing the current cpu's icache before asking for the other > cpus to do the same. > > Signed-off-by: Alexandre Ghiti <alex@ghiti.fr> > --- > arch/riscv/mm/cacheflush.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c > index 094118663285..89f81067e09e 100644 > --- a/arch/riscv/mm/cacheflush.c > +++ b/arch/riscv/mm/cacheflush.c > @@ -16,6 +16,8 @@ static void ipi_remote_fence_i(void *info) > > void flush_icache_all(void) > { > + local_flush_icache_all(); > + > if (IS_ENABLED(CONFIG_RISCV_SBI)) > sbi_remote_fence_i(NULL); > else Thanks, this is on fixes (with the tags for stable)
diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c index 094118663285..89f81067e09e 100644 --- a/arch/riscv/mm/cacheflush.c +++ b/arch/riscv/mm/cacheflush.c @@ -16,6 +16,8 @@ static void ipi_remote_fence_i(void *info) void flush_icache_all(void) { + local_flush_icache_all(); + if (IS_ENABLED(CONFIG_RISCV_SBI)) sbi_remote_fence_i(NULL); else
On SiFive Unmatched, I recently fell onto the following BUG when booting: [ 0.000000] ftrace: allocating 36610 entries in 144 pages [ 0.000000] Oops - illegal instruction [#1] [ 0.000000] Modules linked in: [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 5.13.1+ #5 [ 0.000000] Hardware name: SiFive HiFive Unmatched A00 (DT) [ 0.000000] epc : riscv_cpuid_to_hartid_mask+0x6/0xae [ 0.000000] ra : __sbi_rfence_v02+0xc8/0x10a [ 0.000000] epc : ffffffff80007240 ra : ffffffff80009964 sp : ffffffff81803e10 [ 0.000000] gp : ffffffff81a1ea70 tp : ffffffff8180f500 t0 : ffffffe07fe30000 [ 0.000000] t1 : 0000000000000004 t2 : 0000000000000000 s0 : ffffffff81803e60 [ 0.000000] s1 : 0000000000000000 a0 : ffffffff81a22238 a1 : ffffffff81803e10 [ 0.000000] a2 : 0000000000000000 a3 : 0000000000000000 a4 : 0000000000000000 [ 0.000000] a5 : 0000000000000000 a6 : ffffffff8000989c a7 : 0000000052464e43 [ 0.000000] s2 : ffffffff81a220c8 s3 : 0000000000000000 s4 : 0000000000000000 [ 0.000000] s5 : 0000000000000000 s6 : 0000000200000100 s7 : 0000000000000001 [ 0.000000] s8 : ffffffe07fe04040 s9 : ffffffff81a22c80 s10: 0000000000001000 [ 0.000000] s11: 0000000000000004 t3 : 0000000000000001 t4 : 0000000000000008 [ 0.000000] t5 : ffffffcf04000808 t6 : ffffffe3ffddf188 [ 0.000000] status: 0000000200000100 badaddr: 0000000000000000 cause: 0000000000000002 [ 0.000000] [<ffffffff80007240>] riscv_cpuid_to_hartid_mask+0x6/0xae [ 0.000000] [<ffffffff80009474>] sbi_remote_fence_i+0x1e/0x26 [ 0.000000] [<ffffffff8000b8f4>] flush_icache_all+0x12/0x1a [ 0.000000] [<ffffffff8000666c>] patch_text_nosync+0x26/0x32 [ 0.000000] [<ffffffff8000884e>] ftrace_init_nop+0x52/0x8c [ 0.000000] [<ffffffff800f051e>] ftrace_process_locs.isra.0+0x29c/0x360 [ 0.000000] [<ffffffff80a0e3c6>] ftrace_init+0x80/0x130 [ 0.000000] [<ffffffff80a00f8c>] start_kernel+0x5c4/0x8f6 [ 0.000000] ---[ end trace f67eb9af4d8d492b ]--- [ 0.000000] Kernel panic - not syncing: Attempted to kill the idle task! [ 0.000000] ---[ end Kernel panic - not syncing: Attempted to kill the idle task! ]--- While ftrace is looping over a list of addresses to patch, it always failed when patching the same function: riscv_cpuid_to_hartid_mask. Looking at the backtrace, the illegal instruction is encountered in this same function. However, patch_text_nosync, after patching the instructions, calls flush_icache_range. But looking at what happens in this function: flush_icache_range -> flush_icache_all -> sbi_remote_fence_i -> __sbi_rfence_v02 -> riscv_cpuid_to_hartid_mask The icache and dcache of the current cpu are never synchronized between the patching of riscv_cpuid_to_hartid_mask and calling this same function. So fix this by flushing the current cpu's icache before asking for the other cpus to do the same. Signed-off-by: Alexandre Ghiti <alex@ghiti.fr> --- arch/riscv/mm/cacheflush.c | 2 ++ 1 file changed, 2 insertions(+)