On 12/04/2019 17:39, Tamas K Lengyel wrote:
> The p2m_altp2m_lazy_copy is responsible for lazily populating an altp2m view
> when the guest traps out due to no EPT entry being present in the active view.
> Currently the function took several inputs that it didn't use and also
> locked/unlocked gfns when it didn't need to.
>
> Signed-off-by: Tamas K Lengyel <ta...@tklengyel.com>
Re-reveiwing in light of the discussion.
> diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
> index b9bbb8f485..140c707348 100644
> --- a/xen/arch/x86/mm/p2m.c
> +++ b/xen/arch/x86/mm/p2m.c
> @@ -2375,54 +2375,46 @@ bool_t p2m_switch_vcpu_altp2m_by_id(struct vcpu *v,
> unsigned int idx)
> * indicate that outer handler should handle fault
> */
>
> -bool_t p2m_altp2m_lazy_copy(struct vcpu *v, paddr_t gpa,
> - unsigned long gla, struct npfec npfec,
> - struct p2m_domain **ap2m)
> +bool_t p2m_altp2m_lazy_copy(struct p2m_domain *ap2m, unsigned long gfn_l,
> + mfn_t hmfn, p2m_type_t hp2mt, p2m_access_t hp2ma,
> + unsigned int page_order)
> {
> - struct p2m_domain *hp2m = p2m_get_hostp2m(v->domain);
> - p2m_type_t p2mt;
> - p2m_access_t p2ma;
> - unsigned int page_order;
> - gfn_t gfn = _gfn(paddr_to_pfn(gpa));
> + p2m_type_t ap2mt;
> + p2m_access_t ap2ma;
> unsigned long mask;
> - mfn_t mfn;
> + gfn_t gfn;
> + mfn_t amfn;
> int rv;
>
> - *ap2m = p2m_get_altp2m(v);
> -
> - mfn = get_gfn_type_access(*ap2m, gfn_x(gfn), &p2mt, &p2ma,
> - 0, &page_order);
> - __put_gfn(*ap2m, gfn_x(gfn));
> -
> - if ( !mfn_eq(mfn, INVALID_MFN) )
> - return 0;
With the rearranged logic, and feeding in some of my cleanup series, you
want something like this:
/* Entry not present in hp2m? Caller should handle the fault. */
if ( mfn_eq(hmfn, INVALID_MFN) )
return 0;
There is no point doing the ap2m lookup if you're going to bail because
of the hp2m miss anyway.
> + p2m_lock(ap2m);
>
> - mfn = get_gfn_type_access(hp2m, gfn_x(gfn), &p2mt, &p2ma,
> - P2M_ALLOC, &page_order);
> - __put_gfn(hp2m, gfn_x(gfn));
> + amfn = __get_gfn_type_access(ap2m, gfn_l, &ap2mt, &ap2ma,
> + 0, NULL, false);
>
> - if ( mfn_eq(mfn, INVALID_MFN) )
> + /* Bail if entry is already in altp2m or there is no entry is hostp2m */
This comment then reduces to:
/* Entry already present in ap2m? Caller should handle the fault. */
> + if ( !mfn_eq(amfn, INVALID_MFN) || mfn_eq(hmfn, INVALID_MFN) )
> + {
> + p2m_unlock(ap2m);
> return 0;
> -
> - p2m_lock(*ap2m);
> + }
>
> /*
> * If this is a superpage mapping, round down both frame numbers
> * to the start of the superpage.
> */
> mask = ~((1UL << page_order) - 1);
> - mfn = _mfn(mfn_x(mfn) & mask);
> - gfn = _gfn(gfn_x(gfn) & mask);
> + hmfn = _mfn(mfn_x(hmfn) & mask);
> + gfn = _gfn(gfn_l & mask);
>
> - rv = p2m_set_entry(*ap2m, gfn, mfn, page_order, p2mt, p2ma);
> - p2m_unlock(*ap2m);
> + rv = p2m_set_entry(ap2m, gfn, hmfn, page_order, hp2mt, hp2ma);
> + p2m_unlock(ap2m);
>
> if ( rv )
> {
> gdprintk(XENLOG_ERR,
> - "failed to set entry for %#"PRIx64" -> %#"PRIx64" p2m %#"PRIx64"\n",
> - gfn_x(gfn), mfn_x(mfn), (unsigned long)*ap2m);
> - domain_crash(hp2m->domain);
> + "failed to set entry for %#"PRIx64" -> %#"PRIx64" p2m %#"PRIx64"\n",
> + gfn_l, mfn_x(hmfn), (unsigned long)ap2m);
This should be a gprintk(), not a gdprintk(), because there is nothing
more infuriating in release builds than a domain_crash() with no
qualification.
Printing the virtual address of the ap2m is also useless as far as
diagnostics go. How about something like:
"Failed to lazy copy gfn %"PRI_gfn" -> %"PRI_mfn" (type %u, access %u,
order %u) for view %u\n"
if there is an easy way to access the view id. This at least stands a
chance of being useful when debugging.
> + domain_crash(ap2m->domain);
> }
>
> return 1;
> diff --git a/xen/include/asm-x86/p2m.h b/xen/include/asm-x86/p2m.h
> index 2801a8ccca..c25e2a3cd8 100644
> --- a/xen/include/asm-x86/p2m.h
> +++ b/xen/include/asm-x86/p2m.h
> @@ -867,8 +867,9 @@ void p2m_altp2m_check(struct vcpu *v, uint16_t idx);
> void p2m_flush_altp2m(struct domain *d);
>
> /* Alternate p2m paging */
> -bool_t p2m_altp2m_lazy_copy(struct vcpu *v, paddr_t gpa,
> - unsigned long gla, struct npfec npfec, struct p2m_domain **ap2m);
> +bool_t p2m_altp2m_lazy_copy(struct p2m_domain *ap2m, unsigned long gfn_l,
> + mfn_t hmfn, p2m_type_t hp2mt, p2m_access_t hp2ma,
> + unsigned int page_order);
Can we switch to bool while changing everything else as well?
Thanks,
~Andrew
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