Dear Stephen, The changes you suggested have been incorporated in the latest patch-set v10. Responses to comments inline.
Internal Use - Confidential > -----Original Message----- > From: Stephen Hemminger <[email protected]> > Sent: Tuesday, April 7, 2026 7:21 AM > To: Bathija, Pravin <[email protected]> > Cc: [email protected]; [email protected]; [email protected]; > [email protected] > Subject: Re: [PATCH v9 0/5] Support add/remove memory region and get-max- > slots > > > [EXTERNAL EMAIL] > > On Tue, 7 Apr 2026 08:06:31 +0000 > <[email protected]> wrote: > > > From: Pravin M Bathija <[email protected]> > > > > This is version v9 of the patchset and it incorporates the > > recommendations made by Stephen Hemminger. > > > > Changes made to patch 3/5 > > - Restored max_guest_pages initial value to hardcoded 8 instead of > > VHOST_MEMORY_MAX_NREGIONS, matching upstream semantics. > > > > Changes made to patch 4/5 > > - Added close(reg->fd) and reg->fd = -1 before goto close_msg_fds in the > > mmap failure path to fix fd leak after fd was moved from ctx->fds[0]. > > - Converted dev_invalidate_vrings from a plain function to a macro + > > implementation function pair, accepting message ID as a parameter so > > the static_assert reports the correct handler at each call site. > > - Updated dev_invalidate_vrings call in add_mem_reg to pass > > VHOST_USER_ADD_MEM_REG as message ID. > > - Updated dev_invalidate_vrings call in rem_mem_reg to pass > > VHOST_USER_ADD_MEM_REG as message ID. > > > > This implementation has been extensively tested by doing Read/Write > > I/O from multiple instances of fio + libblkio (front-end) talking to > > spdk/dpdk (back-end) based drives. Tested with qemu front-end talking > > to dpdk testpmd (back-end) performing add/removal of memory regions. > > Also tested post-copy live migration after doing add_memory_region. > > > > Version Log: > > Version v9 (Current version): Incorporate code review suggestions from > > Stephen Hemminger as described above. > > Version v8: Incorporate code review suggestions from Stephen Hemminger. > > rewrite async_dma_map_region function to iterate guest pages by host > > address range matching change function dev_invalidate_vrings to accept > > a double pointer to propagate pointer updates new function > > remove_guest_pages was added add_mem_reg error path was narrowed to > > only clean up the single failed region instead of destroting all > > existing regions Version v7: Incorporate code review suggestions from > > Maxime Coquelin. > > Add debug messages to vhost_postcopy_register function. > > Version v6: Added the enablement of this feature as a final patch in > > this patch-set and other code optimizations as suggested by Maxime > > Coquelin. > > Version v5: removed the patch that increased the number of memory > > regions from 8 to 128. This will be submitted as a separate feature at > > a later point after incorporating additional optimizations. Also > > includes code optimizations as suggested by Feng Cheng Wen. > > Version v4: code optimizations as suggested by Feng Cheng Wen. > > Version v3: code optimizations as suggested by Maxime Coquelin and > > Thomas Monjalon. > > Version v2: code optimizations as suggested by Maxime Coquelin. > > Version v1: Initial patch set. > > > > Pravin M Bathija (5): > > vhost: add user to mailmap and define to vhost hdr > > vhost_user: header defines for add/rem mem region > > vhost_user: support function defines for back-end > > vhost_user: Function defs for add/rem mem regions > > vhost_user: enable configure memory slots > > > > .mailmap | 1 + > > lib/vhost/rte_vhost.h | 4 + > > lib/vhost/vhost_user.c | 403 > > ++++++++++++++++++++++++++++++++++++----- > > lib/vhost/vhost_user.h | 10 + > > 4 files changed, 375 insertions(+), 43 deletions(-) > > > > AI review is mostly clean now. > > Patch series looks good overall. One issue in 4/5: > In rem_mem_reg, dev_invalidate_vrings (which calls > translate_ring_addresses) runs while the region being removed is still mapped. > Any vring address that resolves into that region will get a pointer that > becomes > invalid after the subsequent free_mem_region/munmap. Consider freeing the > region first so translate only sees surviving regions. > Thanks for catching that — moved dev_invalidate_vrings after free_mem_region and the array compaction so that translate_ring_addresses only sees surviving regions. > Also minor: the v9 cover letter changelog says rem_mem_reg passes > VHOST_USER_ADD_MEM_REG but the code correctly uses > VHOST_USER_REM_MEM_REG — just a typo in the changelog. Again good catch, made the edit to the cover letter.
