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pci/pcie: don't assume cap id 0 is reserved 

VFIO actually wants to create a capability with ID == 0.
This is done to make guest drivers skip the given capability.
pcie_add_capability then trips up on this capability
when looking for end of capability list.

To support this use-case, it's easy enough to switch to
e.g. 0xffffffff for these comparisons - we can be sure
it will never match a 16-bit capability ID.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
This commit is contained in:
Michael S. Tsirkin 2017-02-15 22:37:45 +02:00
parent ad584d37f2
commit 4bb571d857
1 changed files with 7 additions and 4 deletions
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11
hw/pci/pcie.c
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@ -610,7 +610,8 @@ bool pcie_cap_is_arifwd_enabled(const PCIDevice *dev)
* uint16_t ext_cap_size
*/
static uint16_t pcie_find_capability_list(PCIDevice *dev, uint16_t cap_id,
/* Passing a cap_id value > 0xffff will return 0 and put end of list in prev */
static uint16_t pcie_find_capability_list(PCIDevice *dev, uint32_t cap_id,
uint16_t *prev_p)
{
uint16_t prev = 0;
@ -679,9 +680,11 @@ void pcie_add_capability(PCIDevice *dev,
} else {
uint16_t prev;
/* 0 is reserved cap id. use internally to find the last capability
in the linked list */
next = pcie_find_capability_list(dev, 0, &prev);
/*
* 0xffffffff is not a valid cap id (it's a 16 bit field). use
* internally to find the last capability in the linked list.
*/
next = pcie_find_capability_list(dev, 0xffffffff, &prev);
assert(prev >= PCI_CONFIG_SPACE_SIZE);
assert(next == 0);