[Xen-changelog] [xen staging] vpci: fix deferral of long operations

[patchbot@xxxxxxx]

commit 3e568fa9e19ccefcfd0d3056cb80d0b15f2bf0f7
Author:     Roger Pau Monné <roger.pau@xxxxxxxxxx>
AuthorDate: Mon Nov 26 15:41:12 2018 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Nov 26 15:41:12 2018 +0100

    vpci: fix deferral of long operations
    
    Current logic to handle long running operations is flawed because it
    doesn't prevent the guest vcpu from running. Fix this by raising a
    scheduler softirq when preemption is required, so that the do_softirq
    call in the guest entry path performs a rescheduling. Also move the
    call to vpci_process_pending into handle_hvm_io_completion, together
    with the IOREQ code that handles pending IO instructions.
    
    Note that a scheduler softirq is also raised when the long running
    operation is queued in order to prevent the guest vcpu from resuming
    execution.
    
    Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Reviewed-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/hvm/ioreq.c  | 9 ++++++---
 xen/drivers/vpci/header.c | 6 ++++++
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/hvm/ioreq.c b/xen/arch/x86/hvm/ioreq.c
index a56d634f31..71f23227e6 100644
--- a/xen/arch/x86/hvm/ioreq.c
+++ b/xen/arch/x86/hvm/ioreq.c
@@ -85,9 +85,6 @@ bool hvm_io_pending(struct vcpu *v)
     struct hvm_ioreq_server *s;
     unsigned int id;
 
-    if ( has_vpci(d) && vpci_process_pending(v) )
-        return true;
-
     FOR_EACH_IOREQ_SERVER(d, id, s)
     {
         struct hvm_ioreq_vcpu *sv;
@@ -186,6 +183,12 @@ bool handle_hvm_io_completion(struct vcpu *v)
     enum hvm_io_completion io_completion;
     unsigned int id;
 
+    if ( has_vpci(d) && vpci_process_pending(v) )
+    {
+        raise_softirq(SCHEDULE_SOFTIRQ);
+        return false;
+    }
+
     FOR_EACH_IOREQ_SERVER(d, id, s)
     {
         struct hvm_ioreq_vcpu *sv;
diff --git a/xen/drivers/vpci/header.c b/xen/drivers/vpci/header.c
index 39dffb21fb..92c00b68aa 100644
--- a/xen/drivers/vpci/header.c
+++ b/xen/drivers/vpci/header.c
@@ -184,6 +184,12 @@ static void defer_map(struct domain *d, struct pci_dev 
*pdev,
     curr->vpci.mem = mem;
     curr->vpci.cmd = cmd;
     curr->vpci.rom_only = rom_only;
+    /*
+     * Raise a scheduler softirq in order to prevent the guest from resuming
+     * execution with pending mapping operations, to trigger the invocation
+     * of vpci_process_pending().
+     */
+    raise_softirq(SCHEDULE_SOFTIRQ);
 }
 
 static int modify_bars(const struct pci_dev *pdev, uint16_t cmd, bool rom_only)
--
generated by git-patchbot for /home/xen/git/xen.git#staging

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