On Tue, Feb 11, 2020 at 05:48:35PM +0000, Marc Zyngier wrote:
> From: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
>
> So far we were flushing almost the entire universe whenever a VM would
> load/unload the SCTLR_EL1 and the two versions of that register had
> different MMU enabled settings. This turned out to be so slow that it
> prevented forward progress for a nested VM, because a scheduler timer
> tick interrupt would always be pending when we reached the nested VM.
>
> To avoid this problem, we consider the SCTLR_EL2 when evaluating if
> caches are on or off when entering virtual EL2 (because this is the
> value that we end up shadowing onto the hardware EL1 register).
>
> Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
> Signed-off-by: Jintack Lim <jintack.lim@xxxxxxxxxx>
> Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
> ---
> arch/arm64/include/asm/kvm_mmu.h | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
> index ee47f7637f28..ec4de0613e7c 100644
> --- a/arch/arm64/include/asm/kvm_mmu.h
> +++ b/arch/arm64/include/asm/kvm_mmu.h
> @@ -88,6 +88,7 @@ alternative_cb_end
> #include <asm/cacheflush.h>
> #include <asm/mmu_context.h>
> #include <asm/pgtable.h>
> +#include <asm/kvm_emulate.h>
>
> void kvm_update_va_mask(struct alt_instr *alt,
> __le32 *origptr, __le32 *updptr, int nr_inst);
> @@ -305,7 +306,10 @@ struct kvm;
>
> static inline bool vcpu_has_cache_enabled(struct kvm_vcpu *vcpu)
> {
> - return (vcpu_read_sys_reg(vcpu, SCTLR_EL1) & 0b101) == 0b101;
> + if (vcpu_mode_el2(vcpu))
> + return (__vcpu_sys_reg(vcpu, SCTLR_EL2) & 0b101) == 0b101;
> + else
> + return (vcpu_read_sys_reg(vcpu, SCTLR_EL1) & 0b101) == 0b101;
> }
How about:
static bool vcpu_has_cache_enabled(struct kvm_vcpu *vcpu)
{
unsigned long cm = SCTLR_ELx_C | SCTLR_ELx_M;
unsigned long sctlr;
if (vcpu_mode_el2(vcpu))
sctlr = __vcpu_sys_reg(vcpu, SCTLR_EL2);
else
sctlr = vcpu_read_sys_reg(vcpu, SCTLR_EL1);
return (sctlr & cm) == cm;
}
... to avoid duplication and make it clearer which fields we're
accessing.
Thanks,
Mark.
>
> static inline void __clean_dcache_guest_page(kvm_pfn_t pfn, unsigned long size)
> --
> 2.20.1
>
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