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    Subject[PATCH v5 04/17] arm64: Don't trap host pointer auth use to EL2
    Date
    From: Mark Rutland <mark.rutland@arm.com>

    To allow EL0 (and/or EL1) to use pointer authentication functionality,
    we must ensure that pointer authentication instructions and accesses to
    pointer authentication keys are not trapped to EL2.

    This patch ensures that HCR_EL2 is configured appropriately when the
    kernel is booted at EL2. For non-VHE kernels we set HCR_EL2.{API,APK},
    ensuring that EL1 can access keys and permit EL0 use of instructions.
    For VHE kernels host EL0 (TGE && E2H) is unaffected by these settings,
    and it doesn't matter how we configure HCR_EL2.{API,APK}, so we don't
    bother setting them.

    This does not enable support for KVM guests, since KVM manages HCR_EL2
    itself when running VMs.

    Signed-off-by: Mark Rutland <mark.rutland@arm.com>
    Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
    Acked-by: Christoffer Dall <christoffer.dall@arm.com>
    Cc: Catalin Marinas <catalin.marinas@arm.com>
    Cc: Marc Zyngier <marc.zyngier@arm.com>
    Cc: Will Deacon <will.deacon@arm.com>
    Cc: kvmarm@lists.cs.columbia.edu
    ---
    arch/arm64/include/asm/kvm_arm.h | 4 +++-
    1 file changed, 3 insertions(+), 1 deletion(-)

    diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
    index f885f4e96002..1405bb24acac 100644
    --- a/arch/arm64/include/asm/kvm_arm.h
    +++ b/arch/arm64/include/asm/kvm_arm.h
    @@ -24,6 +24,8 @@

    /* Hyp Configuration Register (HCR) bits */
    #define HCR_FWB (UL(1) << 46)
    +#define HCR_API (UL(1) << 41)
    +#define HCR_APK (UL(1) << 40)
    #define HCR_TEA (UL(1) << 37)
    #define HCR_TERR (UL(1) << 36)
    #define HCR_TLOR (UL(1) << 35)
    @@ -87,7 +89,7 @@
    HCR_AMO | HCR_SWIO | HCR_TIDCP | HCR_RW | HCR_TLOR | \
    HCR_FMO | HCR_IMO)
    #define HCR_VIRT_EXCP_MASK (HCR_VSE | HCR_VI | HCR_VF)
    -#define HCR_HOST_NVHE_FLAGS (HCR_RW)
    +#define HCR_HOST_NVHE_FLAGS (HCR_RW | HCR_API | HCR_APK)
    #define HCR_HOST_VHE_FLAGS (HCR_RW | HCR_TGE | HCR_E2H)

    /* TCR_EL2 Registers bits */
    --
    2.11.0
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