Re: [PATCH v4 02/18] xen/riscv: introduce VMID allocation and manegement

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

On 9/19/25 11:26 PM, Jan Beulich wrote:

> On 17.09.2025 23:55, Oleksii Kurochko wrote:
> > @@ -151,6 +152,8 @@ void __init noreturn start_xen(unsigned long bootcpu_id,
> >  
> >      gstage_mode_detect();
> >  
> > +    vmid_init();
> >       
> Like for the earlier patch, I'm not convinced this is a function good
> to call from the top-level start_xen(). The two functions sitting side
> by side actually demonstrates the scalability issue pretty well.
>     
In the case of vmid_init(), it could be a good place to call it here since
vmid_init() is expected to be called once when a pCPU is booted. For the boot
CPU, all "setup" functions are called in start_xen(), so vmid_init() could
potentially be called there as well.

For other (non-boot) CPUs, vmid_init() could be called somewhere in the
__cpu_up() code or at the CPU’s entry point.

> > --- /dev/null
> > +++ b/xen/arch/riscv/vmid.c
> > @@ -0,0 +1,193 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only */
> > +
> > +#include <xen/domain.h>
> > +#include <xen/init.h>
> > +#include <xen/sections.h>
> > +#include <xen/lib.h>
> > +#include <xen/param.h>
> > +#include <xen/percpu.h>
> > +
> > +#include <asm/atomic.h>
> > +#include <asm/csr.h>
> > +#include <asm/flushtlb.h>
> > +#include <asm/p2m.h>
> > +
> > +/* Xen command-line option to enable VMIDs */
> > +static bool __ro_after_init opt_vmid_use_enabled = true;
> > +boolean_param("vmid", opt_vmid_use_enabled);
> >       
> Is there a particular reason to not have the variable be simply opt_vmid,
> properly in sync with the command line option?
>     
There is no a specific reason for that, just made it in sync with x86.
opt_vmid could be used instead. I will do s/opt_vmid_use_enabled/opt_vmid.

> > +void vcpu_vmid_flush_vcpu(struct vcpu *v)
> >       
> An reason to have two "vcpu" in the name?
>     
The first "vcpu" should be really dropped.

Thanks.

~ Oleksii