This is a note to let you know that I've just added the patch titled
KVM: PPC: Book3S HV: Drop prepare_done from struct kvm_resize_hpt
to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-ppc-book3s-hv-drop-prepare_done-from-struct-kvm_resize_hpt.patch
and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 3073774e638ef18d222465fe92bfc8fccb90d288 Mon Sep 17 00:00:00 2001
From: Serhii Popovych <spopovyc@xxxxxxxxxx>
Date: Mon, 4 Dec 2017 09:36:41 -0500
Subject: KVM: PPC: Book3S HV: Drop prepare_done from struct kvm_resize_hpt
From: Serhii Popovych <spopovyc@xxxxxxxxxx>
commit 3073774e638ef18d222465fe92bfc8fccb90d288 upstream.
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.
Signed-off-by: Serhii Popovych <spopovyc@xxxxxxxxxx>
[dwg: Changed BUG_ON()s to WARN_ON()s and altered commit message for
clarity]
Signed-off-by: David Gibson <david@xxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Paul Mackerras <paulus@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/kvm/book3s_64_mmu_hv.c | 44 ++++++++++++++++++++++--------------
1 file changed, 27 insertions(+), 17 deletions(-)
--- 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 */
+
+ /* Possible values and their usage:
+ * <0 an error occurred during allocation,
+ * -EBUSY allocation is in the progress,
+ * 0 allocation made successfuly.
+ */
int error;
- bool prepare_done;
- /* Private to the work thread, until prepare_done is true,
- * then protected by kvm->resize_hpt_sem */
+ /* Private to the work thread, until error != -EBUSY,
+ * then protected by kvm->lock.
+ */
struct kvm_hpt_info hpt;
};
@@ -1444,15 +1450,23 @@ static void resize_hpt_prepare_work(stru
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);
}
@@ -1477,14 +1491,12 @@ long kvm_vm_ioctl_resize_hpt_prepare(str
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;
}
@@ -1504,6 +1516,8 @@ long kvm_vm_ioctl_resize_hpt_prepare(str
ret = -ENOMEM;
goto out;
}
+
+ resize->error = -EBUSY;
resize->order = shift;
resize->kvm = kvm;
INIT_WORK(&resize->work, resize_hpt_prepare_work);
@@ -1558,16 +1572,12 @@ long kvm_vm_ioctl_resize_hpt_commit(stru
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);
Patches currently in stable-queue which might be from spopovyc@xxxxxxxxxx are
queue-4.14/kvm-ppc-book3s-hv-drop-prepare_done-from-struct-kvm_resize_hpt.patch
queue-4.14/kvm-ppc-book3s-hv-fix-use-after-free-in-case-of-multiple-resize-requests.patch