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Allow a 4-byte write to PCI config space to overlap

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the 2 read-only bytes at the start of a PCI capability.
This is the sequence that OpenBSD uses when enabling
MSI interrupts, and works fine on real h/w.

In bhyve, convert the 4 byte write to a 2-byte write to
the r/w area past the first 2 r/o bytes of a capability.

Reviewed by:	neel
Approved by:	re@ (blanket)
This commit is contained in:
Peter Grehan 2013-10-09 23:53:21 +00:00
parent d5cc57e6ab
commit 2a8d400a2e
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=256248
1 changed files with 12 additions and 3 deletions
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15
usr.sbin/bhyve/pci_emul.c
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@ -941,10 +941,19 @@ pci_emul_capwrite(struct pci_devinst *pi, int offset, int bytes, uint32_t val)
assert(offset >= capoff);
/*
* Capability ID and Next Capability Pointer are readonly
* Capability ID and Next Capability Pointer are readonly.
* However, some o/s's do 4-byte writes that include these.
* For this case, trim the write back to 2 bytes and adjust
* the data.
*/
if (offset == capoff || offset == capoff + 1)
return;
if (offset == capoff || offset == capoff + 1) {
if (offset == capoff && bytes == 4) {
bytes = 2;
offset += 2;
val >>= 16;
} else
return;
}
switch (capid) {
case PCIY_MSI: