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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [xen master] xen/pdx: Make CONFIG_PDX_COMPRESSION a common Kconfig option
commit 141db3325bf2b4b7efabcd5cd3f90fc8245fc34b
Author: Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>
AuthorDate: Tue Aug 8 14:02:20 2023 +0100
Commit: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Wed Oct 18 15:44:31 2023 +0100
xen/pdx: Make CONFIG_PDX_COMPRESSION a common Kconfig option
Adds a new compile-time flag to allow disabling PDX compression and
compiles out compression-related code/data. It also shorts the pdx<->pfn
conversion macros and creates stubs for masking functions.
While at it, removes the old arch-defined CONFIG_HAS_PDX flag. Despite the
illusion of choice, it was not optional.
There are ARM and PPC platforms with sparse RAM banks - leave compression
active by default there. However, there are no known production x86 systems
with sparse RAM banks, so disable compression. RISC-V platforms are unknown
right now. These decisions can be revisited if our understanding changes.
Signed-off-by: Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>
Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Release-acked-by: Henry Wang <Henry.Wang@xxxxxxx>
---
xen/arch/arm/Kconfig | 1 -
xen/arch/ppc/Kconfig | 1 -
xen/arch/x86/Kconfig | 1 -
xen/arch/x86/domain.c | 19 +++++++++++++------
xen/common/Kconfig | 18 +++++++++++++++---
xen/common/Makefile | 2 +-
xen/common/pdx.c | 16 ++++++++++++----
xen/include/xen/pdx.h | 38 +++++++++++++++++++++++++++++++++++---
8 files changed, 76 insertions(+), 20 deletions(-)
diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
index 632dd9792e..2939db429b 100644
--- a/xen/arch/arm/Kconfig
+++ b/xen/arch/arm/Kconfig
@@ -14,7 +14,6 @@ config ARM
select HAS_ALTERNATIVE
select HAS_DEVICE_TREE
select HAS_PASSTHROUGH
- select HAS_PDX
select HAS_PMAP
select HAS_UBSAN
select IOMMU_FORCE_PT_SHARE
diff --git a/xen/arch/ppc/Kconfig b/xen/arch/ppc/Kconfig
index a6eae597af..ab116ffb2a 100644
--- a/xen/arch/ppc/Kconfig
+++ b/xen/arch/ppc/Kconfig
@@ -1,7 +1,6 @@
config PPC
def_bool y
select HAS_DEVICE_TREE
- select HAS_PDX
config PPC64
def_bool y
diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig
index 92f3a627da..30df085d96 100644
--- a/xen/arch/x86/Kconfig
+++ b/xen/arch/x86/Kconfig
@@ -24,7 +24,6 @@ config X86
select HAS_PASSTHROUGH
select HAS_PCI
select HAS_PCI_MSI
- select HAS_PDX
select HAS_SCHED_GRANULARITY
select HAS_UBSAN
select HAS_VPCI if HVM
diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index d05ee0da55..3712e36df9 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -458,7 +458,7 @@ void domain_cpu_policy_changed(struct domain *d)
}
}
-#ifndef CONFIG_BIGMEM
+#if !defined(CONFIG_BIGMEM) && defined(CONFIG_PDX_COMPRESSION)
/*
* The hole may be at or above the 44-bit boundary, so we need to determine
* the total bit count until reaching 32 significant (not squashed out) bits
@@ -485,13 +485,20 @@ static unsigned int __init noinline
_domain_struct_bits(void)
struct domain *alloc_domain_struct(void)
{
struct domain *d;
-#ifdef CONFIG_BIGMEM
- const unsigned int bits = 0;
-#else
+
/*
- * We pack the PDX of the domain structure into a 32-bit field within
- * the page_info structure. Hence the MEMF_bits() restriction.
+ * Without CONFIG_BIGMEM, we pack the PDX of the domain structure into
+ * a 32-bit field within the page_info structure. Hence the MEMF_bits()
+ * restriction. With PDX compression in place the number of bits must
+ * be calculated at runtime, but it's fixed otherwise.
+ *
+ * On systems with CONFIG_BIGMEM there's no packing, and so there's no
+ * such restriction.
*/
+#if defined(CONFIG_BIGMEM) || !defined(CONFIG_PDX_COMPRESSION)
+ const unsigned int bits = IS_ENABLED(CONFIG_BIGMEM) ? 0 :
+ 32 + PAGE_SHIFT;
+#else
static unsigned int __read_mostly bits;
if ( unlikely(!bits) )
diff --git a/xen/common/Kconfig b/xen/common/Kconfig
index 0d248ab941..407b7b1cd6 100644
--- a/xen/common/Kconfig
+++ b/xen/common/Kconfig
@@ -23,6 +23,21 @@ config GRANT_TABLE
If unsure, say Y.
+config PDX_COMPRESSION
+ bool "PDX (Page inDeX) compression" if EXPERT && !X86 && !RISCV
+ default ARM || PPC
+ help
+ PDX compression is a technique designed to reduce the memory
+ overhead of physical memory management on platforms with sparse RAM
+ banks.
+
+ If your platform does have sparse RAM banks, enabling PDX
+ compression may reduce the memory overhead of Xen, but does carry a
+ runtime performance cost.
+
+ If your platform does not have sparse RAM banks, do not enable PDX
+ compression.
+
config ALTERNATIVE_CALL
bool
@@ -53,9 +68,6 @@ config HAS_IOPORTS
config HAS_KEXEC
bool
-config HAS_PDX
- bool
-
config HAS_PMAP
bool
diff --git a/xen/common/Makefile b/xen/common/Makefile
index e7e96b1087..69d6aa626c 100644
--- a/xen/common/Makefile
+++ b/xen/common/Makefile
@@ -30,7 +30,7 @@ obj-y += multicall.o
obj-y += notifier.o
obj-$(CONFIG_NUMA) += numa.o
obj-y += page_alloc.o
-obj-$(CONFIG_HAS_PDX) += pdx.o
+obj-y += pdx.o
obj-$(CONFIG_PERF_COUNTERS) += perfc.o
obj-bin-$(CONFIG_HAS_PMAP) += pmap.init.o
obj-y += preempt.o
diff --git a/xen/common/pdx.c b/xen/common/pdx.c
index d3d38965bd..d3d63b0750 100644
--- a/xen/common/pdx.c
+++ b/xen/common/pdx.c
@@ -31,11 +31,16 @@ unsigned long __read_mostly pdx_group_valid[BITS_TO_LONGS(
bool __mfn_valid(unsigned long mfn)
{
- if ( unlikely(evaluate_nospec(mfn >= max_page)) )
+ bool invalid = mfn >= max_page;
+
+#ifdef CONFIG_PDX_COMPRESSION
+ invalid |= mfn & pfn_hole_mask;
+#endif
+
+ if ( unlikely(evaluate_nospec(invalid)) )
return false;
- return likely(!(mfn & pfn_hole_mask)) &&
- likely(test_bit(pfn_to_pdx(mfn) / PDX_GROUP_COUNT,
- pdx_group_valid));
+
+ return test_bit(pfn_to_pdx(mfn) / PDX_GROUP_COUNT, pdx_group_valid);
}
void set_pdx_range(unsigned long smfn, unsigned long emfn)
@@ -49,6 +54,8 @@ void set_pdx_range(unsigned long smfn, unsigned long emfn)
__set_bit(idx, pdx_group_valid);
}
+#ifdef CONFIG_PDX_COMPRESSION
+
/*
* Diagram to make sense of the following variables. The masks and shifts
* are done on mfn values in order to convert to/from pdx:
@@ -176,6 +183,7 @@ void __init pfn_pdx_hole_setup(unsigned long mask)
ma_top_mask = pfn_top_mask << PAGE_SHIFT;
}
+#endif /* CONFIG_PDX_COMPRESSION */
/*
* Local variables:
diff --git a/xen/include/xen/pdx.h b/xen/include/xen/pdx.h
index f3fbc4273a..bd535009ea 100644
--- a/xen/include/xen/pdx.h
+++ b/xen/include/xen/pdx.h
@@ -67,8 +67,6 @@
* region involved.
*/
-#ifdef CONFIG_HAS_PDX
-
extern unsigned long max_pdx;
#define PDX_GROUP_COUNT ((1 << PDX_GROUP_SHIFT) / \
@@ -100,6 +98,8 @@ bool __mfn_valid(unsigned long mfn);
#define mfn_to_pdx(mfn) pfn_to_pdx(mfn_x(mfn))
#define pdx_to_mfn(pdx) _mfn(pdx_to_pfn(pdx))
+#ifdef CONFIG_PDX_COMPRESSION
+
extern unsigned long pfn_pdx_bottom_mask, ma_va_bottom_mask;
extern unsigned int pfn_pdx_hole_shift;
extern unsigned long pfn_hole_mask;
@@ -206,7 +206,39 @@ static inline paddr_t directmapoff_to_maddr(unsigned long
offset)
*/
void pfn_pdx_hole_setup(unsigned long mask);
-#endif /* HAS_PDX */
+#else /* !CONFIG_PDX_COMPRESSION */
+
+/* Without PDX compression we can skip some computations */
+
+/* pdx<->pfn == identity */
+#define pdx_to_pfn(x) (x)
+#define pfn_to_pdx(x) (x)
+
+/* directmap is indexed by by maddr */
+#define maddr_to_directmapoff(x) (x)
+#define directmapoff_to_maddr(x) (x)
+
+static inline bool pdx_is_region_compressible(paddr_t base,
+ unsigned long npages)
+{
+ return true;
+}
+
+static inline uint64_t pdx_init_mask(uint64_t base_addr)
+{
+ return 0;
+}
+
+static inline uint64_t pdx_region_mask(uint64_t base, uint64_t len)
+{
+ return 0;
+}
+
+static inline void pfn_pdx_hole_setup(unsigned long mask)
+{
+}
+
+#endif /* CONFIG_PDX_COMPRESSION */
#endif /* __XEN_PDX_H__ */
/*
--
generated by git-patchbot for /home/xen/git/xen.git#master
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