RE: [PATCH 0/4] Fix racing TLBI with ASID/VMID reallocation

[Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>]

> -----Original Message-----
> From: Will Deacon [mailto:will@kernel.org]
> Sent: 06 August 2021 12:31
> To: linux-arm-kernel@lists.infradead.org
> Cc: kernel-team@android.com; Will Deacon <will@kernel.org>; Catalin
> Marinas <catalin.marinas@arm.com>; Marc Zyngier <maz@kernel.org>; Jade
> Alglave <jade.alglave@arm.com>; Shameerali Kolothum Thodi
> <shameerali.kolothum.thodi@huawei.com>; kvmarm@lists.cs.columbia.edu;
> linux-arch@vger.kernel.org
> Subject: [PATCH 0/4] Fix racing TLBI with ASID/VMID reallocation
> 
> Hi all,
> 
> While reviewing Shameer's reworked VMID allocator [1] and discussing
> with Marc, we spotted a race between TLB invalidation (which typically
> takes an ASID or VMID argument) and reallocation of ASID/VMID for the
> context being targetted.
> 
> The first patch spells out an example with try_to_unmap_one() in a
> comment, which Catalin has kindly modelled in TLA+ at [2].
> 
> Although I'm posting all this together for ease of review, the intention
> is that the first patch will go via arm64 with the latter going via kvm.
> 
> Cheers,
> 
> Will
> 
> [1]
> https://lore.kernel.org/r/20210729104009.382-1-shameerali.kolothum.thodi
> @huawei.com
> [2]
> https://git.kernel.org/pub/scm/linux/kernel/git/cmarinas/kernel-tla.git/commi
> t/

Hi Catalin,

I am going through the ASID TLA+ model and in the above commit, it appears that the
different ASID check(=> ActiveAsid(c1) # ActiveAsid(c2)) for the Invariant
UniqueASIDActiveTask is now removed.

Just wondering why that is not relevant anymore?

Thanks,
Shameer

> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Jade Alglave <jade.alglave@arm.com>
> Cc: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
> Cc: <kvmarm@lists.cs.columbia.edu>
> Cc: <linux-arch@vger.kernel.org>
> 
> --->8
> 
> Marc Zyngier (3):
>   KVM: arm64: Move kern_hyp_va() usage in __load_guest_stage2() into the
>     callers
>   KVM: arm64: Convert the host S2 over to __load_guest_stage2()
>   KVM: arm64: Upgrade VMID accesses to {READ,WRITE}_ONCE
> 
> Will Deacon (1):
>   arm64: mm: Fix TLBI vs ASID rollover
> 
>  arch/arm64/include/asm/kvm_mmu.h              | 17 ++++++-----
>  arch/arm64/include/asm/mmu.h                  | 29
> ++++++++++++++++---
>  arch/arm64/include/asm/tlbflush.h             | 11 +++----
>  arch/arm64/kvm/arm.c                          |  2 +-
>  arch/arm64/kvm/hyp/include/nvhe/mem_protect.h |  2 +-
>  arch/arm64/kvm/hyp/nvhe/mem_protect.c         |  6 ++--
>  arch/arm64/kvm/hyp/nvhe/switch.c              |  4 ++-
>  arch/arm64/kvm/hyp/nvhe/tlb.c                 |  2 +-
>  arch/arm64/kvm/hyp/vhe/switch.c               |  2 +-
>  arch/arm64/kvm/hyp/vhe/tlb.c                  |  2 +-
>  arch/arm64/kvm/mmu.c                          |  2 +-
>  11 files changed, 52 insertions(+), 27 deletions(-)
> 
> --
> 2.32.0.605.g8dce9f2422-goog