[PATCH 6/8] mm/pdx: Standardize region validation wrt pdx compression

[Alejandro Vallejo <alejandro.vallejo@cloud.com>]

Regions must be occasionally validated for pdx compression validity. That
is, whether any of the machine addresses spanning the region have a bit set
in the pdx "hole" (which is expected to always contain zeroes). There are
a few such tests through the code, and they all check for different things.

This patch replaces all such occurences with a call to a centralized
function that checks a region for validity.

Signed-off-by: Alejandro Vallejo <alejandro.vallejo@cloud.com>
---
 xen/arch/x86/x86_64/mm.c |  2 +-
 xen/common/efi/boot.c    |  6 +++---
 xen/common/pdx.c         | 13 +++++++++++--
 xen/include/xen/pdx.h    |  9 +++++++++
 4 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/xen/arch/x86/x86_64/mm.c b/xen/arch/x86/x86_64/mm.c
index 60db439af3..914e65c26c 100644
--- a/xen/arch/x86/x86_64/mm.c
+++ b/xen/arch/x86/x86_64/mm.c
@@ -1168,7 +1168,7 @@ static int mem_hotadd_check(unsigned long spfn, unsigned long epfn)
     if ( (spfn | epfn) & ((1UL << PAGETABLE_ORDER) - 1) )
         return 0;
 
-    if ( (spfn | epfn) & pfn_hole_mask )
+    if ( !pdx_is_region_compressible(spfn, epfn) )
         return 0;
 
     /* Make sure the new range is not present now */
diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c
index 24169b7b50..b098a8c030 100644
--- a/xen/common/efi/boot.c
+++ b/xen/common/efi/boot.c
@@ -14,6 +14,7 @@
 #include <xen/multiboot.h>
 #include <xen/param.h>
 #include <xen/pci_regs.h>
+#include <xen/pdx.h>
 #include <xen/pfn.h>
 #if EFI_PAGE_SIZE != PAGE_SIZE
 # error Cannot use xen/pfn.h here!
@@ -1647,7 +1648,7 @@ static bool __init cf_check ram_range_valid(unsigned long smfn, unsigned long em
 {
     unsigned long sz = pfn_to_pdx(emfn - 1) / PDX_GROUP_COUNT + 1;
 
-    return !(smfn & pfn_hole_mask) &&
+    return pdx_is_region_compressible(smfn, emfn) &&
            find_next_bit(pdx_group_valid, sz,
                          pfn_to_pdx(smfn) / PDX_GROUP_COUNT) < sz;
 }
@@ -1759,8 +1760,7 @@ void __init efi_init_memory(void)
             prot |= _PAGE_NX;
 
         if ( pfn_to_pdx(emfn - 1) < (DIRECTMAP_SIZE >> PAGE_SHIFT) &&
-             !(smfn & pfn_hole_mask) &&
-             !((smfn ^ (emfn - 1)) & ~pfn_pdx_bottom_mask) )
+             pdx_is_region_compressible(smfn, emfn))
         {
             if ( (unsigned long)mfn_to_virt(emfn - 1) >= HYPERVISOR_VIRT_END )
                 prot &= ~_PAGE_GLOBAL;
diff --git a/xen/common/pdx.c b/xen/common/pdx.c
index 99d4a90a50..72845e4bab 100644
--- a/xen/common/pdx.c
+++ b/xen/common/pdx.c
@@ -88,7 +88,7 @@ bool __mfn_valid(unsigned long mfn)
 }
 
 /* Sets all bits from the most-significant 1-bit down to the LSB */
-static uint64_t __init fill_mask(uint64_t mask)
+static uint64_t fill_mask(uint64_t mask)
 {
     while (mask & (mask + 1))
         mask |= mask + 1;
@@ -96,6 +96,15 @@ static uint64_t __init fill_mask(uint64_t mask)
     return mask;
 }
 
+bool pdx_is_region_compressible(unsigned long smfn, unsigned long emfn)
+{
+    uint64_t base = smfn << PAGE_SHIFT;
+    uint64_t len = (emfn - smfn) << PAGE_SHIFT;
+
+    return !(smfn & pfn_hole_mask) &&
+           !(pdx_region_mask(base, len) & ~ma_va_bottom_mask);
+}
+
 /* We don't want to compress the low MAX_ORDER bits of the addresses. */
 uint64_t __init pdx_init_mask(uint64_t base_addr)
 {
@@ -103,7 +112,7 @@ uint64_t __init pdx_init_mask(uint64_t base_addr)
                          (uint64_t)1 << (MAX_ORDER + PAGE_SHIFT)) - 1);
 }
 
-uint64_t __init pdx_region_mask(uint64_t base, uint64_t len)
+uint64_t pdx_region_mask(uint64_t base, uint64_t len)
 {
     /*
      * We say a bit "moves" in a range if there exist 2 addresses in that
diff --git a/xen/include/xen/pdx.h b/xen/include/xen/pdx.h
index f8ca0f5821..5378e664c2 100644
--- a/xen/include/xen/pdx.h
+++ b/xen/include/xen/pdx.h
@@ -77,6 +77,15 @@ extern unsigned long pfn_top_mask, ma_top_mask;
                          (sizeof(*frame_table) & -sizeof(*frame_table)))
 extern unsigned long pdx_group_valid[];
 
+/**
+ * Validate a region's compatibility with the current compression runtime
+ *
+ * @param smfn Start mfn
+ * @param emfn End mfn (non-inclusive)
+ * @return True iff the region can be used with the current compression
+ */
+bool pdx_is_region_compressible(unsigned long smfn, unsigned long emfn);
+
 /**
  * Calculates a mask covering "moving" bits of all addresses of a region
  *
-- 
2.34.1