@@ -278,23 +278,21 @@ void __msi_set_enable(u16 seg, u8 bus, u8 slot, u8 func, int pos, int enable)
static void msi_set_enable(struct pci_dev *dev, int enable)
{
- int pos;
+ int pos = dev->msi_pos;
u16 seg = dev->seg;
u8 bus = dev->bus;
u8 slot = PCI_SLOT(dev->devfn);
u8 func = PCI_FUNC(dev->devfn);
- pos = pci_find_cap_offset(dev->sbdf, PCI_CAP_ID_MSI);
if ( pos )
__msi_set_enable(seg, bus, slot, func, pos, enable);
}
static void msix_set_enable(struct pci_dev *dev, int enable)
{
- int pos;
+ int pos = dev->msix_pos;
uint16_t control;
- pos = pci_find_cap_offset(dev->sbdf, PCI_CAP_ID_MSIX);
if ( pos )
{
control = pci_conf_read16(dev->sbdf, msix_control_reg(pos));
@@ -601,7 +599,7 @@ static int msi_capability_init(struct pci_dev *dev,
uint16_t control;
ASSERT_PDEV_LIST_IS_READ_LOCKED(dev->domain);
- pos = pci_find_cap_offset(dev->sbdf, PCI_CAP_ID_MSI);
+ pos = dev->msi_pos;
if ( !pos )
return -ENODEV;
control = pci_conf_read16(dev->sbdf, msi_control_reg(pos));
@@ -764,7 +762,7 @@ static int msix_capability_init(struct pci_dev *dev,
u8 slot = PCI_SLOT(dev->devfn);
u8 func = PCI_FUNC(dev->devfn);
bool maskall = msix->host_maskall, zap_on_error = false;
- unsigned int pos = pci_find_cap_offset(dev->sbdf, PCI_CAP_ID_MSIX);
+ unsigned int pos = dev->msix_pos;
if ( !pos )
return -ENODEV;
@@ -1133,11 +1131,13 @@ static void _pci_cleanup_msix(struct arch_msix *msix)
static void __pci_disable_msix(struct msi_desc *entry)
{
struct pci_dev *dev = entry->dev;
- unsigned int pos = pci_find_cap_offset(dev->sbdf, PCI_CAP_ID_MSIX);
+ unsigned int pos = dev->msix_pos;
u16 control = pci_conf_read16(dev->sbdf,
msix_control_reg(entry->msi_attrib.pos));
bool maskall = dev->msix->host_maskall;
+ ASSERT(pos);
+
if ( unlikely(!(control & PCI_MSIX_FLAGS_ENABLE)) )
{
dev->msix->host_maskall = 1;
@@ -1241,7 +1241,7 @@ void pci_cleanup_msi(struct pci_dev *pdev)
int pci_reset_msix_state(struct pci_dev *pdev)
{
- unsigned int pos = pci_find_cap_offset(pdev->sbdf, PCI_CAP_ID_MSIX);
+ unsigned int pos = pdev->msix_pos;
ASSERT(pos);
/*
@@ -1269,8 +1269,7 @@ int pci_msi_conf_write_intercept(struct pci_dev *pdev, unsigned int reg,
if ( pdev->msix )
{
entry = find_msi_entry(pdev, -1, PCI_CAP_ID_MSIX);
- pos = entry ? entry->msi_attrib.pos
- : pci_find_cap_offset(pdev->sbdf, PCI_CAP_ID_MSIX);
+ pos = entry ? entry->msi_attrib.pos : pdev->msix_pos;
ASSERT(pos);
if ( reg >= pos && reg < msix_pba_offset_reg(pos) + 4 )
@@ -29,6 +29,7 @@ int pdev_msi_init(struct pci_dev *pdev)
{
uint16_t ctrl = pci_conf_read16(pdev->sbdf, msi_control_reg(pos));
+ pdev->msi_pos = pos;
pdev->msi_maxvec = multi_msi_capable(ctrl);
}
@@ -41,6 +42,8 @@ int pdev_msi_init(struct pci_dev *pdev)
if ( !msix )
return -ENOMEM;
+ pdev->msix_pos = pos;
+
spin_lock_init(&msix->table_lock);
ctrl = pci_conf_read16(pdev->sbdf, msix_control_reg(pos));
@@ -195,7 +195,7 @@ static void cf_check mask_write(
static int cf_check init_msi(struct pci_dev *pdev)
{
- unsigned int pos = pci_find_cap_offset(pdev->sbdf, PCI_CAP_ID_MSI);
+ unsigned int pos = pdev->msi_pos;
uint16_t control;
int ret;
@@ -711,7 +711,7 @@ static int cf_check init_msix(struct pci_dev *pdev)
struct vpci_msix *msix;
int rc;
- msix_offset = pci_find_cap_offset(pdev->sbdf, PCI_CAP_ID_MSIX);
+ msix_offset = pdev->msix_pos;
if ( !msix_offset )
return 0;
@@ -113,6 +113,9 @@ struct pci_dev {
pci_sbdf_t sbdf;
};
+ unsigned int msi_pos;
+ unsigned int msix_pos;
+
uint8_t msi_maxvec;
uint8_t phantom_stride;
Dom0 normally informs Xen of PCI device removal via PHYSDEVOP_pci_device_remove, e.g. in response to SR-IOV disable or hot-unplug. We might find ourselves with stale pdevs if a buggy dom0 fails to report removal via PHYSDEVOP_pci_device_remove. In this case, attempts to access the config space of the stale pdevs would be invalid and return all 1s. Some possible conditions leading to this are: 1. Dom0 disables SR-IOV without reporting VF removal to Xen. The Linux SR-IOV subsystem normally reports VF removal when a PF driver disables SR-IOV. In case of a buggy dom0 SR-IOV subsystem, SR-IOV could become disabled with stale dangling VF pdevs in both dom0 Linux and Xen. 2. Dom0 reporting PF removal without reporting VF removal. During SR-IOV PF removal (hot-unplug), a buggy PF driver may fail to disable SR-IOV, thus failing to remove the VFs, leaving stale dangling VFs behind in both Xen and Linux. At least Linux warns in this case: [ 100.000000] 0000:01:00.0: driver left SR-IOV enabled after remove In either case, Xen is left with stale VF pdevs, risking invalid PCI config space accesses. When Xen is built with CONFIG_DEBUG=y, the following Xen crashes were observed when dom0 attempted to access the config space of a stale VF: (XEN) Assertion 'pos' failed at arch/x86/msi.c:1274 (XEN) ----[ Xen-4.20-unstable x86_64 debug=y Tainted: C ]---- ... (XEN) Xen call trace: (XEN) [<ffff82d040346834>] R pci_msi_conf_write_intercept+0xa2/0x1de (XEN) [<ffff82d04035d6b4>] F pci_conf_write_intercept+0x68/0x78 (XEN) [<ffff82d0403264e5>] F arch/x86/pv/emul-priv-op.c#pci_cfg_ok+0xa0/0x114 (XEN) [<ffff82d04032660e>] F arch/x86/pv/emul-priv-op.c#guest_io_write+0xb5/0x1c8 (XEN) [<ffff82d0403267bb>] F arch/x86/pv/emul-priv-op.c#write_io+0x9a/0xe0 (XEN) [<ffff82d04037c77a>] F x86_emulate+0x100e5/0x25f1e (XEN) [<ffff82d0403941a8>] F x86_emulate_wrapper+0x29/0x64 (XEN) [<ffff82d04032802b>] F pv_emulate_privileged_op+0x12e/0x217 (XEN) [<ffff82d040369f12>] F do_general_protection+0xc2/0x1b8 (XEN) [<ffff82d040201aa7>] F x86_64/entry.S#handle_exception_saved+0x2b/0x8c (XEN) Assertion 'pos' failed at arch/x86/msi.c:1246 (XEN) ----[ Xen-4.20-unstable x86_64 debug=y Tainted: C ]---- ... (XEN) Xen call trace: (XEN) [<ffff82d040346b0a>] R pci_reset_msix_state+0x47/0x50 (XEN) [<ffff82d040287eec>] F pdev_msix_assign+0x19/0x35 (XEN) [<ffff82d040286184>] F drivers/passthrough/pci.c#assign_device+0x181/0x471 (XEN) [<ffff82d040287c36>] F iommu_do_pci_domctl+0x248/0x2ec (XEN) [<ffff82d040284e1f>] F iommu_do_domctl+0x26/0x44 (XEN) [<ffff82d0402483b8>] F do_domctl+0x8c1/0x1660 (XEN) [<ffff82d04032977e>] F pv_hypercall+0x5ce/0x6af (XEN) [<ffff82d0402012d3>] F lstar_enter+0x143/0x150 These ASSERTs triggered because the MSI-X capability position can't be found for a stale pdev. Latch the capability positions of MSI and MSI-X during device init, and replace instances of pci_find_cap_offset(..., PCI_CAP_ID_MSI{,X}) with the stored value. Introduce one additional ASSERT, while the two existing ASSERTs in question continue to work as intended, even with a stale pdev. Fixes: 484d7c852e4f ("x86/MSI-X: track host and guest mask-all requests separately") Fixes: 575e18d54d19 ("pci: clear {host/guest}_maskall field on assign") Signed-off-by: Stewart Hildebrand <stewart.hildebrand@amd.com> --- v5->v6; * latch MSI/MSI-X capability position during device init v4->v5: * new patch, independent of the rest of the series * new approach to fixing the issue: don't rely on dom0 to report any sort of device removal; rather, fix the condition directly --- Instructions to reproduce Requires Xen with CONFIG_DEBUG=y Tested with Linux 6.11 1. Dom0 disables SR-IOV without reporting VF removal to Xen. * Hack the Linux SR-IOV subsystem to remove the call to pci_stop_and_remove_bus_device() in drivers/pci/iov.c:pci_iov_remove_virtfn(). * Enable SR-IOV, then disable SR-IOV echo 1 > /sys/bus/pci/devices/0000\:01\:00.0/sriov_numvfs echo 0 > /sys/bus/pci/devices/0000\:01\:00.0/sriov_numvfs * Now we have a stale VF. We can trigger the ASSERT either by unbinding the VF driver and issuing a reset... echo 0000\:01\:10.0 > /sys/bus/pci/devices/0000\:01\:10.0/driver/unbind echo 1 > /sys/bus/pci/devices/0000\:01\:10.0/reset ... or by doing xl pci-assignable-add xl pci-assignable-add 01:10.0 2. Dom0 reporting PF removal without reporting VF removal. * Hack your PF driver to leave SR-IOV enabled when removing the device * Enable SR-IOV echo 1 > /sys/bus/pci/devices/0000\:01\:00.0/sriov_numvfs * Unplug the PCI device (qemu) device_del mydev * Now we have a stale VF. We can trigger the ASSERT either by re-adding the PF device with SR-IOV disabled... echo 0000\:01\:10.0 > /sys/bus/pci/devices/0000\:01\:10.0/driver/unbind (qemu) device_add igb,id=mydev,bus=pcie.1,netdev=net1 ... or by reset / xl pci-assignable-add as above. --- xen/arch/x86/msi.c | 19 +++++++++---------- xen/drivers/passthrough/msi.c | 3 +++ xen/drivers/vpci/msi.c | 2 +- xen/drivers/vpci/msix.c | 2 +- xen/include/xen/pci.h | 3 +++ 5 files changed, 17 insertions(+), 12 deletions(-)