Re: [PATCH 2/2] KVM/arm64: Print emulated register table name when it is unsorted

[Marc Zyngier <maz@kernel.org>]

On Wed, 27 Apr 2022 11:21:52 +0100,
Alexandru Elisei <alexandru.elisei@arm.com> wrote:
> 
> Hi,
> 
> On Tue, Apr 26, 2022 at 10:18:27PM +0100, Marc Zyngier wrote:
> > On Mon, 25 Apr 2022 17:39:03 +0100,
> > Alexandru Elisei <alexandru.elisei@arm.com> wrote:
> > > 
> > > When a sysreg table entry is out-of-order, KVM attempts to print the
> > > address of the table:
> > > 
> > > [    0.143881] kvm [1]: sys_reg table (____ptrval____) out of order (0)
> > > 
> > > Printing the name of the table instead of a pointer is more helpful in this
> > > case:
> > > 
> > > [    0.143881] kvm [1]: sys_reg table sys_reg_descs out of order (0)
> > > 
> > > Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
> > > ---
> > >  arch/arm64/kvm/sys_regs.c | 20 +++++++++++---------
> > >  1 file changed, 11 insertions(+), 9 deletions(-)
> > > 
> > > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> > > index 57302048afd0..7b62a2daf056 100644
> > > --- a/arch/arm64/kvm/sys_regs.c
> > > +++ b/arch/arm64/kvm/sys_regs.c
> > > @@ -2188,18 +2188,18 @@ static const struct sys_reg_desc cp15_64_regs[] = {
> > >  };
> > >  
> > >  static bool check_sysreg_table(const struct sys_reg_desc *table, unsigned int n,
> > > -			       bool is_32)
> > > +			       const char *table_name, bool is_32)
> > >  {
> > >  	unsigned int i;
> > >  
> > >  	for (i = 0; i < n; i++) {
> > >  		if (!is_32 && table[i].reg && !table[i].reset) {
> > > -			kvm_err("sys_reg table %p entry %d lacks reset\n", table, i);
> > > +			kvm_err("sys_reg table %s entry %d lacks reset\n", table_name, i);
> > 
> > Instead of passing a table name, could we simply use something like
> > %pS? If this works, it would be a good indication of both what table
> > and what entry in that table is at fault.
> 
> With the change:
> 
> -                       kvm_err("sys_reg table %s out of order (%d)\n", table_name, i - 1);
> +                       kvm_err("sys_reg table %pS out of order (%d)\n", &table[i - 1], i - 1);
> 
> 
> this is what KVM prints with %pS if the second entry is out-of-order:
> 
> [    0.143698] kvm [1]: sys_reg table sys_reg_descs+0x50/0x7490 out of order (1)
> 
> There's redundant information now, the entry can be calculated from the
> table offset, but printing the offset directly is certainly convenient.
> 
> I like it more than passing the table name, if you agree I'll send a v2
> with this change.

Yup, seems like a valuable change.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

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