Re: [PATCH v4 3/3] arm64/kvm: Fine grain _EL2 system registers list that affect nested virtualization

[Marc Zyngier]

On Mon, 16 Oct 2023 12:17:42 +0100,
Miguel Luis <miguel.luis@xxxxxxxxxx> wrote:
> 
> Implement a fine grained approach in the _EL2 sysreg ranges.
> 
> Fixes: d0fc0a2519a6 ("KVM: arm64: nv: Add trap forwarding for HCR_EL2")
> Reviewed-by: Eric Auger <eric.auger@xxxxxxxxxx>
> Signed-off-by: Miguel Luis <miguel.luis@xxxxxxxxxx>
> ---
>  arch/arm64/kvm/emulate-nested.c | 89 ++++++++++++++++++++++++++++++---
>  1 file changed, 83 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm64/kvm/emulate-nested.c b/arch/arm64/kvm/emulate-nested.c
> index 9ced1bf0c2b7..3a7d4003fc2b 100644
> --- a/arch/arm64/kvm/emulate-nested.c
> +++ b/arch/arm64/kvm/emulate-nested.c
> @@ -648,15 +648,92 @@ static const struct encoding_to_trap_config encoding_to_cgt[] __initconst = {
>  	SR_TRAP(SYS_APGAKEYLO_EL1,	CGT_HCR_APK),
>  	SR_TRAP(SYS_APGAKEYHI_EL1,	CGT_HCR_APK),
>  	/* All _EL2 registers */
> -	SR_RANGE_TRAP(sys_reg(3, 4, 0, 0, 0),
> -		      sys_reg(3, 4, 3, 15, 7), CGT_HCR_NV),
> +	SR_TRAP(SYS_BRBCR_EL2,		CGT_HCR_NV),
> +	SR_TRAP(SYS_VPIDR_EL2,		CGT_HCR_NV),
> +	SR_TRAP(SYS_VMPIDR_EL2,		CGT_HCR_NV),
> +	SR_TRAP(SYS_SCTLR_EL2,		CGT_HCR_NV),
> +	SR_TRAP(SYS_ACTLR_EL2,		CGT_HCR_NV),
> +	SR_TRAP(SYS_SCTLR2_EL2,		CGT_HCR_NV),
> +	SR_RANGE_TRAP(SYS_HCR_EL2,
> +		      SYS_HCRX_EL2,	CGT_HCR_NV),
> +	SR_TRAP(SYS_SMPRIMAP_EL2,	CGT_HCR_NV),
> +	SR_TRAP(SYS_SMCR_EL2,		CGT_HCR_NV),
> +	SR_TRAP(SYS_SDER32_EL2,		CGT_HCR_NV),

No. This is a *secure* register. How could it be trapped?

> +	SR_RANGE_TRAP(SYS_TTBR0_EL2,
> +		      SYS_TCR2_EL2,	CGT_HCR_NV),
> +	SR_TRAP(SYS_VTTBR_EL2,		CGT_HCR_NV),
> +	SR_TRAP(SYS_VTCR_EL2,		CGT_HCR_NV),
> +	SR_TRAP(SYS_VNCR_EL2,		CGT_HCR_NV),
> +	SR_TRAP(SYS_VSTTBR_EL2,		CGT_HCR_NV),
> +	SR_TRAP(SYS_VSTCR_EL2,		CGT_HCR_NV),

Secure registers.

> +	SR_TRAP(SYS_DACR32_EL2,		CGT_HCR_NV),

This only exists if EL1 is AArch32 capable. Which contradicts the
basic principle that we don't support AArch32 with NV. Why would you
want to forward such a trap?

> +	SR_RANGE_TRAP(SYS_HDFGRTR_EL2,
> +		      SYS_HAFGRTR_EL2,	CGT_HCR_NV),
>  	/* Skip the SP_EL1 encoding... */
>  	SR_TRAP(SYS_SPSR_EL2,		CGT_HCR_NV),
>  	SR_TRAP(SYS_ELR_EL2,		CGT_HCR_NV),
> -	SR_RANGE_TRAP(sys_reg(3, 4, 4, 1, 1),
> -		      sys_reg(3, 4, 10, 15, 7), CGT_HCR_NV),
> -	SR_RANGE_TRAP(sys_reg(3, 4, 12, 0, 0),
> -		      sys_reg(3, 4, 14, 15, 7), CGT_HCR_NV),
> +	/* SPSR_irq, SPSR_abt, SPSR_und, SPSR_fiq */
> +	SR_RANGE_TRAP(sys_reg(3, 4, 4, 3, 0),
> +		      sys_reg(3, 4, 4, 3, 3), CGT_HCR_NV),
> +	SR_TRAP(SYS_IFSR32_EL2,		CGT_HCR_NV),

Again: AArch32 related register. The spec is very clear that it UNDEFs
when AArch32 doesn't exist. Even the SPSR_* registers should be
removed and handled as RES0 without reinjection of the trap.

> +	SR_TRAP(SYS_AFSR0_EL2,		CGT_HCR_NV),
> +	SR_TRAP(SYS_AFSR1_EL2,		CGT_HCR_NV),
> +	SR_TRAP(SYS_ESR_EL2,		CGT_HCR_NV),
> +	SR_TRAP(SYS_VSESR_EL2,		CGT_HCR_NV),
> +	SR_TRAP(SYS_FPEXC32_EL2,	CGT_HCR_NV),

AArch32.

> +	SR_TRAP(SYS_TFSR_EL2,		CGT_HCR_NV),
> +	SR_TRAP(SYS_FAR_EL2,		CGT_HCR_NV),
> +	SR_TRAP(SYS_HPFAR_EL2,		CGT_HCR_NV),
> +	SR_TRAP(SYS_PMSCR_EL2,		CGT_HCR_NV),
> +	SR_TRAP(SYS_MAIR_EL2,		CGT_HCR_NV),
> +	SR_TRAP(SYS_AMAIR_EL2,		CGT_HCR_NV),
> +	SR_TRAP(SYS_MPAMHCR_EL2,	CGT_HCR_NV),
> +	SR_TRAP(SYS_MPAMVPMV_EL2,	CGT_HCR_NV),
> +	SR_TRAP(SYS_MPAM2_EL2,		CGT_HCR_NV),
> +	SR_RANGE_TRAP(SYS_MPAMVPM0_EL2,
> +		      SYS_MPAMVPM7_EL2,	CGT_HCR_NV),
> +	/*
> +	 * Note that the spec. describes a group of MEC registers
> +	 * whose access should not trap, therefore skip the following:
> +	 * MECID_A0_EL2, MECID_A1_EL2, MECID_P0_EL2,
> +	 * MECID_P1_EL2, MECIDR_EL2, VMECID_A_EL2,
> +	 * VMECID_P_EL2.
> +	 */
> +	SR_RANGE_TRAP(SYS_VBAR_EL2,
> +		      SYS_RMR_EL2,	CGT_HCR_NV),
> +	SR_TRAP(SYS_VDISR_EL2,		CGT_HCR_NV),
> +	/* ICH_AP0R<m>_EL2 */
> +	SR_RANGE_TRAP(SYS_ICH_AP0R0_EL2,
> +		      SYS_ICH_AP0R3_EL2, CGT_HCR_NV),
> +	/* ICH_AP1R<m>_EL2 */
> +	SR_RANGE_TRAP(SYS_ICH_AP1R0_EL2,
> +		      SYS_ICH_AP1R3_EL2, CGT_HCR_NV),
> +	SR_TRAP(SYS_ICC_SRE_EL2,	CGT_HCR_NV),
> +	SR_RANGE_TRAP(SYS_ICH_HCR_EL2,
> +		      SYS_ICH_EISR_EL2,	CGT_HCR_NV),
> +	SR_TRAP(SYS_ICH_ELRSR_EL2,	CGT_HCR_NV),
> +	SR_TRAP(SYS_ICH_VMCR_EL2,	CGT_HCR_NV),
> +	/* ICH_LR<m>_EL2 */
> +	SR_RANGE_TRAP(SYS_ICH_LR0_EL2,
> +		      SYS_ICH_LR15_EL2, CGT_HCR_NV),
> +	SR_TRAP(SYS_CONTEXTIDR_EL2,	CGT_HCR_NV),
> +	SR_TRAP(SYS_TPIDR_EL2,		CGT_HCR_NV),
> +	SR_TRAP(SYS_SCXTNUM_EL2,	CGT_HCR_NV),
> +	/* AMEVCNTVOFF0<n>_EL2, AMEVCNTVOFF1<n>_EL2  */
> +	SR_RANGE_TRAP(SYS_AMEVCNTVOFF0n_EL2(0),
> +		      SYS_AMEVCNTVOFF1n_EL2(15), CGT_HCR_NV),
> +	/* CNT*_EL2 */
> +	SR_TRAP(SYS_CNTVOFF_EL2,	CGT_HCR_NV),
> +	SR_TRAP(SYS_CNTPOFF_EL2,	CGT_HCR_NV),
> +	SR_TRAP(SYS_CNTHCTL_EL2,	CGT_HCR_NV),
> +	SR_RANGE_TRAP(SYS_CNTHP_TVAL_EL2,
> +		      SYS_CNTHP_CVAL_EL2, CGT_HCR_NV),
> +	SR_RANGE_TRAP(SYS_CNTHV_TVAL_EL2,
> +		      SYS_CNTHV_CVAL_EL2, CGT_HCR_NV),
> +	SR_RANGE_TRAP(SYS_CNTHVS_TVAL_EL2,
> +		      SYS_CNTHVS_CVAL_EL2, CGT_HCR_NV),
> +	SR_RANGE_TRAP(SYS_CNTHPS_TVAL_EL2,
> +		      SYS_CNTHPS_CVAL_EL2, CGT_HCR_NV),

None of these secure registers can be accessed, and they will UNDEF at
EL1.

	M.

-- 
Without deviation from the norm, progress is not possible.