On 16/08/17 11:50, Dave Martin wrote: > On Tue, Aug 15, 2017 at 05:33:15PM +0100, Marc Zyngier wrote: >> On 09/08/17 13:05, Dave Martin wrote: >>> Until KVM has full SVE support, guests must not be allowed to >>> execute SVE instructions. >>> >>> This patch enables the necessary traps, and also ensures that the >>> traps are disabled again on exit from the guest so that the host >>> can still use SVE if it wants to. >>> >>> Signed-off-by: Dave Martin <Dave.Martin@xxxxxxx> >>> --- >>> arch/arm64/include/asm/kvm_arm.h | 3 ++- >>> arch/arm64/kvm/hyp/switch.c | 6 +++--- >>> 2 files changed, 5 insertions(+), 4 deletions(-) >>> >>> diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h >>> index dbf0537..8a19651 100644 >>> --- a/arch/arm64/include/asm/kvm_arm.h >>> +++ b/arch/arm64/include/asm/kvm_arm.h >>> @@ -186,7 +186,7 @@ >>> #define CPTR_EL2_TTA (1 << 20) >>> #define CPTR_EL2_TFP (1 << CPTR_EL2_TFP_SHIFT) >>> #define CPTR_EL2_TZ (1 << 8) >>> -#define CPTR_EL2_DEFAULT 0x000033ff >>> +#define CPTR_EL2_DEFAULT (0x000033ff & ~CPTR_EL2_TZ) >> >> I must say I'm not overly fond of this construct. I'd rather introduce a >> RES1 field that matches the v8.2 description, instead of this ugly >> constant and something that clears it. > > Sorry, I don't get your meaning here. v8.2 neither immediately predates > or postdates SVE. The ARMv8 ARM (DDI406B_a, D7.2.19) says otherwise. This bit is only defined as having a possibility of being 0 on an v8.2 implementation if SVE is implemented. > What are you propsing? What I'm proposing is: #define CPTR_EL2_RES1 0x32ff #define CPTR_EL2_DEFAULT CPTR_EL2_RES1 and none of that pointless constant clearing. > I guess we could just write 0x000032ff now that the only meaning the > architecture can ever assign to bit 8 is known. Exactly. M. -- Jazz is not dead. It just smells funny...
