[SLOF] [PATCH v2] pci: force minimum mem bar alignment of 64K for board-qemu

[Michael Roth]

This is needed to ensure VFIO passthrough devices are able to
offload MMIO accesses to KVM.

Cc: Segher Boessenkool <segher at kernel.crashing.org>
Cc: Nikunj A Dadhania <nikunj at linux.vnet.ibm.com>
Cc: David Gibson <david at gibson.dropbear.id.au>
Signed-off-by: Michael Roth <mdroth at linux.vnet.ibm.com>
---
v2:
  * default to 0 min-align instead of 64K (David)                                       
  * refactor assign-var* for readability (Segher)
  * add/utilize umax instead of max (Segher)
---
 board-qemu/slof/pci-phb.fs |  4 ++++
 slof/engine.in             |  1 +
 slof/fs/pci-properties.fs  | 38 ++++++++++++++++++++++++++++++--------
 slof/fs/pci-scan.fs        |  3 +++
 4 files changed, 38 insertions(+), 8 deletions(-)

diff --git a/board-qemu/slof/pci-phb.fs b/board-qemu/slof/pci-phb.fs
index 667514e..698bf5a 100644
--- a/board-qemu/slof/pci-phb.fs
+++ b/board-qemu/slof/pci-phb.fs
@@ -331,6 +331,10 @@ setup-puid
    my-puid TO puid                  \ Set current puid
    phb-parse-ranges
    1 TO pci-hotplug-enabled
+   s" qemu,mem-bar-min-align" get-node get-property 0= IF
+       decode-int TO pci-mem-bar-min-align
+       2drop
+   THEN
    s" qemu,phb-enumerated" get-node get-property 0<> IF
        1 0 (probe-pci-host-bridge)
    ELSE
diff --git a/slof/engine.in b/slof/engine.in
index 0344a38..549e409 100644
--- a/slof/engine.in
+++ b/slof/engine.in
@@ -145,6 +145,7 @@ col(D2/ >R U2/ R@ LIT(8*CELLSIZE-1) LSHIFT OR R> 2/)
 col(NEGATE 0 SWAP -)
 col(ABS DUP 0< 0BRANCH(1) NEGATE)
 col(MAX 2DUP < 0BRANCH(1) SWAP DROP)
+col(UMAX 2DUP U< 0BRANCH(1) SWAP DROP)
 col(MIN 2DUP > 0BRANCH(1) SWAP DROP)
 col(U* *)
 col(1+ 1 +)
diff --git a/slof/fs/pci-properties.fs b/slof/fs/pci-properties.fs
index 7faa714..e6fd843 100644
--- a/slof/fs/pci-properties.fs
+++ b/slof/fs/pci-properties.fs
@@ -91,17 +91,37 @@
 \ ***************************************************************************************
 \ align the current mem and set var to next mem
 \ align with a size of 0 returns 0 !!!
-: assign-var ( size var -- al-mem )
-        2dup @                          \ ( size var size cur-mem ) read current free mem
-        swap #aligned                   \ ( size var al-mem )       align the mem to the size
-        dup 2swap -rot +                \ ( al-mem var new-mem )    add size to aligned mem
-        swap !                          \ ( al-mem )                set variable to new mem
+: assign-var-align ( size align var -- al-mem )
+        dup >r @                        \ ( size align cur-mem )
+        swap #aligned                   \ ( size al-mem )
+        tuck +                          \ ( al-mem new-mem )
+        r> !                            \ ( al-mem )
+;
+
+: assign-var-min-align ( size min-align var -- al-mem )
+        >r over umax                    \ ( size align )
+        r> assign-var-align             \ ( al-mem )
 ;
 
 \ set bar to current free mem ( in variable ) and set variable to next free mem
 : assign-bar-value32 ( bar size var -- 4 )
         over IF                         \ IF size > 0
-                assign-var              \ | ( bar al-mem ) set variable to next mem
+                >r                      \ | ( bar size )
+                pci-mem-bar-min-align   \ | ( bar size min-align )
+                r> assign-var-min-align \ | ( bar al-mem ) set variable to next mem
+                swap rtas-config-l!     \ | ( -- )         set the bar to al-mem
+        ELSE                            \ ELSE
+                2drop drop              \ | clear stack
+        THEN                            \ FI
+        4                               \ size of the base-address-register
+;
+
+\ set bar to current free mem ( in variable ) and set variable to next free mem
+: assign-io-bar-value32 ( bar size var -- 4 )
+        over IF                         \ IF size > 0
+                >r                      \ | ( bar size )
+                dup                     \ | ( bar size size-align )
+                r> assign-var-align     \ | ( bar al-mem ) set variable to next mem
                 swap rtas-config-l!     \ | ( -- )         set the bar to al-mem
         ELSE                            \ ELSE
                 2drop drop              \ | clear stack
@@ -112,7 +132,9 @@
 \ set bar to current free mem ( in variable ) and set variable to next free mem
 : assign-bar-value64 ( bar size var -- 8 )
         over IF                         \ IF size > 0
-                assign-var              \ | ( bar al-mem ) set variable to next mem
+                >r                      \ | ( bar size )
+                pci-mem-bar-min-align   \ | ( bar size min-align )
+                r> assign-var-min-align \ | ( bar al-mem ) set variable to next mem
                 swap                    \ | ( al-mem addr ) calc config-addr of this bar
                 2dup rtas-config-l!     \ | ( al-mem addr ) set the Lower part of the bar to al-mem
                 4 + swap 20 rshift      \ | ( al-mem>>32 addr ) prepare the upper part of the al-mem
@@ -163,7 +185,7 @@
 : assign-io-bar ( bar-addr -- 4 )
         dup pci-bar-size-io             \ fetch size
         pci-next-io                     \ var to change
-        assign-bar-value32              \ and set it all
+        assign-io-bar-value32           \ and set it all
 ;
 
 \ Setup an Expansion ROM bar
diff --git a/slof/fs/pci-scan.fs b/slof/fs/pci-scan.fs
index a528c8e..bd8cc0d 100644
--- a/slof/fs/pci-scan.fs
+++ b/slof/fs/pci-scan.fs
@@ -24,6 +24,9 @@ VARIABLE pci-max-io
 VARIABLE pci-next-mem64           \ prefetchable 64-bit memory mapped
 VARIABLE pci-max-mem64
 
+\ 0 to default to natural alignment
+0 VALUE pci-mem-bar-min-align
+
 \ Counter of busses found
 0 VALUE pci-bus-number
 \ Counter of devices found
-- 
2.7.4