On 2019-04-17 5:09 p.m., John David Anglin wrote: > On 2019-04-17 5:01 p.m., Helge Deller wrote: >> On 17.04.19 22:58, Helge Deller wrote: >>> On 17.04.19 22:55, Sven Schnelle wrote: >>>> On Fri, Apr 12, 2019 at 07:12:04PM -0400, John David Anglin wrote: >>>>> TLB operations only need to be serialized on machines with the Merced (Stretch) bus. >>>>> The only machines in this category are L and N class, and they require a 64-bit PA 2.0 >>>>> kernel. On these machines, we use local TLB purges in the tmpalias routines. We don't >>>>> need to serialize TLB purges on all other machines. Thus, the lock/unlock code can be >>>>> removed when CONFIG_PA20 is not defined. Further, when CONFIG_PA20 is not defined, >>>>> alternative patching converts the TLB purges to local purges when PA 2.0 hardware has >>>>> been detected. >>>>> >>>>> Signed-off-by: John David Anglin <dave.anglin@xxxxxxxx> >>>> I had this patch running on my C8000 and J5000 for a few days, and haven't >>>> encountered any issues. >>> Nah... >>> I do have one of the critical machines (rp5470), and I tried >>> to add the necessary code to detect and handle the TLB serialization. >>> Until now the patch sadly doesn't work yet (hangs at boot), it still needs more work. >>> You can find it in my git tree: >>> https://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux.git/commit/?h=tlb-flush-merced-bus&id=fc6044f83cb9828ec6ebecb23a46549d9ebc518f >> Please ignore my comments. >> Dave's patch is OK. >> >> I mixed it up with the Mikulas Patocka's patch: "use per-pagetable spinlock" >> https://patchwork.kernel.org/patch/10888249/ > I think this hunk needs fixing to handle merced case: > > diff --git a/arch/parisc/kernel/entry.S b/arch/parisc/kernel/entry.S > index 5796524a3137..3e11fdd9d3af 100644 > --- a/arch/parisc/kernel/entry.S > +++ b/arch/parisc/kernel/entry.S > @@ -48,14 +48,9 @@ > .level 2.0 > #endif > > - .import pa_tlb_lock,data > - .macro load_pa_tlb_lock reg > -#if __PA_LDCW_ALIGNMENT > 4 > - load32 PA(pa_tlb_lock) + __PA_LDCW_ALIGNMENT-1, \reg > - depi 0,31,__PA_LDCW_ALIGN_ORDER, \reg > -#else > - load32 PA(pa_tlb_lock), \reg > -#endif > + .macro load_process_pte_lock reg > + mfctl %cr25,\reg > + addil L%((PAGE_SIZE << PGD_ALLOC_ORDER) - PAGE_SIZE),\reg > .endm > > /* space_to_prot macro creates a prot id from a space id */ Another option might be to remove pa_serialize_tlb_flushes here: + if (unlikely(pgd == swapper_pg_dir) || pa_serialize_tlb_flushes) + return &pa_tlb_flush_lock; This might be the better solution. You have serialized the TLB purges using the pa_tlb_flush_lock. Dave -- John David Anglin dave.anglin@xxxxxxxx
