On Mon, Aug 15, 2022 at 08:37:25PM +0300, Kirill A. Shutemov wrote:
> On Mon, Aug 15, 2022 at 03:42:25PM +0200, Peter Zijlstra wrote:
> > On Mon, Aug 15, 2022 at 07:17:56AM +0300, Kirill A. Shutemov wrote:
> > > diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
> > > index c1e31e9a85d7..fdc0b69b5da7 100644
> > > --- a/arch/x86/mm/tlb.c
> > > +++ b/arch/x86/mm/tlb.c
> > > @@ -154,17 +154,18 @@ static inline u16 user_pcid(u16 asid)
> > > return ret;
> > > }
> > >
> > > -static inline unsigned long build_cr3(pgd_t *pgd, u16 asid)
> > > +static inline unsigned long build_cr3(pgd_t *pgd, u16 asid, unsigned long lam)
> > > {
> > > if (static_cpu_has(X86_FEATURE_PCID)) {
> > > - return __sme_pa(pgd) | kern_pcid(asid);
> > > + return __sme_pa(pgd) | kern_pcid(asid) | lam;
> > > } else {
> > > VM_WARN_ON_ONCE(asid != 0);
> > > - return __sme_pa(pgd);
> > > + return __sme_pa(pgd) | lam;
> > > }
> > > }
> > >
> > > -static inline unsigned long build_cr3_noflush(pgd_t *pgd, u16 asid)
> > > +static inline unsigned long build_cr3_noflush(pgd_t *pgd, u16 asid,
> > > + unsigned long lam)
> > > {
> > > VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE);
> > > /*
> > > @@ -173,7 +174,7 @@ static inline unsigned long build_cr3_noflush(pgd_t *pgd, u16 asid)
> > > * boot because all CPU's the have same capabilities:
> > > */
> > > VM_WARN_ON_ONCE(!boot_cpu_has(X86_FEATURE_PCID));
> > > - return __sme_pa(pgd) | kern_pcid(asid) | CR3_NOFLUSH;
> > > + return __sme_pa(pgd) | kern_pcid(asid) | lam | CR3_NOFLUSH;
> > > }
> >
> > Looking at this; I wonder if we want something like this:
> >
> > --- a/arch/x86/mm/tlb.c
> > +++ b/arch/x86/mm/tlb.c
> > @@ -157,6 +157,7 @@ static inline u16 user_pcid(u16 asid)
> > static inline unsigned long build_cr3(pgd_t *pgd, u16 asid, unsigned long lam)
> > {
> > if (static_cpu_has(X86_FEATURE_PCID)) {
> > + VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE);
> > return __sme_pa(pgd) | kern_pcid(asid) | lam;
> > } else {
> > VM_WARN_ON_ONCE(asid != 0);
> > @@ -167,14 +168,13 @@ static inline unsigned long build_cr3(pg
> > static inline unsigned long build_cr3_noflush(pgd_t *pgd, u16 asid,
> > unsigned long lam)
> > {
> > - VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE);
> > /*
> > * Use boot_cpu_has() instead of this_cpu_has() as this function
> > * might be called during early boot. This should work even after
> > * boot because all CPU's the have same capabilities:
> > */
> > VM_WARN_ON_ONCE(!boot_cpu_has(X86_FEATURE_PCID));
> > - return __sme_pa(pgd) | kern_pcid(asid) | lam | CR3_NOFLUSH;
> > + return build_cr3(pgd, asid, lam) | CR3_NOFLUSH;
> > }
>
> Looks sane, but seems unrelated to the patch. Is it okay to fold it
> anyway?
Related in so far as that it reduces the number of sites where we have
the actual CR3 'computation' (which is how I arrived at the thing).
Arguably we could even do something like:
static inline unsigned long build_cr3(pgd_t *pgd, u16 asid, unsigned long lam)
{
unsigned long cr3 = __sme_pa(pgd) | lam;
if (static_cpu_has(X86_FEATURE_PCID)) {
VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE);
cr |= kern_pcid(asid);
} else {
VM_WARN_ON_ONCE(asid != 0);
}
return cr3;
}
But perhaps that's pushing things a little.
IMO fine to fold.
