Dear Stephen, I wanted to check-in about the v10 patch-set if there are items that need attention. Also since there are SPDK and other open-source storage patches that are dependent on this feature, it would be great to have this merged soon, if everything looks good.
Regards, Pravin Internal Use - Confidential > -----Original Message----- > From: Bathija, Pravin > Sent: Tuesday, April 7, 2026 3:44 PM > To: 'Stephen Hemminger' <[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 > > Dear Stephen, > > The changes you suggested have been incorporated in the latest patch-set v10. > Responses to comments inline. > > > -----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.
