[PATCH 1/2] x86/msi: passthrough all MSI-X vector ctrl writes to device model

[Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>]

QEMU needs to know whether clearing maskbit of a vector is really
clearing, or was already cleared before. Currently Xen sends only
clearing that bit to the device model, but not setting it, so QEMU
cannot detect it. Because of that, QEMU is working this around by
checking via /dev/mem, but that isn't the proper approach.

Give all necessary information to QEMU by passing all ctrl writes,
including masking a vector.

Signed-off-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
---
 xen/arch/x86/hvm/vmsi.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/hvm/vmsi.c b/xen/arch/x86/hvm/vmsi.c
index 75f92885dc5e..ba4cf46dfe91 100644
--- a/xen/arch/x86/hvm/vmsi.c
+++ b/xen/arch/x86/hvm/vmsi.c
@@ -271,7 +271,8 @@ out:
 }
 
 static int msixtbl_write(struct vcpu *v, unsigned long address,
-                         unsigned int len, unsigned long val)
+                         unsigned int len, unsigned long val,
+                         bool completion)
 {
     unsigned long offset;
     struct msixtbl_entry *entry;
@@ -343,7 +344,7 @@ static int msixtbl_write(struct vcpu *v, unsigned long 
address,
 
 unlock:
     spin_unlock_irqrestore(&desc->lock, flags);
-    if ( len == 4 )
+    if ( len == 4 && completion )
         r = X86EMUL_OKAY;
 
 out:
@@ -355,7 +356,7 @@ static int cf_check _msixtbl_write(
     const struct hvm_io_handler *handler, uint64_t address, uint32_t len,
     uint64_t val)
 {
-    return msixtbl_write(current, address, len, val);
+    return msixtbl_write(current, address, len, val, false);
 }
 
 static bool cf_check msixtbl_range(
@@ -633,7 +634,7 @@ void msix_write_completion(struct vcpu *v)
         return;
 
     v->arch.hvm.hvm_io.msix_unmask_address = 0;
-    if ( msixtbl_write(v, ctrl_address, 4, 0) != X86EMUL_OKAY )
+    if ( msixtbl_write(v, ctrl_address, 4, 0, true) != X86EMUL_OKAY )
         gdprintk(XENLOG_WARNING, "MSI-X write completion failure\n");
 }
 
-- 
2.37.3