| Message ID | 20170929150144.7602-4-george.dunlap@citrix.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
One comment below. On Fri, 2017-09-29 at 16:01 +0100, George Dunlap wrote: > There is a possibility for nested_p2m to became stale between > nestedhvm_hap_nested_page_fault() and nestedhap_fix_p2m(). At the moment > this is handled by detecting such a race inside nestedhap_fix_p2m() and > special-casing it. > > Instead, introduce p2m_get_nestedp2m_locked(), which will returned a > still-locked p2m. This allows us to call nestedhap_fix_p2m() with the > lock held and remove the code detecting the special-case. > > Signed-off-by: Sergey Dyasli <sergey.dyasli@citrix.com> > Signed-off-by: George Dunlap <george.dunlap@citrix.com> > --- > v2: > - Merged patch 9 and 10 ("x86/np2m: add p2m_get_nestedp2m_locked()" > and "x86/np2m: improve nestedhvm_hap_nested_page_fault()") > - Updated commit message > - Fix comment style in nestedhap_fix_p2m() > > CC: Andrew Cooper <andrew.cooper3@citrix.com> > CC: Jan Beulich <jbeulich@suse.com> > CC: Jun Nakajima <jun.nakajima@intel.com> > CC: Kevin Tian <kevin.tian@intel.com> > --- > xen/arch/x86/mm/hap/nested_hap.c | 31 +++++++++++++------------------ > xen/arch/x86/mm/p2m.c | 12 +++++++++--- > xen/include/asm-x86/p2m.h | 2 ++ > 3 files changed, 24 insertions(+), 21 deletions(-) > > diff --git a/xen/arch/x86/mm/hap/nested_hap.c b/xen/arch/x86/mm/hap/nested_hap.c > index ed137fa784..844b32f702 100644 > --- a/xen/arch/x86/mm/hap/nested_hap.c > +++ b/xen/arch/x86/mm/hap/nested_hap.c > @@ -101,28 +101,23 @@ nestedhap_fix_p2m(struct vcpu *v, struct p2m_domain *p2m, > unsigned int page_order, p2m_type_t p2mt, p2m_access_t p2ma) > { > int rc = 0; > + unsigned long gfn, mask; > + mfn_t mfn; > + > ASSERT(p2m); > ASSERT(p2m->set_entry); > + ASSERT(p2m_locked_by_me(p2m)); > > - p2m_lock(p2m); > - > - /* If this p2m table has been flushed or recycled under our feet, > - * leave it alone. We'll pick up the right one as we try to > - * vmenter the guest. */ > - if ( p2m->np2m_base == nhvm_vcpu_p2m_base(v) ) > - { > - unsigned long gfn, mask; > - mfn_t mfn; > - > - /* If this is a superpage mapping, round down both addresses > - * to the start of the superpage. */ > - mask = ~((1UL << page_order) - 1); > + /* > + * If this is a superpage mapping, round down both addresses to > + * the start of the superpage. > + */ > + mask = ~((1UL << page_order) - 1); > > - gfn = (L2_gpa >> PAGE_SHIFT) & mask; > - mfn = _mfn((L0_gpa >> PAGE_SHIFT) & mask); > + gfn = (L2_gpa >> PAGE_SHIFT) & mask; > + mfn = _mfn((L0_gpa >> PAGE_SHIFT) & mask); > > - rc = p2m_set_entry(p2m, gfn, mfn, page_order, p2mt, p2ma); > - } > + rc = p2m_set_entry(p2m, gfn, mfn, page_order, p2mt, p2ma); > > p2m_unlock(p2m); I have the following fixup: move p2m_unlock() out of nestedhap_fix_p2m() for balanced lock/unlock. > > @@ -212,7 +207,6 @@ nestedhvm_hap_nested_page_fault(struct vcpu *v, paddr_t *L2_gpa, > uint8_t p2ma_21 = p2m_access_rwx; > > p2m = p2m_get_hostp2m(d); /* L0 p2m */ > - nested_p2m = p2m_get_nestedp2m(v); > > /* walk the L1 P2M table */ > rv = nestedhap_walk_L1_p2m(v, *L2_gpa, &L1_gpa, &page_order_21, &p2ma_21, > @@ -278,6 +272,7 @@ nestedhvm_hap_nested_page_fault(struct vcpu *v, paddr_t *L2_gpa, > p2ma_10 &= (p2m_access_t)p2ma_21; > > /* fix p2m_get_pagetable(nested_p2m) */ > + nested_p2m = p2m_get_nestedp2m_locked(v); > nestedhap_fix_p2m(v, nested_p2m, *L2_gpa, L0_gpa, page_order_20, > p2mt_10, p2ma_10); > > diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c > index d3e602de22..aa3182dec6 100644 > --- a/xen/arch/x86/mm/p2m.c > +++ b/xen/arch/x86/mm/p2m.c > @@ -1813,7 +1813,7 @@ static void assign_np2m(struct vcpu *v, struct p2m_domain *p2m) > } > > struct p2m_domain * > -p2m_get_nestedp2m(struct vcpu *v) > +p2m_get_nestedp2m_locked(struct vcpu *v) > { > struct nestedvcpu *nv = &vcpu_nestedhvm(v); > struct domain *d = v->domain; > @@ -1838,7 +1838,6 @@ p2m_get_nestedp2m(struct vcpu *v) > hvm_asid_flush_vcpu(v); > p2m->np2m_base = np2m_base; > assign_np2m(v, p2m); > - p2m_unlock(p2m); > nestedp2m_unlock(d); > > return p2m; > @@ -1854,12 +1853,19 @@ p2m_get_nestedp2m(struct vcpu *v) > p2m->np2m_base = np2m_base; > hvm_asid_flush_vcpu(v); > assign_np2m(v, p2m); > - p2m_unlock(p2m); > nestedp2m_unlock(d); > > return p2m; > } > > +struct p2m_domain *p2m_get_nestedp2m(struct vcpu *v) > +{ > + struct p2m_domain *p2m = p2m_get_nestedp2m_locked(v); > + p2m_unlock(p2m); > + > + return p2m; > +} > + > struct p2m_domain * > p2m_get_p2m(struct vcpu *v) > { > diff --git a/xen/include/asm-x86/p2m.h b/xen/include/asm-x86/p2m.h > index 85874ab401..4a1c10c130 100644 > --- a/xen/include/asm-x86/p2m.h > +++ b/xen/include/asm-x86/p2m.h > @@ -363,6 +363,8 @@ struct p2m_domain { > * Updates vCPU's n2pm to match its np2m_base in VMCX12 and returns that np2m. > */ > struct p2m_domain *p2m_get_nestedp2m(struct vcpu *v); > +/* Similar to the above except that returned p2m is still write-locked */ > +struct p2m_domain *p2m_get_nestedp2m_locked(struct vcpu *v); > > /* If vcpu is in host mode then behaviour matches p2m_get_hostp2m(). > * If vcpu is in guest mode then behaviour matches p2m_get_nestedp2m(). -- Thanks, Sergey
diff --git a/xen/arch/x86/mm/hap/nested_hap.c b/xen/arch/x86/mm/hap/nested_hap.c index ed137fa784..844b32f702 100644 --- a/xen/arch/x86/mm/hap/nested_hap.c +++ b/xen/arch/x86/mm/hap/nested_hap.c @@ -101,28 +101,23 @@ nestedhap_fix_p2m(struct vcpu *v, struct p2m_domain *p2m, unsigned int page_order, p2m_type_t p2mt, p2m_access_t p2ma) { int rc = 0; + unsigned long gfn, mask; + mfn_t mfn; + ASSERT(p2m); ASSERT(p2m->set_entry); + ASSERT(p2m_locked_by_me(p2m)); - p2m_lock(p2m); - - /* If this p2m table has been flushed or recycled under our feet, - * leave it alone. We'll pick up the right one as we try to - * vmenter the guest. */ - if ( p2m->np2m_base == nhvm_vcpu_p2m_base(v) ) - { - unsigned long gfn, mask; - mfn_t mfn; - - /* If this is a superpage mapping, round down both addresses - * to the start of the superpage. */ - mask = ~((1UL << page_order) - 1); + /* + * If this is a superpage mapping, round down both addresses to + * the start of the superpage. + */ + mask = ~((1UL << page_order) - 1); - gfn = (L2_gpa >> PAGE_SHIFT) & mask; - mfn = _mfn((L0_gpa >> PAGE_SHIFT) & mask); + gfn = (L2_gpa >> PAGE_SHIFT) & mask; + mfn = _mfn((L0_gpa >> PAGE_SHIFT) & mask); - rc = p2m_set_entry(p2m, gfn, mfn, page_order, p2mt, p2ma); - } + rc = p2m_set_entry(p2m, gfn, mfn, page_order, p2mt, p2ma); p2m_unlock(p2m); @@ -212,7 +207,6 @@ nestedhvm_hap_nested_page_fault(struct vcpu *v, paddr_t *L2_gpa, uint8_t p2ma_21 = p2m_access_rwx; p2m = p2m_get_hostp2m(d); /* L0 p2m */ - nested_p2m = p2m_get_nestedp2m(v); /* walk the L1 P2M table */ rv = nestedhap_walk_L1_p2m(v, *L2_gpa, &L1_gpa, &page_order_21, &p2ma_21, @@ -278,6 +272,7 @@ nestedhvm_hap_nested_page_fault(struct vcpu *v, paddr_t *L2_gpa, p2ma_10 &= (p2m_access_t)p2ma_21; /* fix p2m_get_pagetable(nested_p2m) */ + nested_p2m = p2m_get_nestedp2m_locked(v); nestedhap_fix_p2m(v, nested_p2m, *L2_gpa, L0_gpa, page_order_20, p2mt_10, p2ma_10); diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c index d3e602de22..aa3182dec6 100644 --- a/xen/arch/x86/mm/p2m.c +++ b/xen/arch/x86/mm/p2m.c @@ -1813,7 +1813,7 @@ static void assign_np2m(struct vcpu *v, struct p2m_domain *p2m) } struct p2m_domain * -p2m_get_nestedp2m(struct vcpu *v) +p2m_get_nestedp2m_locked(struct vcpu *v) { struct nestedvcpu *nv = &vcpu_nestedhvm(v); struct domain *d = v->domain; @@ -1838,7 +1838,6 @@ p2m_get_nestedp2m(struct vcpu *v) hvm_asid_flush_vcpu(v); p2m->np2m_base = np2m_base; assign_np2m(v, p2m); - p2m_unlock(p2m); nestedp2m_unlock(d); return p2m; @@ -1854,12 +1853,19 @@ p2m_get_nestedp2m(struct vcpu *v) p2m->np2m_base = np2m_base; hvm_asid_flush_vcpu(v); assign_np2m(v, p2m); - p2m_unlock(p2m); nestedp2m_unlock(d); return p2m; } +struct p2m_domain *p2m_get_nestedp2m(struct vcpu *v) +{ + struct p2m_domain *p2m = p2m_get_nestedp2m_locked(v); + p2m_unlock(p2m); + + return p2m; +} + struct p2m_domain * p2m_get_p2m(struct vcpu *v) { diff --git a/xen/include/asm-x86/p2m.h b/xen/include/asm-x86/p2m.h index 85874ab401..4a1c10c130 100644 --- a/xen/include/asm-x86/p2m.h +++ b/xen/include/asm-x86/p2m.h @@ -363,6 +363,8 @@ struct p2m_domain { * Updates vCPU's n2pm to match its np2m_base in VMCX12 and returns that np2m. */ struct p2m_domain *p2m_get_nestedp2m(struct vcpu *v); +/* Similar to the above except that returned p2m is still write-locked */ +struct p2m_domain *p2m_get_nestedp2m_locked(struct vcpu *v); /* If vcpu is in host mode then behaviour matches p2m_get_hostp2m(). * If vcpu is in guest mode then behaviour matches p2m_get_nestedp2m().