[src/trunk]: src/sys/dev/pci disable I/O or mem decode before probing BAR size.

[bouyer <bouyer%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/1fe8fa405b2e
branches:  trunk
changeset: 932343:1fe8fa405b2e
user:      bouyer <bouyer%NetBSD.org@localhost>
date:      Tue May 05 16:58:11 2020 +0000

description:
disable I/O or mem decode before probing BAR size.
Bar size is probed writing 0xffffffff to the BAR and reading back; but while
doing this the decoding address is not guaranteed to be valid and could have
side effect.

Xen PVH enforces disabling decoding before writing to a BAR.

Proposed on tech-kern@, got positive comments

diffstat:

 sys/dev/pci/pci_map.c |  41 +++++++++++++++++++++++++++++++++++++----
 1 files changed, 37 insertions(+), 4 deletions(-)

diffs (107 lines):

diff -r 2f4474954846 -r 1fe8fa405b2e sys/dev/pci/pci_map.c
--- a/sys/dev/pci/pci_map.c     Tue May 05 16:04:07 2020 +0000
+++ b/sys/dev/pci/pci_map.c     Tue May 05 16:58:11 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: pci_map.c,v 1.39 2019/12/02 17:13:13 riastradh Exp $   */
+/*     $NetBSD: pci_map.c,v 1.40 2020/05/05 16:58:11 bouyer Exp $      */
 
 /*-
  * Copyright (c) 1998, 2000 The NetBSD Foundation, Inc.
@@ -34,7 +34,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: pci_map.c,v 1.39 2019/12/02 17:13:13 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: pci_map.c,v 1.40 2020/05/05 16:58:11 bouyer Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -49,7 +49,7 @@
 pci_io_find(pci_chipset_tag_t pc, pcitag_t tag, int reg, pcireg_t type,
     bus_addr_t *basep, bus_size_t *sizep, int *flagsp)
 {
-       pcireg_t address, mask;
+       pcireg_t address, mask, csr;
        int s;
 
        if (reg < PCI_MAPREG_START ||
@@ -75,9 +75,18 @@
         */
        s = splhigh();
        address = pci_conf_read(pc, tag, reg);
+       /*
+        * Disable decoding via the command register before writing to the
+        * BAR register. Changing the decoding address to all-one is
+        * not a valid address and could have side effects.
+        */
+       csr = pci_conf_read(pc, tag, PCI_COMMAND_STATUS_REG);
+       pci_conf_write(pc, tag, PCI_COMMAND_STATUS_REG,
+           csr & ~PCI_COMMAND_IO_ENABLE) ;
        pci_conf_write(pc, tag, reg, 0xffffffff);
        mask = pci_conf_read(pc, tag, reg);
        pci_conf_write(pc, tag, reg, address);
+       pci_conf_write(pc, tag, PCI_COMMAND_STATUS_REG, csr);
        splx(s);
 
        if (PCI_MAPREG_TYPE(address) != PCI_MAPREG_TYPE_IO) {
@@ -107,6 +116,7 @@
        pcireg_t address, mask, address1 = 0, mask1 = 0xffffffff;
        uint64_t waddress, wmask;
        int s, is64bit, isrom;
+       pcireg_t csr;
 
        is64bit = (PCI_MAPREG_MEM_TYPE(type) == PCI_MAPREG_MEM_TYPE_64BIT);
        isrom = (reg == PCI_MAPREG_ROM);
@@ -138,6 +148,14 @@
         */
        s = splhigh();
        address = pci_conf_read(pc, tag, reg);
+       csr = pci_conf_read(pc, tag, PCI_COMMAND_STATUS_REG);
+       /*
+        * Disable decoding via the command register before writing to the
+        * BAR register. Changing the decoding address to all-one is
+        * not a valid address and could have side effects.
+        */
+       pci_conf_write(pc, tag, PCI_COMMAND_STATUS_REG,
+           csr & ~PCI_COMMAND_MEM_ENABLE) ;
        pci_conf_write(pc, tag, reg, 0xffffffff);
        mask = pci_conf_read(pc, tag, reg);
        pci_conf_write(pc, tag, reg, address);
@@ -149,6 +167,7 @@
                        pci_conf_write(pc, tag, reg + 4, address1);
                }
        }
+       pci_conf_write(pc, tag, PCI_COMMAND_STATUS_REG, csr);
        splx(s);
 
        if (!isrom) {
@@ -240,14 +259,28 @@
 int
 pci_mapreg_probe(pci_chipset_tag_t pc, pcitag_t tag, int reg, pcireg_t *typep)
 {
-       pcireg_t address, mask;
+       pcireg_t address, mask, csr;
        int s;
 
        s = splhigh();
        address = pci_conf_read(pc, tag, reg);
+       /*
+        * Disable decoding via the command register before writing to the
+        * BAR register. Changing the decoding address to all-one is
+        * not a valid address and could have side effects.
+        */
+       csr = pci_conf_read(pc, tag, PCI_COMMAND_STATUS_REG);
+       if (PCI_MAPREG_TYPE(address) == PCI_MAPREG_TYPE_IO) {
+               pci_conf_write(pc, tag, PCI_COMMAND_STATUS_REG,
+                   csr & ~PCI_COMMAND_IO_ENABLE);
+       } else {
+               pci_conf_write(pc, tag, PCI_COMMAND_STATUS_REG,
+                   csr & ~PCI_COMMAND_MEM_ENABLE);
+       }
        pci_conf_write(pc, tag, reg, 0xffffffff);
        mask = pci_conf_read(pc, tag, reg);
        pci_conf_write(pc, tag, reg, address);
+       pci_conf_write(pc, tag, PCI_COMMAND_STATUS_REG, csr);
        splx(s);
 
        if (mask == 0) /* unimplemented mapping register */