[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [xen staging-4.15] x86/pv-shim: correct ballooning down for compat guests
commit ddab5b1e001366258c0bfc7d5995b9d548e6042b Author: Igor Druzhinin <igor.druzhinin@xxxxxxxxxx> AuthorDate: Mon Oct 31 13:38:05 2022 +0100 Commit: Jan Beulich <jbeulich@xxxxxxxx> CommitDate: Mon Oct 31 13:38:05 2022 +0100 x86/pv-shim: correct ballooning down for compat guests The compat layer for multi-extent memory ops may need to split incoming requests. Since the guest handles in the interface structures may not be altered, it does so by leveraging do_memory_op()'s continuation handling: It hands on non-initial requests with a non-zero start extent, with the (native) handle suitably adjusted down. As a result do_memory_op() sees only the first of potentially several requests with start extent being zero. In order to be usable as overall result, the function accumulates args.nr_done, i.e. it initialized the field with the start extent. Therefore non-initial requests resulting from the split would pass too large a number into pv_shim_offline_memory(). Address that breakage by always calling pv_shim_offline_memory() regardless of current hypercall preemption status, with a suitably adjusted first argument. Note that this is correct also for the native guest case: We now simply "commit" what was completed right away, rather than at the end of a series of preemption/re-start cycles. In fact this improves overall preemption behavior: There's no longer a potentially big chunk of work done non-preemptively at the end of the last "iteration". Fixes: b2245acc60c3 ("xen/pvshim: memory hotplug") Signed-off-by: Igor Druzhinin <igor.druzhinin@xxxxxxxxxx> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx> Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> master commit: 1d7fbc535d1d37bdc2cc53ede360b0f6651f7de1 master date: 2022-10-28 15:49:33 +0200 --- xen/common/memory.c | 19 +++++++------------ 1 file changed, 7 insertions(+), 12 deletions(-) diff --git a/xen/common/memory.c b/xen/common/memory.c index 95b2b934e4..a958d94ac3 100644 --- a/xen/common/memory.c +++ b/xen/common/memory.c @@ -1407,22 +1407,17 @@ long do_memory_op(unsigned long cmd, XEN_GUEST_HANDLE_PARAM(void) arg) rc = args.nr_done; - if ( args.preempted ) - return hypercall_create_continuation( - __HYPERVISOR_memory_op, "lh", - op | (rc << MEMOP_EXTENT_SHIFT), arg); - #ifdef CONFIG_X86 if ( pv_shim && op == XENMEM_decrease_reservation ) - /* - * Only call pv_shim_offline_memory when the hypercall has - * finished. Note that nr_done is used to cope in case the - * hypercall has failed and only part of the extents where - * processed. - */ - pv_shim_offline_memory(args.nr_done, args.extent_order); + pv_shim_offline_memory(args.nr_done - start_extent, + args.extent_order); #endif + if ( args.preempted ) + return hypercall_create_continuation( + __HYPERVISOR_memory_op, "lh", + op | (rc << MEMOP_EXTENT_SHIFT), arg); + break; case XENMEM_exchange: -- generated by git-patchbot for /home/xen/git/xen.git#staging-4.15
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