From 3073774e638ef18d222465fe92bfc8fccb90d288 Mon Sep 17 00:00:00 2001 From: Serhii Popovych Date: Mon, 4 Dec 2017 09:36:41 -0500 Subject: [PATCH] KVM: PPC: Book3S HV: Drop prepare_done from struct kvm_resize_hpt Currently the kvm_resize_hpt structure has two fields relevant to the state of an ongoing resize: 'prepare_done', which indicates whether the worker thread has completed or not, and 'error' which indicates whether it was successful or not. Since the success/failure isn't known until completion, this is confusingly redundant. This patch consolidates the information into just the 'error' value: -EBUSY indicates the worked is still in progress, other negative values indicate (completed) failure, 0 indicates successful completion. As a bonus this reduces size of struct kvm_resize_hpt by __alignof__(struct kvm_hpt_info) and saves few bytes of code. While there correct comment in struct kvm_resize_hpt which references a non-existent semaphore (leftover from an early draft). Assert with WARN_ON() in case of HPT allocation thread work runs more than once for resize request or resize_hpt_allocate() returns -EBUSY that is treated specially. Change comparison against zero to make checkpatch.pl happy. Cc: stable@vger.kernel.org # v4.10+ Signed-off-by: Serhii Popovych [dwg: Changed BUG_ON()s to WARN_ON()s and altered commit message for clarity] Signed-off-by: David Gibson Signed-off-by: Paul Mackerras --- arch/powerpc/kvm/book3s_64_mmu_hv.c | 46 ++++++++++++++++++----------- 1 file changed, 28 insertions(+), 18 deletions(-) diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c index 966097232d21..f5f2c6bf5856 100644 --- a/arch/powerpc/kvm/book3s_64_mmu_hv.c +++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c @@ -65,11 +65,17 @@ struct kvm_resize_hpt { u32 order; /* These fields protected by kvm->lock */ - int error; - bool prepare_done; - /* Private to the work thread, until prepare_done is true, - * then protected by kvm->resize_hpt_sem */ + /* Possible values and their usage: + * <0 an error occurred during allocation, + * -EBUSY allocation is in the progress, + * 0 allocation made successfuly. + */ + int error; + + /* Private to the work thread, until error != -EBUSY, + * then protected by kvm->lock. + */ struct kvm_hpt_info hpt; }; @@ -1433,15 +1439,23 @@ static void resize_hpt_prepare_work(struct work_struct *work) struct kvm *kvm = resize->kvm; int err; + if (WARN_ON(resize->error != -EBUSY)) + return; + resize_hpt_debug(resize, "resize_hpt_prepare_work(): order = %d\n", resize->order); err = resize_hpt_allocate(resize); + /* We have strict assumption about -EBUSY + * when preparing for HPT resize. + */ + if (WARN_ON(err == -EBUSY)) + err = -EINPROGRESS; + mutex_lock(&kvm->lock); resize->error = err; - resize->prepare_done = true; mutex_unlock(&kvm->lock); } @@ -1466,14 +1480,12 @@ long kvm_vm_ioctl_resize_hpt_prepare(struct kvm *kvm, if (resize) { if (resize->order == shift) { - /* Suitable resize in progress */ - if (resize->prepare_done) { - ret = resize->error; - if (ret != 0) - resize_hpt_release(kvm, resize); - } else { + /* Suitable resize in progress? */ + ret = resize->error; + if (ret == -EBUSY) ret = 100; /* estimated time in ms */ - } + else if (ret) + resize_hpt_release(kvm, resize); goto out; } @@ -1493,6 +1505,8 @@ long kvm_vm_ioctl_resize_hpt_prepare(struct kvm *kvm, ret = -ENOMEM; goto out; } + + resize->error = -EBUSY; resize->order = shift; resize->kvm = kvm; INIT_WORK(&resize->work, resize_hpt_prepare_work); @@ -1547,16 +1561,12 @@ long kvm_vm_ioctl_resize_hpt_commit(struct kvm *kvm, if (!resize || (resize->order != shift)) goto out; - ret = -EBUSY; - if (!resize->prepare_done) - goto out; - ret = resize->error; - if (ret != 0) + if (ret) goto out; ret = resize_hpt_rehash(resize); - if (ret != 0) + if (ret) goto out; resize_hpt_pivot(resize);