[PATCH] kvm: arm64: correctly align nVHE percpu data
David Brazdil
dbrazdil at google.com
Mon Nov 16 04:24:57 EST 2020
Thanks Jamie
On Fri, Nov 13, 2020 at 03:04:06PM +0000, Jamie Iles wrote:
> The nVHE percpu data is partially linked but the nVHE linker script did
> not align the percpu section. The PERCPU_INPUT macro would then align
> the data to a page boundary:
>
> #define PERCPU_INPUT(cacheline) \
> __per_cpu_start = .; \
> *(.data..percpu..first) \
> . = ALIGN(PAGE_SIZE); \
> *(.data..percpu..page_aligned) \
> . = ALIGN(cacheline); \
> *(.data..percpu..read_mostly) \
> . = ALIGN(cacheline); \
> *(.data..percpu) \
> *(.data..percpu..shared_aligned) \
> PERCPU_DECRYPTED_SECTION \
> __per_cpu_end = .;
>
> but then when the final vmlinux linking happens the hypervisor percpu
> data is included after page alignment and so the offsets potentially
> don't match. On my build I saw that the .hyp.data..percpu section was
> at address 0x20 and then the percpu data would begin at 0x1000 (because
> of the page alignment in PERCPU_INPUT), but when linked into vmlinux,
> everything would be shifted down by 0x20 bytes.
>
> This manifests as one of the CPUs getting lost when running
> kvm-unit-tests or starting any VM and subsequent soft lockup on a Cortex
> A72 device.
>
> Fixes: 30c953911c43 ("kvm: arm64: Set up hyp percpu data for nVHE")
> Cc: David Brazdil <dbrazdil at google.com>
> Cc: Marc Zyngier <maz at kernel.org>
> Cc: Will Deacon <will at kernel.org>
Acked-by: David Brazdil <dbrazdil at google.com>
> Signed-off-by: Jamie Iles <jamie at nuviainc.com>
> ---
> v2: add clarifying commentary
>
> arch/arm64/kvm/hyp/nvhe/hyp.lds.S | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/arch/arm64/kvm/hyp/nvhe/hyp.lds.S b/arch/arm64/kvm/hyp/nvhe/hyp.lds.S
> index bb2d986ff696..a797abace13f 100644
> --- a/arch/arm64/kvm/hyp/nvhe/hyp.lds.S
> +++ b/arch/arm64/kvm/hyp/nvhe/hyp.lds.S
> @@ -13,6 +13,11 @@
>
> SECTIONS {
> HYP_SECTION(.text)
> + /*
> + * .hyp..data..percpu needs to be page aligned to maintain the same
> + * alignment for when linking into vmlinux.
> + */
> + . = ALIGN(PAGE_SIZE);
> HYP_SECTION_NAME(.data..percpu) : {
> PERCPU_INPUT(L1_CACHE_BYTES)
> }
> --
> 2.27.0
>
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