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| author | Michael Kelley <mhklinux@outlook.com> | 2024-10-03 06:53:29 +0300 |
|---|---|---|
| committer | Wei Liu <wei.liu@kernel.org> | 2025-01-10 03:54:21 +0300 |
| commit | a7ae41cd808557c1d4e21c4295578fffcba0eb34 (patch) | |
| tree | 69b6747ee33789bb10ec74f3aa44cea407c21a57 | |
| parent | 962a4c7ea87884ed44ff48213f00cd5114c357e9 (diff) | |
| download | linux-a7ae41cd808557c1d4e21c4295578fffcba0eb34.tar.xz | |
x86/hyperv: Don't assume cpu_possible_mask is dense
Current code allocates the hv_vp_assist_page array with size
num_possible_cpus(). This code assumes cpu_possible_mask is dense,
which is not true in the general case per [1]. If cpu_possible_mask
is sparse, the array might be indexed by a value beyond the size of
the array.
However, the configurations that Hyper-V provides to guest VMs on x86
hardware, in combination with how x86 code assigns Linux CPU numbers,
*does* always produce a dense cpu_possible_mask. So the dense assumption
is not currently causing failures. But for robustness against future
changes in how cpu_possible_mask is populated, update the code to no
longer assume dense.
The correct approach is to allocate the array with size "nr_cpu_ids".
While this leaves unused array entries corresponding to holes in
cpu_possible_mask, the holes are assumed to be minimal and hence the
amount of memory wasted by unused entries is minimal.
[1] https://lore.kernel.org/lkml/SN6PR02MB4157210CC36B2593F8572E5ED4692@SN6PR02MB4157.namprd02.prod.outlook.com/
Signed-off-by: Michael Kelley <mhklinux@outlook.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20241003035333.49261-2-mhklinux@outlook.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <20241003035333.49261-2-mhklinux@outlook.com>
| -rw-r--r-- | arch/x86/hyperv/hv_init.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c index ba469d6b8250..f82d1aefaa8a 100644 --- a/arch/x86/hyperv/hv_init.c +++ b/arch/x86/hyperv/hv_init.c @@ -472,7 +472,7 @@ void __init hyperv_init(void) if (hv_isolation_type_tdx()) hv_vp_assist_page = NULL; else - hv_vp_assist_page = kcalloc(num_possible_cpus(), + hv_vp_assist_page = kcalloc(nr_cpu_ids, sizeof(*hv_vp_assist_page), GFP_KERNEL); if (!hv_vp_assist_page) { |