Upstream-Status: Backport Signed-off-by: Kai Kang From d1d35cf4ffb6a60a356193397919e83306d0bb74 Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Tue, 2 Jun 2015 15:07:01 +0000 Subject: xen/MSI: don't open-code pass-through of enable bit modifications Bug-Debian: http://bugs.debian.org/787547 Without this the actual XSA-131 fix would cause the enable bit to not get set anymore (due to the write back getting suppressed there based on the OR of emu_mask, ro_mask, and res_mask). Note that the fiddling with the enable bit shouldn't really be done by qemu, but making this work right (via libxc and the hypervisor) will require more extensive changes, which can be postponed until after the security issue got addressed. This is a preparatory patch for XSA-131. Signed-off-by: Jan Beulich Acked-by: Stefano Stabellini --- hw/xen/xen_pt_config_init.c | 10 ++-------- 1 file changed, 2 insertions(+), 8 deletions(-) diff --git a/hw/xen/xen_pt_config_init.c b/hw/xen/xen_pt_config_init.c index 68b8f22..436d0fd 100644 --- a/hw/xen/xen_pt_config_init.c +++ b/hw/xen/xen_pt_config_init.c @@ -1053,7 +1053,6 @@ static int xen_pt_msgctrl_reg_write(XenPCIPassthroughState *s, XenPTMSI *msi = s->msi; uint16_t writable_mask = 0; uint16_t throughable_mask = 0; - uint16_t raw_val; /* Currently no support for multi-vector */ if (*val & PCI_MSI_FLAGS_QSIZE) { @@ -1066,12 +1065,11 @@ static int xen_pt_msgctrl_reg_write(XenPCIPassthroughState *s, msi->flags |= cfg_entry->data & ~PCI_MSI_FLAGS_ENABLE; /* create value for writing to I/O device register */ - raw_val = *val; throughable_mask = ~reg->emu_mask & valid_mask; *val = XEN_PT_MERGE_VALUE(*val, dev_value, throughable_mask); /* update MSI */ - if (raw_val & PCI_MSI_FLAGS_ENABLE) { + if (*val & PCI_MSI_FLAGS_ENABLE) { /* setup MSI pirq for the first time */ if (!msi->initialized) { /* Init physical one */ @@ -1099,10 +1097,6 @@ static int xen_pt_msgctrl_reg_write(XenPCIPassthroughState *s, xen_pt_msi_disable(s); } - /* pass through MSI_ENABLE bit */ - *val &= ~PCI_MSI_FLAGS_ENABLE; - *val |= raw_val & PCI_MSI_FLAGS_ENABLE; - return 0; } @@ -1301,7 +1295,7 @@ static XenPTRegInfo xen_pt_emu_reg_msi[] = { .size = 2, .init_val = 0x0000, .ro_mask = 0xFF8E, - .emu_mask = 0x017F, + .emu_mask = 0x017E, .init = xen_pt_msgctrl_reg_init, .u.w.read = xen_pt_word_reg_read, .u.w.write = xen_pt_msgctrl_reg_write, -- 2.1.4