pci: clear {host/guest}_maskall field on assign

The current implementation of host_maskall makes it sticky across
assign and deassign calls, which means that once a guest forces Xen to
set host_maskall the maskall bit is not going to be cleared until a
call to PHYSDEVOP_prepare_msix is performed. Such call however
shouldn't be part of the normal flow when doing PCI passthrough, and
hence the flag needs to be cleared when assigning in order to prevent
host_maskall being carried over from previous assignations.

Note that the entry maskbit is reset when the msix capability is
initialized, and the guest_maskall field is also cleared so that the
hardware value matches Xen's internal state (hardware maskall =
host_maskall | guest_maskall).

Also note that doing the reset of host_maskall there would allow the
guest to reset such field by enabling and disabling MSIX, which is not
intended.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Tested-by: Chao Gao <chao.gao@intel.com>
master commit: 575e18d54d19eda787f6477a4acd3c50f72751a9
master date: 2019-10-10 10:59:27 +0200

diff --git a/xen/arch/x86/msi.c b/xen/arch/x86/msi.c
index a978fa5c299b7e534f660dc19b93cae82a56db18..2bec43e416b32ea25fdd6ce5c6e94c5531e06e8f 100644 (file)
--- a/xen/arch/x86/msi.c
+++ b/xen/arch/x86/msi.c
@@ -1268,6 +1268,31 @@ void pci_cleanup_msi(struct pci_dev *pdev)
     msi_free_irqs(pdev);
 }
 
+int pci_reset_msix_state(struct pci_dev *pdev)
+{
+    uint8_t slot = PCI_SLOT(pdev->devfn);
+    uint8_t func = PCI_FUNC(pdev->devfn);
+    unsigned int pos = pci_find_cap_offset(pdev->seg, pdev->bus, slot, func,
+                                           PCI_CAP_ID_MSIX);
+
+    ASSERT(pos);
+    /*
+     * Xen expects the device state to be the after reset one, and hence
+     * host_maskall = guest_maskall = false and all entries should have the
+     * mask bit set. Test that the maskall bit is not set, having it set could
+     * signal that the device hasn't been reset properly.
+     */
+    if ( pci_conf_read16(pdev->seg, pdev->bus, slot, func,
+                         msix_control_reg(pos)) &
+         PCI_MSIX_FLAGS_MASKALL )
+        return -EBUSY;
+
+    pdev->msix->host_maskall = false;
+    pdev->msix->guest_maskall = false;
+
+    return 0;
+}
+
 int pci_msi_conf_write_intercept(struct pci_dev *pdev, unsigned int reg,
                                  unsigned int size, uint32_t *data)
 {

diff --git a/xen/drivers/passthrough/pci.c b/xen/drivers/passthrough/pci.c
index 037aba7c9451df9cb21732ef458b646af3195667..f73123761df21ebf19f67a9bbf8b8f8cc209fc62 100644 (file)
--- a/xen/drivers/passthrough/pci.c
+++ b/xen/drivers/passthrough/pci.c
@@ -1440,7 +1440,12 @@ static int assign_device(struct domain *d, u16 seg, u8 bus, u8 devfn, u32 flag)
     }
 
     if ( pdev->msix )
+    {
+        rc = pci_reset_msix_state(pdev);
+        if ( rc )
+            goto done;
         msixtbl_init(d);
+    }
 
     pdev->fault.count = 0;
 

diff --git a/xen/include/asm-x86/msi.h b/xen/include/asm-x86/msi.h
index 10387dce2e97b7e2ca877d9fd185f294d3b8e08d..d27a20774ae973520de644e2f564d962d0b8fc3d 100644 (file)
--- a/xen/include/asm-x86/msi.h
+++ b/xen/include/asm-x86/msi.h
@@ -92,6 +92,7 @@ extern int __setup_msi_irq(struct irq_desc *, struct msi_desc *,
 extern void teardown_msi_irq(int irq);
 extern int msi_free_vector(struct msi_desc *entry);
 extern int pci_restore_msi_state(struct pci_dev *pdev);
+extern int pci_reset_msix_state(struct pci_dev *pdev);
 
 struct msi_desc {
        struct msi_attrib {