Alex Bennée <alex.ben...@linaro.org> writes:
> The purpose of vhost_section is to identify RAM regions that need to
> be made available to a vhost client. However when running under TCG
> all RAM sections have DIRTY_MEMORY_CODE set which leads to problems
> down the line.
>
> Re-factor the code so:
>
> - steps are clearer to follow
> - reason for rejection is recorded in the trace point
> - we allow DIRTY_MEMORY_CODE when TCG is enabled
>
> We expand the comment to explain that kernel based vhost has specific
> support for migration tracking.
>
Hi, I tested this with virtio-fs in x86_64 and ppc64le. Both TCG and KVM
(just in case).
With this patch the call to vhost_set_mem_table succeeds and the device
is set up properly:
# mount -t virtiofs myfs /mnt
# ls /mnt <--- previously this would hang in TCG
a b
> Signed-off-by: Alex Bennée <alex.ben...@linaro.org>
> Cc: Michael S. Tsirkin <m...@redhat.com>
> Cc: Dr. David Alan Gilbert <dgilb...@redhat.com>
> Cc: Stefan Hajnoczi <stefa...@redhat.com>
>
Tested-by: Fabiano Rosas <faro...@linux.ibm.com>
> ---
> v2
> - drop enum, add trace_vhost_reject_section
> - return false at any fail point
> - unconditionally add DIRTY_MEMORY_CODE to handled cases
> - slightly re-word the explanatory comment and commit message
> ---
> hw/virtio/vhost.c | 55 ++++++++++++++++++++++++++++++------------
> hw/virtio/trace-events | 3 ++-
> 2 files changed, 41 insertions(+), 17 deletions(-)
>
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index aff98a0ede5..120c0cc747b 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -27,6 +27,7 @@
> #include "migration/blocker.h"
> #include "migration/qemu-file-types.h"
> #include "sysemu/dma.h"
> +#include "sysemu/tcg.h"
> #include "trace.h"
>
> /* enabled until disconnected backend stabilizes */
> @@ -403,26 +404,48 @@ static int vhost_verify_ring_mappings(struct vhost_dev
> *dev,
> return r;
> }
>
> +/*
> + * vhost_section: identify sections needed for vhost access
> + *
> + * We only care about RAM sections here (where virtqueue can live). If
> + * we find one we still allow the backend to potentially filter it out
> + * of our list.
> + */
> static bool vhost_section(struct vhost_dev *dev, MemoryRegionSection
> *section)
> {
> - bool result;
> - bool log_dirty = memory_region_get_dirty_log_mask(section->mr) &
> - ~(1 << DIRTY_MEMORY_MIGRATION);
> - result = memory_region_is_ram(section->mr) &&
> - !memory_region_is_rom(section->mr);
> -
> - /* Vhost doesn't handle any block which is doing dirty-tracking other
> - * than migration; this typically fires on VGA areas.
> - */
> - result &= !log_dirty;
> + MemoryRegion *mr = section->mr;
> +
> + if (memory_region_is_ram(mr) && !memory_region_is_rom(mr)) {
> + uint8_t dirty_mask = memory_region_get_dirty_log_mask(mr);
> + uint8_t handled_dirty;
> +
> + /*
> + * Kernel based vhost doesn't handle any block which is doing
> + * dirty-tracking other than migration for which it has
> + * specific logging support. However for TCG the kernel never
> + * gets involved anyway so we can also ignore it's
> + * self-modiying code detection flags.
> + */
> + handled_dirty = (1 << DIRTY_MEMORY_MIGRATION);
> + handled_dirty |= (1 << DIRTY_MEMORY_CODE);
>
> - if (result && dev->vhost_ops->vhost_backend_mem_section_filter) {
> - result &=
> - dev->vhost_ops->vhost_backend_mem_section_filter(dev, section);
> - }
> + if (dirty_mask & ~handled_dirty) {
> + trace_vhost_reject_section(mr->name, 1);
> + return false;
> + }
> +
> + if (dev->vhost_ops->vhost_backend_mem_section_filter &&
> + !dev->vhost_ops->vhost_backend_mem_section_filter(dev, section))
> {
> + trace_vhost_reject_section(mr->name, 2);
> + return false;
> + }
>
> - trace_vhost_section(section->mr->name, result);
> - return result;
> + trace_vhost_section(mr->name);
> + return true;
> + } else {
> + trace_vhost_reject_section(mr->name, 3);
> + return false;
> + }
> }
>
> static void vhost_begin(MemoryListener *listener)
> diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events
> index 84ecb85d445..22427126b97 100644
> --- a/hw/virtio/trace-events
> +++ b/hw/virtio/trace-events
> @@ -5,7 +5,8 @@ vhost_commit(bool started, bool changed) "Started: %d
> Changed: %d"
> vhost_region_add_section(const char *name, uint64_t gpa, uint64_t size,
> uint64_t host) "%s: 0x%"PRIx64"+0x%"PRIx64" @ 0x%"PRIx64
> vhost_region_add_section_merge(const char *name, uint64_t new_size, uint64_t
> gpa, uint64_t owr) "%s: size: 0x%"PRIx64 " gpa: 0x%"PRIx64 " owr: 0x%"PRIx64
> vhost_region_add_section_aligned(const char *name, uint64_t gpa, uint64_t
> size, uint64_t host) "%s: 0x%"PRIx64"+0x%"PRIx64" @ 0x%"PRIx64
> -vhost_section(const char *name, int r) "%s:%d"
> +vhost_section(const char *name) "%s"
> +vhost_reject_section(const char *name, int d) "%s:%d"
> vhost_iotlb_miss(void *dev, int step) "%p step %d"
>
> # vhost-user.c
