[PATCH V11 00/17] riscv: Add Native/Paravirt qspinlock support

[Guo Ren]

On Sun, Sep 10, 2023 at 5:32 PM Conor Dooley <conor at kernel.org> wrote:
>
> On Sun, Sep 10, 2023 at 05:16:46PM +0800, Guo Ren wrote:
> > On Sun, Sep 10, 2023 at 4:58 PM Conor Dooley <conor at kernel.org> wrote:
> > >
> > > On Sun, Sep 10, 2023 at 04:28:54AM -0400, guoren at kernel.org wrote:
> > >
> > > > Changlog:
> > > > V11:
> > > >  - Based on Leonardo Bras's cmpxchg_small patches v5.
> > > >  - Based on Guo Ren's Optimize arch_spin_value_unlocked patch v3.
> > > >  - Remove abusing alternative framework and use jump_label instead.
> > >
> > > btw, I didn't say that using alternatives was the problem, it was
> > > abusing the errata framework to perform feature detection that I had
> > > a problem with. That's not changed in v11.
> > I've removed errata feature detection. The only related patches are:
> >  - riscv: qspinlock: errata: Add ERRATA_THEAD_WRITE_ONCE fixup
> >  - riscv: qspinlock: errata: Enable qspinlock for T-HEAD processors
> >
> > Which one is your concern? Could you reply on the exact patch thread? Thx.
>
> riscv: qspinlock: errata: Enable qspinlock for T-HEAD processors
>
> Please go back and re-read the comments I left on v11 about using the
> errata code for feature detection.
>
> > > A stronger forward progress guarantee is not an erratum, AFAICT.
>
> > Sorry, there is no erratum of "stronger forward progress guarantee" in the V11.
>
> "riscv: qspinlock: errata: Enable qspinlock for T-HEAD processors" still
> uses the errata framework to detect the presence of the stronger forward
> progress guarantee in v11.
Oh, thx for pointing it out. I could replace it with this:

diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index 88690751f2ee..4be92766d3e3 100644
--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -310,7 +310,8 @@ static void __init riscv_spinlock_init(void)
 {
 #ifdef CONFIG_RISCV_COMBO_SPINLOCKS
        if (!enable_qspinlock_key &&
-           (sbi_get_firmware_id() != SBI_EXT_BASE_IMPL_ID_KVM)) {
+           (sbi_get_firmware_id() != SBI_EXT_BASE_IMPL_ID_KVM) &&
+           (sbi_get_mvendorid() != THEAD_VENDOR_ID)) {
                static_branch_disable(&combo_qspinlock_key);
                pr_info("Ticket spinlock: enabled\n");
        } else {

-- 
Best Regards
 Guo Ren