On Thu, 7 Jul 2016, Julien Grall wrote:
> The function flush_tlb is called to invalidate the TLBs for the current
> domain when the stage-2 page tables are modified.
>
> On ARMv8, the instruction "tlbi vmalle1is" (resp. "tlbi vmalle1") will
> invalidate stage 1 entries associated to the current VMID (see D4-1811 in
> ARM DDI 0487A.j).
>
> Given that an implementation is allowed to cache separately stage 1 and
> stage 2 translation (see D4.7.1), the instructions will not remove stage
> 2 entries when the translation is not combined in a single entry.
> This will result the TLBs to hold invalid entries and possibly multiple
> entries using the same VA.
>
> Use "tlbi vmalls12e1is" (resp. "tlbi vmalls12e1"), to flush both stage
> 1 and 2 entries when the domain p2m is changed.
>
> Also modify flush_tlb_local to invalidate stage 1 and 2 for the local
> TLBs. Note that this function is used in the instruction abort path
> before translating a GVA to a IPA. As far as I understand is to avoid a
> guest poisoning the DTLB when memacces is in use. We might be able to
> only invalidate stage 1 entries. However, I choose the safest way for now
> (i.e invalidating stage 1 and 2 entries). We would need to introduce a
> new set of helpers when we will want to restrict it.
>
> Signed-off-by: Julien Grall <julien.gr...@arm.com>
Thanks.
Reviewed-by: Stefano Stabellini <sstabell...@kernel.org>
I'll commit it shortly.
> --
> This would need to be backported on any version of Xen currently
> supported (IIRC think up to Xen 4.5).
>
> Without this patch, stage 2 TLBs won't be flushed if the TLBs
> cache intermediate translations entries (IPA -> PA).
>
> Changes in v2:
> - Fix instructions name in the commit message
> ---
> xen/include/asm-arm/arm64/flushtlb.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/xen/include/asm-arm/arm64/flushtlb.h
> b/xen/include/asm-arm/arm64/flushtlb.h
> index a73df92..942f2d3 100644
> --- a/xen/include/asm-arm/arm64/flushtlb.h
> +++ b/xen/include/asm-arm/arm64/flushtlb.h
> @@ -6,7 +6,7 @@ static inline void flush_tlb_local(void)
> {
> asm volatile(
> "dsb sy;"
> - "tlbi vmalle1;"
> + "tlbi vmalls12e1;"
> "dsb sy;"
> "isb;"
> : : : "memory");
> @@ -17,7 +17,7 @@ static inline void flush_tlb(void)
> {
> asm volatile(
> "dsb sy;"
> - "tlbi vmalle1is;"
> + "tlbi vmalls12e1is;"
> "dsb sy;"
> "isb;"
> : : : "memory");
> --
> 1.9.1
>
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