From: Oleksandr Andrushchenko <[email protected]> Reset the command register when assigning a PCI device to a guest: according to the PCI spec the PCI_COMMAND register is typically all 0's after reset, but this might not be true for the guest as it needs to respect host's settings. For that reason, do not write 0 to the PCI_COMMAND register directly, but go through the corresponding emulation layer (cmd_write), which will take care about the actual bits written. Also, honor value of PCI_COMMAND_VGA_PALETTE value, which is set by firmware.
Signed-off-by: Oleksandr Andrushchenko <[email protected]> Signed-off-by: Volodymyr Babchuk <[email protected]> --- Since v9: - Honor PCI_COMMAND_VGA_PALETTE bit Since v6: - use cmd_write directly without introducing emulate_cmd_reg - update commit message with more description on all 0's in PCI_COMMAND Since v5: - updated commit message Since v1: - do not write 0 to the command register, but respect host settings. --- xen/drivers/vpci/header.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/xen/drivers/vpci/header.c b/xen/drivers/vpci/header.c index e351db4620..1d243eeaf9 100644 --- a/xen/drivers/vpci/header.c +++ b/xen/drivers/vpci/header.c @@ -762,6 +762,12 @@ static int cf_check init_bars(struct pci_dev *pdev) return -EOPNOTSUPP; } + /* Reset the command register for guests. We want to preserve only + * PCI_COMMAND_VGA_PALETTE as it is configured by firmware */ + cmd = pci_conf_read16(pdev->sbdf, PCI_COMMAND); + if ( !is_hwdom ) + cmd_write(pdev, PCI_COMMAND, cmd & PCI_COMMAND_VGA_PALETTE, header); + /* Setup a handler for the command register. */ if ( is_hwdom ) rc = vpci_add_register(pdev->vpci, vpci_hw_read16, cmd_write, PCI_COMMAND, @@ -776,7 +782,6 @@ static int cf_check init_bars(struct pci_dev *pdev) return 0; /* Disable memory decoding before sizing. */ - cmd = pci_conf_read16(pdev->sbdf, PCI_COMMAND); if ( cmd & PCI_COMMAND_MEMORY ) pci_conf_write16(pdev->sbdf, PCI_COMMAND, cmd & ~PCI_COMMAND_MEMORY); -- 2.41.0
