From 083b9bd7a1c526d57ec17b23dd6eca414e808886 Mon Sep 17 00:00:00 2001 From: Alex Bennée Date: Fri, 5 Jun 2020 16:49:25 +0100 Subject: hw/virtio/vhost: re-factor vhost-section and allow DIRTY_MEMORY_CODE MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 We expand the comment to explain that kernel based vhost has specific support for migration tracking. Signed-off-by: Alex Bennée Tested-by: Fabiano Rosas Cc: Michael S. Tsirkin Cc: Dr. David Alan Gilbert Cc: Stefan Hajnoczi Message-Id: <20200605154929.26910-11-alex.bennee@linaro.org> --- hw/virtio/vhost.c | 57 +++++++++++++++++++++++++++++++++++++++---------------- 1 file changed, 41 insertions(+), 16 deletions(-) (limited to 'hw/virtio/vhost.c') diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c index aff98a0ede..e3e2181290 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 +404,50 @@ 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 and guest + * internals accessed by virtio might 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. However a vhost-user + * client could still confuse a TCG guest if it re-writes + * executable memory that has already been translated. + */ + handled_dirty = (1 << DIRTY_MEMORY_MIGRATION) | + (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) -- cgit 1.4.1