* [Xen-devel] [PATCH v7 0/3] purge free_shared_domheap_page()
@ 2020-01-29 17:10 Paul Durrant
2020-01-29 17:10 ` [Xen-devel] [PATCH v7 1/3] x86 / vmx: move teardown from domain_destroy() Paul Durrant
` (2 more replies)
0 siblings, 3 replies; 9+ messages in thread
From: Paul Durrant @ 2020-01-29 17:10 UTC (permalink / raw)
To: xen-devel; +Cc: Paul Durrant
Drop "mm: modify domain_adjust_tot_pages() to better handle a zero
adjustment".
Paul Durrant (3):
x86 / vmx: move teardown from domain_destroy()...
mm: make pages allocated with MEMF_no_refcount safe to assign
x86 / vmx: use a MEMF_no_refcount domheap page for
APIC_DEFAULT_PHYS_BASE
xen/arch/x86/hvm/vmx/vmx.c | 25 +++++++++++++++----
xen/arch/x86/mm.c | 15 ++++--------
xen/common/page_alloc.c | 49 ++++++++++++++++++++++++++++----------
xen/include/asm-arm/mm.h | 5 +++-
xen/include/asm-x86/mm.h | 9 +++----
xen/include/xen/sched.h | 18 +++++++-------
6 files changed, 80 insertions(+), 41 deletions(-)
--
2.20.1
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^ permalink raw reply [flat|nested] 9+ messages in thread
* [Xen-devel] [PATCH v7 1/3] x86 / vmx: move teardown from domain_destroy()...
2020-01-29 17:10 [Xen-devel] [PATCH v7 0/3] purge free_shared_domheap_page() Paul Durrant
@ 2020-01-29 17:10 ` Paul Durrant
2020-02-03 8:08 ` Tian, Kevin
2020-01-29 17:10 ` [Xen-devel] [PATCH v7 2/3] mm: make pages allocated with MEMF_no_refcount safe to assign Paul Durrant
2020-01-29 17:10 ` [Xen-devel] [PATCH v7 3/3] x86 / vmx: use a MEMF_no_refcount domheap page for APIC_DEFAULT_PHYS_BASE Paul Durrant
2 siblings, 1 reply; 9+ messages in thread
From: Paul Durrant @ 2020-01-29 17:10 UTC (permalink / raw)
To: xen-devel
Cc: Kevin Tian, Jun Nakajima, Wei Liu, Andrew Cooper, Paul Durrant,
George Dunlap, Roger Pau Monné
... to domain_relinquish_resources().
The teardown code frees the APICv page. This does not need to be done late
so do it in domain_relinquish_resources() rather than domain_destroy().
Signed-off-by: Paul Durrant <pdurrant@amazon.com>
---
Cc: Jun Nakajima <jun.nakajima@intel.com>
Cc: Kevin Tian <kevin.tian@intel.com>
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Wei Liu <wl@xen.org>
Cc: "Roger Pau Monné" <roger.pau@citrix.com>
Cc: George Dunlap <george.dunlap@citrix.com>
v4:
- New in v4 (disaggregated from v3 patch #3)
---
xen/arch/x86/hvm/vmx/vmx.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index b262d38a7c..606f3dc2eb 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -419,7 +419,7 @@ static int vmx_domain_initialise(struct domain *d)
return 0;
}
-static void vmx_domain_destroy(struct domain *d)
+static void vmx_domain_relinquish_resources(struct domain *d)
{
if ( !has_vlapic(d) )
return;
@@ -2240,7 +2240,7 @@ static struct hvm_function_table __initdata vmx_function_table = {
.cpu_up_prepare = vmx_cpu_up_prepare,
.cpu_dead = vmx_cpu_dead,
.domain_initialise = vmx_domain_initialise,
- .domain_destroy = vmx_domain_destroy,
+ .domain_relinquish_resources = vmx_domain_relinquish_resources,
.vcpu_initialise = vmx_vcpu_initialise,
.vcpu_destroy = vmx_vcpu_destroy,
.save_cpu_ctxt = vmx_save_vmcs_ctxt,
--
2.20.1
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^ permalink raw reply related [flat|nested] 9+ messages in thread
* [Xen-devel] [PATCH v7 2/3] mm: make pages allocated with MEMF_no_refcount safe to assign
2020-01-29 17:10 [Xen-devel] [PATCH v7 0/3] purge free_shared_domheap_page() Paul Durrant
2020-01-29 17:10 ` [Xen-devel] [PATCH v7 1/3] x86 / vmx: move teardown from domain_destroy() Paul Durrant
@ 2020-01-29 17:10 ` Paul Durrant
2020-01-30 10:19 ` Jan Beulich
2020-01-30 11:02 ` Jan Beulich
2020-01-29 17:10 ` [Xen-devel] [PATCH v7 3/3] x86 / vmx: use a MEMF_no_refcount domheap page for APIC_DEFAULT_PHYS_BASE Paul Durrant
2 siblings, 2 replies; 9+ messages in thread
From: Paul Durrant @ 2020-01-29 17:10 UTC (permalink / raw)
To: xen-devel
Cc: Stefano Stabellini, Julien Grall, Wei Liu, Konrad Rzeszutek Wilk,
George Dunlap, Andrew Cooper, Paul Durrant, Ian Jackson,
Volodymyr Babchuk, Roger Pau Monné
Currently it is unsafe to assign a domheap page allocated with
MEMF_no_refcount to a domain because the domain't 'tot_pages' will not
be incremented, but will be decrement when the page is freed (since
free_domheap_pages() has no way of telling that the increment was skipped).
This patch allocates a new 'count_info' bit for a PGC_extra flag
which is then used to mark pages when alloc_domheap_pages() is called
with MEMF_no_refcount. The MEMF_no_refcount is *not* passed through to
assign_pages() because it still needs to call domain_adjust_tot_pages() to
make sure the domain is appropriately referenced. assign_pages() is
accordingly modified to account pages marked with PGC_extra to an
'extra_pages' counter, which is then subtracted from 'tot_pages' before it
is checked against 'max_pages', thus avoiding over-allocation errors.
NOTE: steal_page() is also modified to decrement extra_pages in the case of
a PGC_extra page being stolen from a domain.
Also, whilst adding the extra_pages counter into struct domain, make
some cosmetic fixes to comments for neighbouring fields.
Signed-off-by: Paul Durrant <pdurrant@amazon.com>
---
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: George Dunlap <George.Dunlap@eu.citrix.com>
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Julien Grall <julien@xen.org>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Wei Liu <wl@xen.org>
Cc: Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
Cc: "Roger Pau Monné" <roger.pau@citrix.com>
v7:
- s/PGC_no_refcount/PGC_extra/g
- Re-work allocation to account for 'extra' pages, also making it
safe to assign PGC_extra pages post-allocation
v6:
- Add an extra ASSERT into assign_pages() that PGC_no_refcount is not
set if MEMF_no_refcount is clear
- ASSERT that count_info is 0 in alloc_domheap_pages() and set to
PGC_no_refcount rather than ORing
v5:
- Make sure PGC_no_refcount is set before assign_pages() is called
- Don't bother to clear PGC_no_refcount in free_domheap_pages() and
drop ASSERT in free_heap_pages()
- Don't latch count_info in free_heap_pages()
v4:
- New in v4
---
xen/arch/x86/mm.c | 5 ++++
xen/common/page_alloc.c | 49 +++++++++++++++++++++++++++++-----------
xen/include/asm-arm/mm.h | 5 +++-
xen/include/asm-x86/mm.h | 7 ++++--
xen/include/xen/sched.h | 18 ++++++++-------
5 files changed, 60 insertions(+), 24 deletions(-)
diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index f50c065af3..5b04db8c21 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -4266,6 +4266,11 @@ int steal_page(
page_list_del(page, &d->page_list);
/* Unlink from original owner. */
+ if ( page->count_info & PGC_extra )
+ {
+ ASSERT(d->extra_pages);
+ d->extra_pages--;
+ }
if ( !(memflags & MEMF_no_refcount) && !domain_adjust_tot_pages(d, -1) )
drop_dom_ref = true;
diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index 919a270587..a2d69f222a 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -2256,6 +2256,7 @@ int assign_pages(
{
int rc = 0;
unsigned long i;
+ unsigned int extra_pages = 0;
spin_lock(&d->page_alloc_lock);
@@ -2267,13 +2268,19 @@ int assign_pages(
goto out;
}
+ for ( i = 0; i < (1 << order); i++ )
+ if ( pg[i].count_info & PGC_extra )
+ extra_pages++;
+
if ( !(memflags & MEMF_no_refcount) )
{
- if ( unlikely((d->tot_pages + (1 << order)) > d->max_pages) )
+ unsigned int max_pages = d->max_pages - d->extra_pages - extra_pages;
+
+ if ( unlikely((d->tot_pages + (1 << order)) > max_pages) )
{
gprintk(XENLOG_INFO, "Over-allocation for domain %u: "
"%u > %u\n", d->domain_id,
- d->tot_pages + (1 << order), d->max_pages);
+ d->tot_pages + (1 << order), max_pages);
rc = -E2BIG;
goto out;
}
@@ -2282,13 +2289,17 @@ int assign_pages(
get_knownalive_domain(d);
}
+ d->extra_pages += extra_pages;
for ( i = 0; i < (1 << order); i++ )
{
+ unsigned long count_info = pg[i].count_info;
+
ASSERT(page_get_owner(&pg[i]) == NULL);
- ASSERT(!pg[i].count_info);
+ ASSERT(!(count_info & ~PGC_extra));
page_set_owner(&pg[i], d);
smp_wmb(); /* Domain pointer must be visible before updating refcnt. */
- pg[i].count_info = PGC_allocated | 1;
+ count_info &= PGC_extra;
+ pg[i].count_info = count_info | PGC_allocated | 1;
page_list_add_tail(&pg[i], &d->page_list);
}
@@ -2314,11 +2325,6 @@ struct page_info *alloc_domheap_pages(
if ( memflags & MEMF_no_owner )
memflags |= MEMF_no_refcount;
- else if ( (memflags & MEMF_no_refcount) && d )
- {
- ASSERT(!(memflags & MEMF_no_refcount));
- return NULL;
- }
if ( !dma_bitsize )
memflags &= ~MEMF_no_dma;
@@ -2331,11 +2337,23 @@ struct page_info *alloc_domheap_pages(
memflags, d)) == NULL)) )
return NULL;
- if ( d && !(memflags & MEMF_no_owner) &&
- assign_pages(d, pg, order, memflags) )
+ if ( d && !(memflags & MEMF_no_owner) )
{
- free_heap_pages(pg, order, memflags & MEMF_no_scrub);
- return NULL;
+ if ( memflags & MEMF_no_refcount )
+ {
+ unsigned long i;
+
+ for ( i = 0; i < (1ul << order); i++ )
+ {
+ ASSERT(!pg[i].count_info);
+ pg[i].count_info = PGC_extra;
+ }
+ }
+ if ( assign_pages(d, pg, order, memflags & ~MEMF_no_refcount) )
+ {
+ free_heap_pages(pg, order, memflags & MEMF_no_scrub);
+ return NULL;
+ }
}
return pg;
@@ -2383,6 +2401,11 @@ void free_domheap_pages(struct page_info *pg, unsigned int order)
BUG();
}
arch_free_heap_page(d, &pg[i]);
+ if ( pg[i].count_info & PGC_extra )
+ {
+ ASSERT(d->extra_pages);
+ d->extra_pages--;
+ }
}
drop_dom_ref = !domain_adjust_tot_pages(d, -(1 << order));
diff --git a/xen/include/asm-arm/mm.h b/xen/include/asm-arm/mm.h
index 333efd3a60..7df91280bc 100644
--- a/xen/include/asm-arm/mm.h
+++ b/xen/include/asm-arm/mm.h
@@ -119,9 +119,12 @@ struct page_info
#define PGC_state_offlined PG_mask(2, 9)
#define PGC_state_free PG_mask(3, 9)
#define page_state_is(pg, st) (((pg)->count_info&PGC_state) == PGC_state_##st)
+/* Page is not reference counted */
+#define _PGC_extra PG_shift(10)
+#define PGC_extra PG_mask(1, 10)
/* Count of references to this frame. */
-#define PGC_count_width PG_shift(9)
+#define PGC_count_width PG_shift(10)
#define PGC_count_mask ((1UL<<PGC_count_width)-1)
/*
diff --git a/xen/include/asm-x86/mm.h b/xen/include/asm-x86/mm.h
index 2ca8882ad0..06d64d494d 100644
--- a/xen/include/asm-x86/mm.h
+++ b/xen/include/asm-x86/mm.h
@@ -77,9 +77,12 @@
#define PGC_state_offlined PG_mask(2, 9)
#define PGC_state_free PG_mask(3, 9)
#define page_state_is(pg, st) (((pg)->count_info&PGC_state) == PGC_state_##st)
+/* Page is not reference counted */
+#define _PGC_extra PG_shift(10)
+#define PGC_extra PG_mask(1, 10)
- /* Count of references to this frame. */
-#define PGC_count_width PG_shift(9)
+/* Count of references to this frame. */
+#define PGC_count_width PG_shift(10)
#define PGC_count_mask ((1UL<<PGC_count_width)-1)
/*
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index 7c5c437247..763fcd56a4 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -361,15 +361,17 @@ struct domain
spinlock_t domain_lock;
- spinlock_t page_alloc_lock; /* protects all the following fields */
- struct page_list_head page_list; /* linked list */
+ spinlock_t page_alloc_lock; /* protects all the following fields */
+ struct page_list_head page_list; /* linked list */
struct page_list_head xenpage_list; /* linked list (size xenheap_pages) */
- unsigned int tot_pages; /* number of pages currently possesed */
- unsigned int xenheap_pages; /* # pages allocated from Xen heap */
- unsigned int outstanding_pages; /* pages claimed but not possessed */
- unsigned int max_pages; /* maximum value for tot_pages */
- atomic_t shr_pages; /* number of shared pages */
- atomic_t paged_pages; /* number of paged-out pages */
+ unsigned int tot_pages; /* number of pages currently possesed */
+ unsigned int xenheap_pages; /* number of pages from Xen heap */
+ unsigned int outstanding_pages; /* pages claimed but not possessed */
+ unsigned int extra_pages; /* extra pages not limited by max_pages */
+ unsigned int max_pages; /* maximum value for tot_pages minus */
+ /* extra_pages */
+ atomic_t shr_pages; /* number of shared pages */
+ atomic_t paged_pages; /* number of paged-out pages */
/* Scheduling. */
void *sched_priv; /* scheduler-specific data */
--
2.20.1
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^ permalink raw reply related [flat|nested] 9+ messages in thread
* [Xen-devel] [PATCH v7 3/3] x86 / vmx: use a MEMF_no_refcount domheap page for APIC_DEFAULT_PHYS_BASE
2020-01-29 17:10 [Xen-devel] [PATCH v7 0/3] purge free_shared_domheap_page() Paul Durrant
2020-01-29 17:10 ` [Xen-devel] [PATCH v7 1/3] x86 / vmx: move teardown from domain_destroy() Paul Durrant
2020-01-29 17:10 ` [Xen-devel] [PATCH v7 2/3] mm: make pages allocated with MEMF_no_refcount safe to assign Paul Durrant
@ 2020-01-29 17:10 ` Paul Durrant
2 siblings, 0 replies; 9+ messages in thread
From: Paul Durrant @ 2020-01-29 17:10 UTC (permalink / raw)
To: xen-devel
Cc: Kevin Tian, Wei Liu, Andrew Cooper, Paul Durrant, Jun Nakajima,
Roger Pau Monné
vmx_alloc_vlapic_mapping() currently contains some very odd looking code
that allocates a MEMF_no_owner domheap page and then shares with the guest
as if it were a xenheap page. This then requires vmx_free_vlapic_mapping()
to call a special function in the mm code: free_shared_domheap_page().
By using a MEMF_no_refcount domheap page instead, the odd looking code in
vmx_alloc_vlapic_mapping() can simply use get_page_and_type() to set up a
writable mapping before insertion in the P2M and vmx_free_vlapic_mapping()
can simply release the page using put_page_alloc_ref() followed by
put_page_and_type(). This then allows free_shared_domheap_page() to be
purged.
Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
---
Cc: Jun Nakajima <jun.nakajima@intel.com>
Cc: Kevin Tian <kevin.tian@intel.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Wei Liu <wl@xen.org>
Cc: "Roger Pau Monné" <roger.pau@citrix.com>
v4:
- Use a MEMF_no_refcount page rather than a 'normal' page
v2:
- Set an initial value for max_pages rather than avoiding the check in
assign_pages()
- Make domain_destroy() optional
---
xen/arch/x86/hvm/vmx/vmx.c | 21 ++++++++++++++++++---
xen/arch/x86/mm.c | 10 ----------
xen/include/asm-x86/mm.h | 2 --
3 files changed, 18 insertions(+), 15 deletions(-)
diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 606f3dc2eb..7423d2421b 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -3028,12 +3028,22 @@ static int vmx_alloc_vlapic_mapping(struct domain *d)
if ( !cpu_has_vmx_virtualize_apic_accesses )
return 0;
- pg = alloc_domheap_page(d, MEMF_no_owner);
+ pg = alloc_domheap_page(d, MEMF_no_refcount);
if ( !pg )
return -ENOMEM;
+
+ if ( !get_page_and_type(pg, d, PGT_writable_page) )
+ {
+ /*
+ * The domain can't possibly know about this page yet, so failure
+ * here is a clear indication of something fishy going on.
+ */
+ domain_crash(d);
+ return -ENODATA;
+ }
+
mfn = page_to_mfn(pg);
clear_domain_page(mfn);
- share_xen_page_with_guest(pg, d, SHARE_rw);
d->arch.hvm.vmx.apic_access_mfn = mfn;
return set_mmio_p2m_entry(d, paddr_to_pfn(APIC_DEFAULT_PHYS_BASE), mfn,
@@ -3047,7 +3057,12 @@ static void vmx_free_vlapic_mapping(struct domain *d)
d->arch.hvm.vmx.apic_access_mfn = _mfn(0);
if ( !mfn_eq(mfn, _mfn(0)) )
- free_shared_domheap_page(mfn_to_page(mfn));
+ {
+ struct page_info *pg = mfn_to_page(mfn);
+
+ put_page_alloc_ref(pg);
+ put_page_and_type(pg);
+ }
}
static void vmx_install_vlapic_mapping(struct vcpu *v)
diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 5b04db8c21..8b290ab3a2 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -496,16 +496,6 @@ void share_xen_page_with_guest(struct page_info *page, struct domain *d,
spin_unlock(&d->page_alloc_lock);
}
-void free_shared_domheap_page(struct page_info *page)
-{
- put_page_alloc_ref(page);
- if ( !test_and_clear_bit(_PGC_xen_heap, &page->count_info) )
- ASSERT_UNREACHABLE();
- page->u.inuse.type_info = 0;
- page_set_owner(page, NULL);
- free_domheap_page(page);
-}
-
void make_cr3(struct vcpu *v, mfn_t mfn)
{
struct domain *d = v->domain;
diff --git a/xen/include/asm-x86/mm.h b/xen/include/asm-x86/mm.h
index 06d64d494d..fafb3af46d 100644
--- a/xen/include/asm-x86/mm.h
+++ b/xen/include/asm-x86/mm.h
@@ -320,8 +320,6 @@ struct page_info
#define maddr_get_owner(ma) (page_get_owner(maddr_to_page((ma))))
-extern void free_shared_domheap_page(struct page_info *page);
-
#define frame_table ((struct page_info *)FRAMETABLE_VIRT_START)
extern unsigned long max_page;
extern unsigned long total_pages;
--
2.20.1
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^ permalink raw reply related [flat|nested] 9+ messages in thread
* Re: [Xen-devel] [PATCH v7 2/3] mm: make pages allocated with MEMF_no_refcount safe to assign
2020-01-29 17:10 ` [Xen-devel] [PATCH v7 2/3] mm: make pages allocated with MEMF_no_refcount safe to assign Paul Durrant
@ 2020-01-30 10:19 ` Jan Beulich
2020-01-30 10:40 ` Durrant, Paul
2020-01-30 11:02 ` Jan Beulich
1 sibling, 1 reply; 9+ messages in thread
From: Jan Beulich @ 2020-01-30 10:19 UTC (permalink / raw)
To: Paul Durrant
Cc: Stefano Stabellini, Julien Grall, Wei Liu, Konrad Rzeszutek Wilk,
George Dunlap, Andrew Cooper, Ian Jackson, xen-devel,
Volodymyr Babchuk, Roger Pau Monné
On 29.01.2020 18:10, Paul Durrant wrote:
> NOTE: steal_page() is also modified to decrement extra_pages in the case of
> a PGC_extra page being stolen from a domain.
I don't think stealing of such pages should be allowed. If anything,
the replacement page then again should be an "extra" one, which I
guess would be quite ugly to arrange for. But such "extra" pages
aren't supposed to be properly exposed (and hence played with) to
the domain in the first place.
> --- a/xen/common/page_alloc.c
> +++ b/xen/common/page_alloc.c
> @@ -2256,6 +2256,7 @@ int assign_pages(
> {
> int rc = 0;
> unsigned long i;
> + unsigned int extra_pages = 0;
>
> spin_lock(&d->page_alloc_lock);
>
> @@ -2267,13 +2268,19 @@ int assign_pages(
> goto out;
> }
>
> + for ( i = 0; i < (1 << order); i++ )
> + if ( pg[i].count_info & PGC_extra )
> + extra_pages++;
Perhaps assume (and maybe ASSERT()) that all pages in the batch
are the same in this regard? Then you could ...
> if ( !(memflags & MEMF_no_refcount) )
> {
> - if ( unlikely((d->tot_pages + (1 << order)) > d->max_pages) )
> + unsigned int max_pages = d->max_pages - d->extra_pages - extra_pages;
> +
> + if ( unlikely((d->tot_pages + (1 << order)) > max_pages) )
> {
> gprintk(XENLOG_INFO, "Over-allocation for domain %u: "
> "%u > %u\n", d->domain_id,
> - d->tot_pages + (1 << order), d->max_pages);
> + d->tot_pages + (1 << order), max_pages);
> rc = -E2BIG;
> goto out;
> }
> @@ -2282,13 +2289,17 @@ int assign_pages(
> get_knownalive_domain(d);
> }
>
> + d->extra_pages += extra_pages;
... arrange things like this, I think:
if ( pg[i].count_info & PGC_extra )
d->extra_pages += 1U << order;
else if ( !(memflags & MEMF_no_refcount) )
{
unsigned int max_pages = d->max_pages - d->extra_pages;
...
This would, afaict, then also eliminate the need to mask off
MEMF_no_refcount in alloc_domheap_pages(), ...
> for ( i = 0; i < (1 << order); i++ )
> {
> + unsigned long count_info = pg[i].count_info;
> +
> ASSERT(page_get_owner(&pg[i]) == NULL);
> - ASSERT(!pg[i].count_info);
> + ASSERT(!(count_info & ~PGC_extra));
... resulting in my prior comment on this one still applying.
Besides the changes you've made, what about the code handling
XENMEM_set_pod_target? What about p2m-pod.c? And
pv_shim_setup_dom()? I'm also not fully sure whether
getdomaininfo() shouldn't subtract extra_pages, but I think
this is the only way to avoid having an externally visible
effect. There may be more. Perhaps it's best to introduce a
domain_tot_pages() inline function returning the difference,
and us it almost everywhere where ->tot_pages is used right
now.
Jan
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^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [Xen-devel] [PATCH v7 2/3] mm: make pages allocated with MEMF_no_refcount safe to assign
2020-01-30 10:19 ` Jan Beulich
@ 2020-01-30 10:40 ` Durrant, Paul
0 siblings, 0 replies; 9+ messages in thread
From: Durrant, Paul @ 2020-01-30 10:40 UTC (permalink / raw)
To: Jan Beulich
Cc: Stefano Stabellini, Julien Grall, Wei Liu, Konrad Rzeszutek Wilk,
George Dunlap, Andrew Cooper, Ian Jackson, xen-devel,
Volodymyr Babchuk, Roger Pau Monné
> -----Original Message-----
> From: Jan Beulich <jbeulich@suse.com>
> Sent: 30 January 2020 10:20
> To: Durrant, Paul <pdurrant@amazon.co.uk>
> Cc: xen-devel@lists.xenproject.org; Andrew Cooper
> <andrew.cooper3@citrix.com>; George Dunlap <George.Dunlap@eu.citrix.com>;
> Ian Jackson <ian.jackson@eu.citrix.com>; Julien Grall <julien@xen.org>;
> Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>; Stefano Stabellini
> <sstabellini@kernel.org>; Wei Liu <wl@xen.org>; Volodymyr Babchuk
> <Volodymyr_Babchuk@epam.com>; Roger Pau Monné <roger.pau@citrix.com>
> Subject: Re: [PATCH v7 2/3] mm: make pages allocated with MEMF_no_refcount
> safe to assign
>
> On 29.01.2020 18:10, Paul Durrant wrote:
> > NOTE: steal_page() is also modified to decrement extra_pages in the case
> of
> > a PGC_extra page being stolen from a domain.
>
> I don't think stealing of such pages should be allowed. If anything,
> the replacement page then again should be an "extra" one, which I
> guess would be quite ugly to arrange for. But such "extra" pages
> aren't supposed to be properly exposed (and hence played with) to
> the domain in the first place.
>
> > --- a/xen/common/page_alloc.c
> > +++ b/xen/common/page_alloc.c
> > @@ -2256,6 +2256,7 @@ int assign_pages(
> > {
> > int rc = 0;
> > unsigned long i;
> > + unsigned int extra_pages = 0;
> >
> > spin_lock(&d->page_alloc_lock);
> >
> > @@ -2267,13 +2268,19 @@ int assign_pages(
> > goto out;
> > }
> >
> > + for ( i = 0; i < (1 << order); i++ )
> > + if ( pg[i].count_info & PGC_extra )
> > + extra_pages++;
>
> Perhaps assume (and maybe ASSERT()) that all pages in the batch
> are the same in this regard? Then you could ...
>
> > if ( !(memflags & MEMF_no_refcount) )
> > {
> > - if ( unlikely((d->tot_pages + (1 << order)) > d->max_pages) )
> > + unsigned int max_pages = d->max_pages - d->extra_pages -
> extra_pages;
> > +
> > + if ( unlikely((d->tot_pages + (1 << order)) > max_pages) )
> > {
> > gprintk(XENLOG_INFO, "Over-allocation for domain %u: "
> > "%u > %u\n", d->domain_id,
> > - d->tot_pages + (1 << order), d->max_pages);
> > + d->tot_pages + (1 << order), max_pages);
> > rc = -E2BIG;
> > goto out;
> > }
> > @@ -2282,13 +2289,17 @@ int assign_pages(
> > get_knownalive_domain(d);
> > }
> >
> > + d->extra_pages += extra_pages;
>
> ... arrange things like this, I think:
>
> if ( pg[i].count_info & PGC_extra )
> d->extra_pages += 1U << order;
> else if ( !(memflags & MEMF_no_refcount) )
> {
> unsigned int max_pages = d->max_pages - d->extra_pages;
> ...
>
> This would, afaict, then also eliminate the need to mask off
> MEMF_no_refcount in alloc_domheap_pages(), ...
>
>
> > for ( i = 0; i < (1 << order); i++ )
> > {
> > + unsigned long count_info = pg[i].count_info;
> > +
> > ASSERT(page_get_owner(&pg[i]) == NULL);
> > - ASSERT(!pg[i].count_info);
> > + ASSERT(!(count_info & ~PGC_extra));
>
> ... resulting in my prior comment on this one still applying.
>
> Besides the changes you've made, what about the code handling
> XENMEM_set_pod_target? What about p2m-pod.c? And
> pv_shim_setup_dom()? I'm also not fully sure whether
> getdomaininfo() shouldn't subtract extra_pages, but I think
> this is the only way to avoid having an externally visible
> effect. There may be more. Perhaps it's best to introduce a
> domain_tot_pages() inline function returning the difference,
> and us it almost everywhere where ->tot_pages is used right
> now.
This is getting very very complicated now, which makes me think that my original approach using a 'normal' page and setting an initial max_pages in domain_create() was a better approach.
Paul
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^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [Xen-devel] [PATCH v7 2/3] mm: make pages allocated with MEMF_no_refcount safe to assign
2020-01-29 17:10 ` [Xen-devel] [PATCH v7 2/3] mm: make pages allocated with MEMF_no_refcount safe to assign Paul Durrant
2020-01-30 10:19 ` Jan Beulich
@ 2020-01-30 11:02 ` Jan Beulich
2020-01-30 11:10 ` Durrant, Paul
1 sibling, 1 reply; 9+ messages in thread
From: Jan Beulich @ 2020-01-30 11:02 UTC (permalink / raw)
To: Paul Durrant
Cc: Stefano Stabellini, Julien Grall, Wei Liu, Konrad Rzeszutek Wilk,
George Dunlap, Andrew Cooper, Ian Jackson, xen-devel,
Volodymyr Babchuk, Roger Pau Monné
(replying from seeing your reply on the list archives, i.e.
threading lost/broken)
On 30.01.2020 10:40, Paul Durrant wrote:
> This is getting very very complicated now, which makes me think that my
> original approach using a 'normal' page and setting an initial max_pages in
> domain_create() was a better approach.
I don't think so, no. I also don't thing auditing all ->{max,tot}_pages
uses can be called "very very complicated". All I can say (again, I
think) is that there was a reason this APIC page thing was done the
way it was done. (It's another thing that this probably wasn't a
_good_ reason.)
Jan
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^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [Xen-devel] [PATCH v7 2/3] mm: make pages allocated with MEMF_no_refcount safe to assign
2020-01-30 11:02 ` Jan Beulich
@ 2020-01-30 11:10 ` Durrant, Paul
0 siblings, 0 replies; 9+ messages in thread
From: Durrant, Paul @ 2020-01-30 11:10 UTC (permalink / raw)
To: Jan Beulich
Cc: Stefano Stabellini, Julien Grall, Wei Liu, Konrad Rzeszutek Wilk,
George Dunlap, Andrew Cooper, Ian Jackson, xen-devel,
Volodymyr Babchuk, Roger Pau Monné
> -----Original Message-----
> From: Jan Beulich <jbeulich@suse.com>
> Sent: 30 January 2020 11:02
> To: Durrant, Paul <pdurrant@amazon.co.uk>
> Cc: xen-devel@lists.xenproject.org; Andrew Cooper
> <andrew.cooper3@citrix.com>; George Dunlap <George.Dunlap@eu.citrix.com>;
> Ian Jackson <ian.jackson@eu.citrix.com>; Julien Grall <julien@xen.org>;
> Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>; Stefano Stabellini
> <sstabellini@kernel.org>; Wei Liu <wl@xen.org>; Volodymyr Babchuk
> <Volodymyr_Babchuk@epam.com>; Roger Pau Monné <roger.pau@citrix.com>
> Subject: Re: [PATCH v7 2/3] mm: make pages allocated with MEMF_no_refcount
> safe to assign
>
> (replying from seeing your reply on the list archives, i.e.
> threading lost/broken)
>
> On 30.01.2020 10:40, Paul Durrant wrote:
> > This is getting very very complicated now, which makes me think that my
> > original approach using a 'normal' page and setting an initial max_pages
> in
> > domain_create() was a better approach.
>
> I don't think so, no. I also don't thing auditing all ->{max,tot}_pages
> uses can be called "very very complicated". All I can say (again, I
> think) is that there was a reason this APIC page thing was done the
> way it was done. (It's another thing that this probably wasn't a
> _good_ reason.)
>
I really want to get rid of shared xenheap pages though, so I will persist. I'll add the domain_tot_pages() helper as you suggest. I also agree that steal_page() ought not to encounter a PGC_extra page so I think I'll just make that an error case.
Paul
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^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [Xen-devel] [PATCH v7 1/3] x86 / vmx: move teardown from domain_destroy()...
2020-01-29 17:10 ` [Xen-devel] [PATCH v7 1/3] x86 / vmx: move teardown from domain_destroy() Paul Durrant
@ 2020-02-03 8:08 ` Tian, Kevin
0 siblings, 0 replies; 9+ messages in thread
From: Tian, Kevin @ 2020-02-03 8:08 UTC (permalink / raw)
To: Paul Durrant, xen-devel
Cc: Nakajima, Jun, Wei Liu, Andrew Cooper, George Dunlap,
Roger Pau Monné
> From: Paul Durrant <pdurrant@amazon.com>
> Sent: Thursday, January 30, 2020 1:10 AM
>
> ... to domain_relinquish_resources().
>
> The teardown code frees the APICv page. This does not need to be done late
> so do it in domain_relinquish_resources() rather than domain_destroy().
>
> Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
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^ permalink raw reply [flat|nested] 9+ messages in thread
end of thread, other threads:[~2020-02-03 8:08 UTC | newest]
Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-01-29 17:10 [Xen-devel] [PATCH v7 0/3] purge free_shared_domheap_page() Paul Durrant
2020-01-29 17:10 ` [Xen-devel] [PATCH v7 1/3] x86 / vmx: move teardown from domain_destroy() Paul Durrant
2020-02-03 8:08 ` Tian, Kevin
2020-01-29 17:10 ` [Xen-devel] [PATCH v7 2/3] mm: make pages allocated with MEMF_no_refcount safe to assign Paul Durrant
2020-01-30 10:19 ` Jan Beulich
2020-01-30 10:40 ` Durrant, Paul
2020-01-30 11:02 ` Jan Beulich
2020-01-30 11:10 ` Durrant, Paul
2020-01-29 17:10 ` [Xen-devel] [PATCH v7 3/3] x86 / vmx: use a MEMF_no_refcount domheap page for APIC_DEFAULT_PHYS_BASE Paul Durrant
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