From 1b0e2f0b607e88feb57accc9521e9623b56ab7e2 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Corvin=20K=C3=B6hne?= Date: Fri, 15 Oct 2021 09:25:54 +0200 Subject: [PATCH] bhyve: ignore low bits of CFGADR Bhyve could emulate wrong PCI registers. In the best case, the guest reads wrong registers and the device driver would report some errors. In the worst case, the guest writes to wrong PCI registers and could brick hardware when using PCI passthrough. According to Intels specification, low bits of CFGADR should be ignored. Some OS like linux may rely on it. Otherwise, bhyve could emulate a wrong PCI register. E.g. If linux would like to read 2 bytes from offset 0x02, following would happen. linux: outl 0x80000002 at CFGADR inw at CFGDAT + 2 bhyve: cfgoff = 0x80000002 & 0xFF = 0x02 coff = cfgoff + (port - CFGDAT) = 0x02 + 0x02 = 0x04 Bhyve would emulate the register at offset 0x04 not 0x02. Reviewed By: #bhyve, grehan Differential Revision: https://reviews.freebsd.org/D31819 Sponsored by: Beckhoff Automation GmbH & Co. KG --- usr.sbin/bhyve/pci_emul.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/usr.sbin/bhyve/pci_emul.c b/usr.sbin/bhyve/pci_emul.c index 113ac5121238..fd18fdbdaeab 100644 --- a/usr.sbin/bhyve/pci_emul.c +++ b/usr.sbin/bhyve/pci_emul.c @@ -2018,7 +2018,7 @@ pci_emul_cfgaddr(struct vmctx *ctx, int vcpu, int in, int port, int bytes, } else { x = *eax; cfgenable = (x & CONF1_ENABLE) == CONF1_ENABLE; - cfgoff = x & PCI_REGMAX; + cfgoff = (x & PCI_REGMAX) & ~0x03; cfgfunc = (x >> 8) & PCI_FUNCMAX; cfgslot = (x >> 11) & PCI_SLOTMAX; cfgbus = (x >> 16) & PCI_BUSMAX;