Mailing List Archive

[PATCH v2 10/12] x86/p2m: {get,set}_entry hooks and p2m-pt.c are HVM-only
With the hooks no longer needing setting, p2m_pt_init() degenerates to
(about) nothing when !HVM. As a result, p2m-pt.c doesn't need building
anymore in this case, as long as p2m_pt_init() has proper surrogates put
in place.

Unfortunately this means some new #ifdef-ary in p2m.c, but the mid-term
plan there is to get rid of (almost) all of it by splitting out the then
hopefully very few remaining non-HVM pieces.

While the movement of the paging_mode_translate() check from
p2m_remove_page() to guest_physmap_remove_page() may not be strictly
necessary anymore (it was in an early version of this change), it looks
more logical to live in the latter function, allowing to avoid acquiring
the lock in the PV case. All other callers of p2m_remove_page() already
have such a check anyway (in the altp2m case up the call stack).

Signed-off-by: Jan Beulich <jbeulich@suse.com>
---
v2: New.

--- a/xen/arch/x86/mm/Makefile
+++ b/xen/arch/x86/mm/Makefile
@@ -7,8 +7,8 @@ obj-$(CONFIG_SHADOW_PAGING) += guest_wal
obj-$(CONFIG_MEM_ACCESS) += mem_access.o
obj-$(CONFIG_MEM_PAGING) += mem_paging.o
obj-$(CONFIG_MEM_SHARING) += mem_sharing.o
-obj-y += p2m.o p2m-pt.o
-obj-$(CONFIG_HVM) += p2m-ept.o p2m-pod.o
+obj-y += p2m.o
+obj-$(CONFIG_HVM) += p2m-ept.o p2m-pod.o p2m-pt.o
obj-y += paging.o

guest_walk_%.o: guest_walk.c Makefile
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -494,8 +494,10 @@ mfn_t __get_gfn_type_access(struct p2m_d
p2m_type_t *t, p2m_access_t *a, p2m_query_t q,
unsigned int *page_order, bool_t locked)
{
+#ifdef CONFIG_HVM
mfn_t mfn;
gfn_t gfn = _gfn(gfn_l);
+#endif

/* Unshare makes no sense withuot populate. */
if ( q & P2M_UNSHARE )
@@ -509,6 +511,7 @@ mfn_t __get_gfn_type_access(struct p2m_d
return _mfn(gfn_l);
}

+#ifdef CONFIG_HVM
if ( locked )
/* Grab the lock here, don't release until put_gfn */
gfn_lock(p2m, gfn, 0);
@@ -542,6 +545,7 @@ mfn_t __get_gfn_type_access(struct p2m_d
}

return mfn;
+#endif
}

void __put_gfn(struct p2m_domain *p2m, unsigned long gfn)
@@ -620,6 +624,7 @@ struct page_info *p2m_get_page_from_gfn(
return page;
}

+#ifdef CONFIG_HVM
/* Returns: 0 for success, -errno for failure */
int p2m_set_entry(struct p2m_domain *p2m, gfn_t gfn, mfn_t mfn,
unsigned int page_order, p2m_type_t p2mt, p2m_access_t p2ma)
@@ -659,6 +664,7 @@ int p2m_set_entry(struct p2m_domain *p2m

return rc;
}
+#endif

mfn_t p2m_alloc_ptp(struct p2m_domain *p2m, unsigned int level)
{
@@ -777,6 +783,8 @@ void p2m_final_teardown(struct domain *d
p2m_teardown_hostp2m(d);
}

+#ifdef CONFIG_HVM
+
static int __must_check
p2m_remove_page(struct p2m_domain *p2m, gfn_t gfn, mfn_t mfn,
unsigned int page_order)
@@ -785,10 +793,6 @@ p2m_remove_page(struct p2m_domain *p2m,
p2m_type_t t;
p2m_access_t a;

- /* IOMMU for PV guests is handled in get_page_type() and put_page(). */
- if ( !paging_mode_translate(p2m->domain) )
- return 0;
-
ASSERT(gfn_locked_by_me(p2m, gfn));
P2M_DEBUG("removing gfn=%#lx mfn=%#lx\n", gfn_x(gfn), mfn_x(mfn));

@@ -829,6 +833,10 @@ guest_physmap_remove_page(struct domain
struct p2m_domain *p2m = p2m_get_hostp2m(d);
int rc;

+ /* IOMMU for PV guests is handled in get_page_type() and put_page(). */
+ if ( !paging_mode_translate(d) )
+ return 0;
+
gfn_lock(p2m, gfn, page_order);
rc = p2m_remove_page(p2m, gfn, mfn, page_order);
gfn_unlock(p2m, gfn, page_order);
@@ -836,6 +844,8 @@ guest_physmap_remove_page(struct domain
return rc;
}

+#endif /* CONFIG_HVM */
+
int
guest_physmap_add_page(struct domain *d, gfn_t gfn, mfn_t mfn,
unsigned int page_order)
@@ -1400,14 +1410,16 @@ int clear_mmio_p2m_entry(struct domain *
int set_identity_p2m_entry(struct domain *d, unsigned long gfn_l,
p2m_access_t p2ma, unsigned int flag)
{
+#ifdef CONFIG_HVM
p2m_type_t p2mt;
p2m_access_t a;
gfn_t gfn = _gfn(gfn_l);
mfn_t mfn;
struct p2m_domain *p2m = p2m_get_hostp2m(d);
int ret;
+#endif

- if ( !paging_mode_translate(p2m->domain) )
+ if ( !paging_mode_translate(d) )
{
if ( !is_iommu_enabled(d) )
return 0;
@@ -1416,6 +1428,7 @@ int set_identity_p2m_entry(struct domain
IOMMUF_readable | IOMMUF_writable);
}

+#ifdef CONFIG_HVM
gfn_lock(p2m, gfn, 0);

mfn = p2m->get_entry(p2m, gfn, &p2mt, &a, 0, NULL, NULL);
@@ -1439,16 +1452,19 @@ int set_identity_p2m_entry(struct domain

gfn_unlock(p2m, gfn, 0);
return ret;
+#endif
}

int clear_identity_p2m_entry(struct domain *d, unsigned long gfn_l)
{
+#ifdef CONFIG_HVM
p2m_type_t p2mt;
p2m_access_t a;
gfn_t gfn = _gfn(gfn_l);
mfn_t mfn;
struct p2m_domain *p2m = p2m_get_hostp2m(d);
int ret;
+#endif

if ( !paging_mode_translate(d) )
{
@@ -1457,6 +1473,7 @@ int clear_identity_p2m_entry(struct doma
return iommu_legacy_unmap(d, _dfn(gfn_l), 1ul << PAGE_ORDER_4K);
}

+#ifdef CONFIG_HVM
gfn_lock(p2m, gfn, 0);

mfn = p2m->get_entry(p2m, gfn, &p2mt, &a, 0, NULL, NULL);
@@ -1476,6 +1493,7 @@ int clear_identity_p2m_entry(struct doma
}

return ret;
+#endif
}

#ifdef CONFIG_MEM_SHARING
--- a/xen/arch/x86/mm/p2m-pt.c
+++ b/xen/arch/x86/mm/p2m-pt.c
@@ -324,7 +324,6 @@ p2m_next_level(struct p2m_domain *p2m, v
return rc;
}

-#ifdef CONFIG_HVM
/*
* Mark (via clearing the U flag) as needing P2M type re-calculation all valid
* present entries at the targeted level for the passed in GFN range, which is
@@ -393,7 +392,6 @@ static int p2m_pt_set_recalc_range(struc

return err;
}
-#endif /* CONFIG_HVM */

/*
* Handle possibly necessary P2M type re-calculation (U flag clear for a
@@ -932,8 +930,6 @@ pod_retry_l1:
return (p2m_is_valid(*t) || p2m_is_any_ram(*t)) ? mfn : INVALID_MFN;
}

-#ifdef CONFIG_HVM
-
static void p2m_pt_change_entry_type_global(struct p2m_domain *p2m,
p2m_type_t ot, p2m_type_t nt)
{
@@ -1015,8 +1011,6 @@ static int p2m_pt_change_entry_type_rang
return err;
}

-#endif /* CONFIG_HVM */
-
#if P2M_AUDIT
static long p2m_pt_audit_p2m(struct p2m_domain *p2m)
{
@@ -1173,11 +1167,9 @@ void p2m_pt_init(struct p2m_domain *p2m)
{
p2m->set_entry = p2m_pt_set_entry;
p2m->get_entry = p2m_pt_get_entry;
-#ifdef CONFIG_HVM
p2m->recalc = do_recalc;
p2m->change_entry_type_global = p2m_pt_change_entry_type_global;
p2m->change_entry_type_range = p2m_pt_change_entry_type_range;
-#endif

/* Still too early to use paging_mode_hap(). */
if ( hap_enabled(p2m->domain) )
--- a/xen/include/asm-x86/p2m.h
+++ b/xen/include/asm-x86/p2m.h
@@ -251,6 +251,7 @@ struct p2m_domain {
/* Pages used to construct the p2m */
struct page_list_head pages;

+#ifdef CONFIG_HVM
int (*set_entry)(struct p2m_domain *p2m,
gfn_t gfn,
mfn_t mfn, unsigned int page_order,
@@ -264,7 +265,6 @@ struct p2m_domain {
p2m_query_t q,
unsigned int *page_order,
bool_t *sve);
-#ifdef CONFIG_HVM
int (*recalc)(struct p2m_domain *p2m,
unsigned long gfn);
void (*enable_hardware_log_dirty)(struct p2m_domain *p2m);
@@ -785,8 +785,14 @@ int __must_check p2m_set_entry(struct p2
unsigned int page_order, p2m_type_t p2mt,
p2m_access_t p2ma);

+#if defined(CONFIG_HVM)
/* Set up function pointers for PT implementation: only for use by p2m code */
extern void p2m_pt_init(struct p2m_domain *p2m);
+#elif defined(CONFIG_SHADOW_PAGING)
+# define p2m_pt_init shadow_p2m_init
+#else
+static inline void p2m_pt_init(struct p2m_domain *p2m) {}
+#endif

void *map_domain_gfn(struct p2m_domain *p2m, gfn_t gfn, mfn_t *mfn,
p2m_query_t q, uint32_t *pfec);
--- a/xen/include/xen/p2m-common.h
+++ b/xen/include/xen/p2m-common.h
@@ -8,9 +8,18 @@ int set_foreign_p2m_entry(struct domain
unsigned long gfn, mfn_t mfn);

/* Remove a page from a domain's p2m table */
+#ifdef CONFIG_HVM
int __must_check
guest_physmap_remove_page(struct domain *d, gfn_t gfn, mfn_t mfn,
unsigned int page_order);
+#else
+static inline int
+guest_physmap_remove_page(struct domain *d, gfn_t gfn, mfn_t mfn,
+ unsigned int page_order)
+{
+ return 0;
+}
+#endif

/* Map MMIO regions in the p2m: start_gfn and nr describe the range in
* * the guest physical address space to map, starting from the machine
Re: [PATCH v2 10/12] x86/p2m: {get,set}_entry hooks and p2m-pt.c are HVM-only [ In reply to ]
On Mon, Apr 12, 2021 at 04:13:19PM +0200, Jan Beulich wrote:
> With the hooks no longer needing setting, p2m_pt_init() degenerates to
> (about) nothing when !HVM. As a result, p2m-pt.c doesn't need building
> anymore in this case, as long as p2m_pt_init() has proper surrogates put
> in place.
>
> Unfortunately this means some new #ifdef-ary in p2m.c, but the mid-term
> plan there is to get rid of (almost) all of it by splitting out the then
> hopefully very few remaining non-HVM pieces.
>
> While the movement of the paging_mode_translate() check from
> p2m_remove_page() to guest_physmap_remove_page() may not be strictly
> necessary anymore (it was in an early version of this change), it looks
> more logical to live in the latter function, allowing to avoid acquiring
> the lock in the PV case. All other callers of p2m_remove_page() already
> have such a check anyway (in the altp2m case up the call stack).
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Acked-by: Roger Pau Monné <roger.pau@citrix.com>

Thanks, Roger.