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| author | Paul Mackerras <paulus@samba.org> | 2015-11-03 08:03:30 +0300 |
|---|---|---|
| committer | Paul Mackerras <paulus@samba.org> | 2015-11-06 08:02:59 +0300 |
| commit | f74f2e2e26199f695ca3df94f29e9ab7cb707ea4 (patch) | |
| tree | 67bc4239089514a1fbaa1c07b1a2705cb28b4743 /arch/powerpc | |
| parent | cf29b21595b91eecce6ca69b0f92d60bca076ef0 (diff) | |
| download | linux-f74f2e2e26199f695ca3df94f29e9ab7cb707ea4.tar.xz | |
KVM: PPC: Book3S HV: Don't dynamically split core when already split
In static micro-threading modes, the dynamic micro-threading code
is supposed to be disabled, because subcores can't make independent
decisions about what micro-threading mode to put the core in - there is
only one micro-threading mode for the whole core. The code that
implements dynamic micro-threading checks for this, except that the
check was missed in one case. This means that it is possible for a
subcore in static 2-way micro-threading mode to try to put the core
into 4-way micro-threading mode, which usually leads to stuck CPUs,
spinlock lockups, and other stalls in the host.
The problem was in the can_split_piggybacked_subcores() function, which
should always return false if the system is in a static micro-threading
mode. This fixes the problem by making can_split_piggybacked_subcores()
use subcore_config_ok() for its checks, as subcore_config_ok() includes
the necessary check for the static micro-threading modes.
Credit to Gautham Shenoy for working out that the reason for the hangs
and stalls we were seeing was that we were trying to do dynamic 4-way
micro-threading while we were in static 2-way mode.
Fixes: b4deba5c41e9
Cc: vger@stable.kernel.org # v4.3
Signed-off-by: Paul Mackerras <paulus@samba.org>
Diffstat (limited to 'arch/powerpc')
| -rw-r--r-- | arch/powerpc/kvm/book3s_hv.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c index 228049786888..becad3ababe3 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -2060,7 +2060,7 @@ static bool can_split_piggybacked_subcores(struct core_info *cip) return false; n_subcores += (cip->subcore_threads[sub] - 1) >> 1; } - if (n_subcores > 3 || large_sub < 0) + if (large_sub < 0 || !subcore_config_ok(n_subcores + 1, 2)) return false; /* |