Re: [PATCH] skip virtio fs cache section to enable NIC pass through

[Dev Audsin]

virtio-fs with DAX is currently not compatible with NIC Pass through. VM fails to boot when DAX  cache is enabled and SR-IOV VF is being attached. This patch solves the problem. Hencem DAX cache and SR-IOV VF are be attached together.

When a SR-IOV VF attaches to a qemu process, vfio will try to pin the entire DAX Window but it is empty when the guest boots and will fail.
A method to make VFIO and DAX to work together is to make vfio skip DAX cache.
Currently DAX cache need to be set to 0, for the SR-IOV VF to be attached to Kata containers.
Enabling both SR-IOV VF and DAX work together will potentially improve performance for workloads which are I/O and network intensive

On Mon, Apr 26, 2021 at 9:24 PM Dev Audsin <dev.devaqemu@gmail.com> wrote:

Signed-off-by: Dev Audsin <dev.devaqemu@gmail.com>
---
 hw/vfio/common.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 6ff1daa763..3af70238bd 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -541,7 +541,8 @@ static int vfio_host_win_del(VFIOContainer *container, hwaddr min_iova,

 static bool vfio_listener_skipped_section(MemoryRegionSection *section)
 {
-    return (!memory_region_is_ram(section->mr) &&
+    return (!strcmp(memory_region_name(section->mr), "virtio-fs-cache")) ||
+          (!memory_region_is_ram(section->mr) &&
             !memory_region_is_iommu(section->mr)) ||
            /*
             * Sizing an enabled 64-bit BAR can cause spurious mappings to
--
2.25.1