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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH v4 09/30] x86/hvm: introduce per-vCPU L3 page-table
From: Roger Pau Monné <roger.pau@xxxxxxxxxx>
The per-domain area is currently a single domain-wide structure: one L3,
referenced from every root page-table associated with the domain, so
every mapping in it is visible to every vCPU of the domain. Its
contents are already laid out in per-vCPU slices (each vCPU's
COMPAT_ARG_XLAT pages, and for PV each vCPU's GDT/LDT window and
mapcache entries), but the visibility is domain-wide. Meanwhile, much
of the per-vCPU state Xen maintains -- the VMCB, the VMX MSR load/save
areas, FPU/XSAVE state -- lives in always-mapped memory.
Allow the "per-domain" area to be per-vCPU instead ("VCPU-PT") for HVM
domains. HVM monitor tables are already per-vCPU, so this needs nothing
at context switch: every monitor table carries its vCPU's own L3 from
creation, and the per-vCPU mappings are isolated from other running
vCPUs at once. We will later build on this, adding a per-vCPU mapcache
and per-vCPU mapped areas, into which we can move the vCPU state
mentioned above.
Add pervcpu_l3_pg to the arch_vcpu struct, to correspond to the
perdomain_l3_pg in the domain struct. (We retain both so that we can
switch between per-domain and per-vCPU on a domain-by-domain basis; PV
domains always use the domain-wide one.)
In {create,destroy}_perdomain_mapping(), if d->arch.asi.vcpu_pt, use
pervcpu_l3_pg as the per-domain L3 (allocating it for a vCPU if it's
NULL, just as we allocate for a domain in !vcpu_pt mode); otherwise,
use perdomain_l3_pg. Introduce a helper, perdomain_l3(), to
consistently choose the correct one.
Introduce free_pervcpu_mappings() to free this tree, called from
arch_vcpu_destroy() on normal teardown. Since the vcpu structure holds
the only reference to pervcpu_l3_pg, arch_vcpu_create() must also call
it on its error paths: nothing else records the allocation once the
vcpu struct is torn down. The domain-wide free_perdomain_mappings()
keeps covering non-vCPU-PT domains.
init_xen_l4_slots() is given the vCPU a table is private to or, for a
table the domain's vCPUs share, any of them. Have it install that
vCPU's perdomain_l3() in slot 260: the tables a domain's vCPUs share are
PV ones, and a PV domain's vCPUs all use the domain-wide L3.
Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Assisted-by: Claude Code:claude-fable-5, Claude Code:claude-opus-4-8, Claude
Code:claude-fable-5-1, Claude Code:claude-opus-5-5
Signed-off-by: George Dunlap <gwd@xxxxxxxxxxxxxx>
---
Changes in v4:
- Rebase over earlier changes
- d->arch.vcpu_pt is now d->arch.asi.vcpu_pt.
- init_xen_l4_slots() taking a vCPU in place of the domain, and
promote_l4_table() failing while the domain has none, are now patches
of their own (Roger, Jan).
- Drop the fail_early label: every cleanup step after fail: is safe
before its setup has run (Roger).
- free_pervcpu_mappings(): clear the pointer, then free, as XFREE()
does (Roger).
- Likewise in free_perdomain_mappings().
Changes in v3:
- HVM only: PV domains keep the domain-wide area, so the PV parts go
(the single-vCPU limit, the shadow refusals, the XPTI slot install).
init_xen_l4_slots() takes the vCPU as an extra, optional argument
rather than in place of the domain, so PV guest L4s, which no vCPU
owns, are promoted exactly as before.
- Retitle (was: "x86/mm: introduce per-vCPU L3 page-table").
- free_compat_arg_xlat()'s comment names free_pervcpu_mappings() as the
teardown for a vCPU-PT domain.
Changes in v2:
- Added to the series
Changes since the previously posted version:
- Expand the commit message with the motivation and the design
rationale.
- Keep domain-wide freeing intact and introduce a vCPU-scoped
free_pervcpu_mappings() instead of re-scoping
free_perdomain_mappings(); fix the arch_vcpu_create() error-path
leaks of a partially built per-vCPU hierarchy.
- Add a perdomain_l3() helper for the root selection, rather than
open-coding the vcpu_pt choice (and testing both root pointers) at
each site.
---
xen/arch/x86/domain.c | 9 +++--
xen/arch/x86/include/asm/domain.h | 4 ++
xen/arch/x86/include/asm/mm.h | 2 +
xen/arch/x86/mm.c | 66 +++++++++++++++++++++++--------
4 files changed, 61 insertions(+), 20 deletions(-)
diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index 94a1ea904a..7a4da203d4 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -513,7 +513,7 @@ int arch_vcpu_create(struct vcpu *v)
rc = mapcache_vcpu_init(v);
if ( rc )
- return rc;
+ goto fail;
if ( !is_idle_domain(d) )
{
@@ -523,12 +523,12 @@ int arch_vcpu_create(struct vcpu *v)
*/
rc = create_perdomain_mapping(v, PERDOMAIN_VIRT_START, 0, NULL, NULL);
if ( rc )
- return rc;
+ goto fail;
paging_vcpu_init(v);
if ( (rc = vcpu_init_fpu(v)) != 0 )
- return rc;
+ goto fail;
vmce_init_vcpu(v);
@@ -576,6 +576,7 @@ int arch_vcpu_create(struct vcpu *v)
vcpu_destroy_fpu(v);
xfree(v->arch.msrs);
v->arch.msrs = NULL;
+ free_pervcpu_mappings(v);
return rc;
}
@@ -596,6 +597,8 @@ void arch_vcpu_destroy(struct vcpu *v)
pv_vcpu_destroy(v);
else
ASSERT_UNREACHABLE();
+
+ free_pervcpu_mappings(v);
}
int arch_sanitise_domain_config(const struct xen_domctl_createdomain *config)
diff --git a/xen/arch/x86/include/asm/domain.h
b/xen/arch/x86/include/asm/domain.h
index 12f79feb42..4140a92f15 100644
--- a/xen/arch/x86/include/asm/domain.h
+++ b/xen/arch/x86/include/asm/domain.h
@@ -332,6 +332,7 @@ struct monitor_write_data {
struct arch_domain
{
+ /* Domain-wide L3 for the per-domain slot; NULL in a vCPU-PT domain. */
struct page_info *perdomain_l3_pg;
/* I/O-port admin-specified access capabilities. */
@@ -688,6 +689,9 @@ struct arch_vcpu
struct vcpu_msrs *msrs;
+ /* Per-vCPU L3 for the per-domain slot; NULL in a non-vCPU-PT domain. */
+ struct page_info *pervcpu_l3_pg;
+
struct {
bool next_interrupt_enabled;
} monitor;
diff --git a/xen/arch/x86/include/asm/mm.h b/xen/arch/x86/include/asm/mm.h
index de45a111f3..12d1c06c12 100644
--- a/xen/arch/x86/include/asm/mm.h
+++ b/xen/arch/x86/include/asm/mm.h
@@ -369,6 +369,7 @@ int devalidate_page(struct page_info *page, unsigned long
type,
int preemptible);
void init_xen_pae_l2_slots(l2_pgentry_t *l2t, const struct domain *d);
+struct page_info *perdomain_l3(const struct vcpu *v);
void init_xen_l4_slots(l4_pgentry_t *l4t, mfn_t l4mfn,
const struct vcpu *v, mfn_t sl4mfn, bool ro_mpt);
bool fill_ro_mpt(mfn_t mfn);
@@ -612,6 +613,7 @@ int create_perdomain_mapping(struct vcpu *v, unsigned long
va,
void destroy_perdomain_mapping(const struct vcpu *v, unsigned long va,
unsigned int nr);
void free_perdomain_mappings(struct domain *d);
+void free_pervcpu_mappings(struct vcpu *v);
void __iomem *ioremap_wc(paddr_t pa, size_t len);
diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index ac074cc62d..362a88a300 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -1681,6 +1681,18 @@ static int promote_l3_table(struct page_info *page)
}
#endif /* CONFIG_PV */
+/*
+ * The root of the per-domain area in use by @v: the vCPU's own L3 for a
+ * vCPU-PT domain, the domain-wide one otherwise.
+ */
+struct page_info *perdomain_l3(const struct vcpu *v)
+{
+ const struct domain *d = v->domain;
+
+ return d->arch.asi.vcpu_pt ? v->arch.pervcpu_l3_pg
+ : d->arch.perdomain_l3_pg;
+}
+
/*
* Fill an L4 with Xen entries.
*
@@ -1693,7 +1705,8 @@ static int promote_l3_table(struct page_info *page)
* extended directmap.
*
* v is the vCPU the table is private to or, for a table the domain's vCPUs
- * share, any of them.
+ * share, any of them: slot 260 gets v's per-domain area (perdomain_l3()),
+ * which in a domain whose vCPUs share tables (PV) is the domain-wide one.
*/
void init_xen_l4_slots(l4_pgentry_t *l4t, mfn_t l4mfn,
const struct vcpu *v, mfn_t sl4mfn, bool ro_mpt)
@@ -1726,7 +1739,7 @@ void init_xen_l4_slots(l4_pgentry_t *l4t, mfn_t l4mfn,
/* Slot 260: Per-domain mappings. */
l4t[l4_table_offset(PERDOMAIN_VIRT_START)] =
- l4e_from_page(d->arch.perdomain_l3_pg, __PAGE_HYPERVISOR_RW);
+ l4e_from_page(perdomain_l3(v), __PAGE_HYPERVISOR_RW);
/* Slot 4: Per-domain mappings mirror. */
BUILD_BUG_ON(IS_ENABLED(CONFIG_PV32) &&
@@ -6249,7 +6262,7 @@ int create_perdomain_mapping(struct vcpu *v, unsigned
long va,
struct page_info **ppg)
{
struct domain *d = v->domain;
- struct page_info *pg;
+ struct page_info *pg, *l3_pg = perdomain_l3(v);
l3_pgentry_t *l3tab;
l2_pgentry_t *l2tab;
l1_pgentry_t *l1tab;
@@ -6258,14 +6271,17 @@ int create_perdomain_mapping(struct vcpu *v, unsigned
long va,
ASSERT(va >= PERDOMAIN_VIRT_START &&
va < PERDOMAIN_VIRT_SLOT(PERDOMAIN_SLOTS));
- if ( !d->arch.perdomain_l3_pg )
+ if ( !l3_pg )
{
pg = alloc_domheap_page(d, MEMF_no_owner);
if ( !pg )
return -ENOMEM;
l3tab = __map_domain_page(pg);
clear_page(l3tab);
- d->arch.perdomain_l3_pg = pg;
+ if ( d->arch.asi.vcpu_pt )
+ v->arch.pervcpu_l3_pg = pg;
+ else
+ d->arch.perdomain_l3_pg = pg;
if ( !nr )
{
unmap_domain_page(l3tab);
@@ -6275,7 +6291,7 @@ int create_perdomain_mapping(struct vcpu *v, unsigned
long va,
else if ( !nr )
return 0;
else
- l3tab = __map_domain_page(d->arch.perdomain_l3_pg);
+ l3tab = __map_domain_page(l3_pg);
ASSERT(!l3_table_offset(va ^ (va + nr * PAGE_SIZE - 1)));
@@ -6372,16 +6388,16 @@ void destroy_perdomain_mapping(const struct vcpu *v,
unsigned long va,
unsigned int nr)
{
const l3_pgentry_t *l3tab, *pl3e;
- const struct domain *d = v->domain;
+ struct page_info *l3_pg = perdomain_l3(v);
ASSERT(va >= PERDOMAIN_VIRT_START &&
va < PERDOMAIN_VIRT_SLOT(PERDOMAIN_SLOTS));
ASSERT(!nr || !l3_table_offset(va ^ (va + nr * PAGE_SIZE - 1)));
- if ( !d->arch.perdomain_l3_pg )
+ if ( !l3_pg )
return;
- l3tab = __map_domain_page(d->arch.perdomain_l3_pg);
+ l3tab = __map_domain_page(l3_pg);
pl3e = l3tab + l3_table_offset(va);
if ( l3e_get_flags(*pl3e) & _PAGE_PRESENT )
@@ -6420,16 +6436,11 @@ void destroy_perdomain_mapping(const struct vcpu *v,
unsigned long va,
unmap_domain_page(l3tab);
}
-void free_perdomain_mappings(struct domain *d)
+static void free_perdomain_l3(struct page_info *l3pg)
{
- l3_pgentry_t *l3tab;
+ l3_pgentry_t *l3tab = __map_domain_page(l3pg);
unsigned int i;
- if ( !d->arch.perdomain_l3_pg )
- return;
-
- l3tab = __map_domain_page(d->arch.perdomain_l3_pg);
-
for ( i = 0; i < PERDOMAIN_SLOTS; ++i)
if ( l3e_get_flags(l3tab[i]) & _PAGE_PRESENT )
{
@@ -6465,8 +6476,29 @@ void free_perdomain_mappings(struct domain *d)
}
unmap_domain_page(l3tab);
- free_domheap_page(d->arch.perdomain_l3_pg);
+ free_domheap_page(l3pg);
+}
+
+void free_perdomain_mappings(struct domain *d)
+{
+ struct page_info *l3pg = d->arch.perdomain_l3_pg;
+
+ if ( !l3pg )
+ return;
+
d->arch.perdomain_l3_pg = NULL;
+ free_perdomain_l3(l3pg);
+}
+
+void free_pervcpu_mappings(struct vcpu *v)
+{
+ struct page_info *l3pg = v->arch.pervcpu_l3_pg;
+
+ if ( !l3pg )
+ return;
+
+ v->arch.pervcpu_l3_pg = NULL;
+ free_perdomain_l3(l3pg);
}
static void write_sss_token(unsigned long *ptr)
--
2.55.0
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