[Xen-changelog] [xen stable-4.12] pci: clear {host/guest}_maskall field on assign

[patchbot@xxxxxxx]

commit 2a8209fd87fb1ae8f5df68b2883f8fa6eac79cf0
Author:     Roger Pau Monné <roger.pau@xxxxxxxxxx>
AuthorDate: Fri Oct 25 11:43:06 2019 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Oct 25 11:43:06 2019 +0200

    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@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    Tested-by: Chao Gao <chao.gao@xxxxxxxxx>
    master commit: 575e18d54d19eda787f6477a4acd3c50f72751a9
    master date: 2019-10-10 10:59:27 +0200
---
 xen/arch/x86/msi.c            | 25 +++++++++++++++++++++++++
 xen/drivers/passthrough/pci.c |  5 +++++
 xen/include/asm-x86/msi.h     |  1 +
 3 files changed, 31 insertions(+)

diff --git a/xen/arch/x86/msi.c b/xen/arch/x86/msi.c
index 89e61160e9..49a1f9b3ce 100644
--- a/xen/arch/x86/msi.c
+++ b/xen/arch/x86/msi.c
@@ -1292,6 +1292,31 @@ 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 d7420bd8bf..301960e57e 100644
--- a/xen/drivers/passthrough/pci.c
+++ b/xen/drivers/passthrough/pci.c
@@ -1476,7 +1476,12 @@ 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 10387dce2e..d27a20774a 100644
--- 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 {
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.12

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