Subject: [PATCH v2 03/10] arm64: KVM: trap VM system registers until MMU and caches are ON

From: [email-masked] (Christoffer Dall)
Date: Wed, 29 Jan 2014 12:07:00 -0800

On Wed, Jan 22, 2014 at 02:56:35PM +0000, Marc Zyngier wrote:
> In order to be able to detect the point where the guest enables
> its MMU and caches, trap all the VM related system registers.
> 
> Once we see the guest enabling both the MMU and the caches, we
> can go back to a saner mode of operation, which is to leave these
> registers in complete control of the guest.
> 
> Signed-off-by: Marc Zyngier <[email-masked]>
> Reviewed-by: Catalin Marinas <[email-masked]>
> ---
>  arch/arm64/include/asm/kvm_arm.h |  3 +-
>  arch/arm64/include/asm/kvm_asm.h |  3 +-
>  arch/arm64/kvm/sys_regs.c        | 99 +++++++++++++++++++++++++++++++++++-----
>  3 files changed, 91 insertions(+), 14 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
> index c98ef47..fd0a651 100644
> --- a/arch/arm64/include/asm/kvm_arm.h
> +++ b/arch/arm64/include/asm/kvm_arm.h
> @@ -62,6 +62,7 @@
>   * RW:		64bit by default, can be overriden for 32bit VMs
>   * TAC:		Trap ACTLR
>   * TSC:		Trap SMC
> + * TVM:		Trap VM ops (until M+C set in SCTLR_EL1)
>   * TSW:		Trap cache operations by set/way
>   * TWE:		Trap WFE
>   * TWI:		Trap WFI
> @@ -74,7 +75,7 @@
>   * SWIO:	Turn set/way invalidates into set/way clean+invalidate
>   */
>  #define HCR_GUEST_FLAGS (HCR_TSC | HCR_TSW | HCR_TWE | HCR_TWI | HCR_VM | \
> -			 HCR_BSU_IS | HCR_FB | HCR_TAC | \
> +			 HCR_TVM | HCR_BSU_IS | HCR_FB | HCR_TAC | \
>  			 HCR_AMO | HCR_IMO | HCR_FMO | \
>  			 HCR_SWIO | HCR_TIDCP | HCR_RW)
>  #define HCR_VIRT_EXCP_MASK (HCR_VA | HCR_VI | HCR_VF)
> diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
> index 3d796b4..89d7796 100644
> --- a/arch/arm64/include/asm/kvm_asm.h
> +++ b/arch/arm64/include/asm/kvm_asm.h
> @@ -81,7 +81,8 @@
>  #define c13_TID_URW	(TPIDR_EL0 * 2)	/* Thread ID, User R/W */
>  #define c13_TID_URO	(TPIDRRO_EL0 * 2)/* Thread ID, User R/O */
>  #define c13_TID_PRIV	(TPIDR_EL1 * 2)	/* Thread ID, Privileged */
> -#define c10_AMAIR	(AMAIR_EL1 * 2)	/* Aux Memory Attr Indirection Reg */
> +#define c10_AMAIR0	(AMAIR_EL1 * 2)	/* Aux Memory Attr Indirection Reg */
> +#define c10_AMAIR1	(c10_AMAIR0 + 1)/* Aux Memory Attr Indirection Reg */
>  #define c14_CNTKCTL	(CNTKCTL_EL1 * 2) /* Timer Control Register (PL1) */
>  #define NR_CP15_REGS	(NR_SYS_REGS * 2)
>  
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index f063750..1a4731b 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -121,6 +121,55 @@ done:
>  }
>  
>  /*
> + * Generic accessor for VM registers. Only called as long as HCR_TVM
> + * is set.
> + */
> +static bool access_vm_reg(struct kvm_vcpu *vcpu,
> +			  const struct sys_reg_params *p,
> +			  const struct sys_reg_desc *r)
> +{
> +	unsigned long val;
> +
> +	BUG_ON(!p->is_write);
> +
> +	val = *vcpu_reg(vcpu, p->Rt);
> +	if (!p->is_aarch32) {
> +		vcpu_sys_reg(vcpu, r->reg) = val;
> +	} else {
> +		vcpu_cp15(vcpu, r->reg) = val & 0xffffffffUL;
> +		if (!p->is_32bit)
> +			vcpu_cp15(vcpu, r->reg + 1) = val >> 32;
> +	}
> +	return true;
> +}
> +
> +/*
> + * SCTLR_EL1 accessor. Only called as long as HCR_TVM is set.  If the
> + * guest enables the MMU, we stop trapping the VM sys_regs and leave
> + * it in complete control of the caches.
> + */
> +static bool access_sctlr(struct kvm_vcpu *vcpu,
> +			 const struct sys_reg_params *p,
> +			 const struct sys_reg_desc *r)
> +{
> +	unsigned long val;
> +
> +	BUG_ON(!p->is_write);
> +
> +	val = *vcpu_reg(vcpu, p->Rt);
> +
> +	if (!p->is_aarch32)
> +		vcpu_sys_reg(vcpu, r->reg) = val;
> +	else
> +		vcpu_cp15(vcpu, r->reg) = val & 0xffffffffUL;

call access_vm_reg()?

> +
> +	if ((val & (0b101)) == 0b101)	/* MMU+Caches enabled? */
> +		vcpu->arch.hcr_el2 &= ~HCR_TVM;

static inline and reuse in patch 1?

static inline bool sctlr_caches_enabled(unsigned long val)
{
	return (val & 0b101) == 0b101;
}

> +
> +	return true;
> +}
> +
> +/*
>   * We could trap ID_DFR0 and tell the guest we don't support performance
>   * monitoring.  Unfortunately the patch to make the kernel check ID_DFR0 was
>   * NAKed, so it will read the PMCR anyway.
> @@ -185,32 +234,32 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>  	  NULL, reset_mpidr, MPIDR_EL1 },
>  	/* SCTLR_EL1 */
>  	{ Op0(0b11), Op1(0b000), CRn(0b0001), CRm(0b0000), Op2(0b000),
> -	  NULL, reset_val, SCTLR_EL1, 0x00C50078 },
> +	  access_sctlr, reset_val, SCTLR_EL1, 0x00C50078 },
>  	/* CPACR_EL1 */
>  	{ Op0(0b11), Op1(0b000), CRn(0b0001), CRm(0b0000), Op2(0b010),
>  	  NULL, reset_val, CPACR_EL1, 0 },
>  	/* TTBR0_EL1 */
>  	{ Op0(0b11), Op1(0b000), CRn(0b0010), CRm(0b0000), Op2(0b000),
> -	  NULL, reset_unknown, TTBR0_EL1 },
> +	  access_vm_reg, reset_unknown, TTBR0_EL1 },
>  	/* TTBR1_EL1 */
>  	{ Op0(0b11), Op1(0b000), CRn(0b0010), CRm(0b0000), Op2(0b001),
> -	  NULL, reset_unknown, TTBR1_EL1 },
> +	  access_vm_reg, reset_unknown, TTBR1_EL1 },
>  	/* TCR_EL1 */
>  	{ Op0(0b11), Op1(0b000), CRn(0b0010), CRm(0b0000), Op2(0b010),
> -	  NULL, reset_val, TCR_EL1, 0 },
> +	  access_vm_reg, reset_val, TCR_EL1, 0 },
>  
>  	/* AFSR0_EL1 */
>  	{ Op0(0b11), Op1(0b000), CRn(0b0101), CRm(0b0001), Op2(0b000),
> -	  NULL, reset_unknown, AFSR0_EL1 },
> +	  access_vm_reg, reset_unknown, AFSR0_EL1 },
>  	/* AFSR1_EL1 */
>  	{ Op0(0b11), Op1(0b000), CRn(0b0101), CRm(0b0001), Op2(0b001),
> -	  NULL, reset_unknown, AFSR1_EL1 },
> +	  access_vm_reg, reset_unknown, AFSR1_EL1 },
>  	/* ESR_EL1 */
>  	{ Op0(0b11), Op1(0b000), CRn(0b0101), CRm(0b0010), Op2(0b000),
> -	  NULL, reset_unknown, ESR_EL1 },
> +	  access_vm_reg, reset_unknown, ESR_EL1 },
>  	/* FAR_EL1 */
>  	{ Op0(0b11), Op1(0b000), CRn(0b0110), CRm(0b0000), Op2(0b000),
> -	  NULL, reset_unknown, FAR_EL1 },
> +	  access_vm_reg, reset_unknown, FAR_EL1 },
>  	/* PAR_EL1 */
>  	{ Op0(0b11), Op1(0b000), CRn(0b0111), CRm(0b0100), Op2(0b000),
>  	  NULL, reset_unknown, PAR_EL1 },
> @@ -224,17 +273,17 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>  
>  	/* MAIR_EL1 */
>  	{ Op0(0b11), Op1(0b000), CRn(0b1010), CRm(0b0010), Op2(0b000),
> -	  NULL, reset_unknown, MAIR_EL1 },
> +	  access_vm_reg, reset_unknown, MAIR_EL1 },
>  	/* AMAIR_EL1 */
>  	{ Op0(0b11), Op1(0b000), CRn(0b1010), CRm(0b0011), Op2(0b000),
> -	  NULL, reset_amair_el1, AMAIR_EL1 },
> +	  access_vm_reg, reset_amair_el1, AMAIR_EL1 },
>  
>  	/* VBAR_EL1 */
>  	{ Op0(0b11), Op1(0b000), CRn(0b1100), CRm(0b0000), Op2(0b000),
>  	  NULL, reset_val, VBAR_EL1, 0 },
>  	/* CONTEXTIDR_EL1 */
>  	{ Op0(0b11), Op1(0b000), CRn(0b1101), CRm(0b0000), Op2(0b001),
> -	  NULL, reset_val, CONTEXTIDR_EL1, 0 },
> +	  access_vm_reg, reset_val, CONTEXTIDR_EL1, 0 },
>  	/* TPIDR_EL1 */
>  	{ Op0(0b11), Op1(0b000), CRn(0b1101), CRm(0b0000), Op2(0b100),
>  	  NULL, reset_unknown, TPIDR_EL1 },
> @@ -305,14 +354,32 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>  	  NULL, reset_val, FPEXC32_EL2, 0x70 },
>  };
>  
> -/* Trapped cp15 registers */
> +/*
> + * Trapped cp15 registers. TTBR0/TTBR1 get a double encoding,
> + * depending on the way they are accessed (as a 32bit or a 64bit
> + * register).
> + */
>  static const struct sys_reg_desc cp15_regs[] = {
> +	{ Op1( 0), CRn( 0), CRm( 2), Op2( 0), access_vm_reg, NULL, c2_TTBR0 },
> +	{ Op1( 0), CRn( 1), CRm( 0), Op2( 0), access_sctlr, NULL, c1_SCTLR },
> +	{ Op1( 0), CRn( 2), CRm( 0), Op2( 0), access_vm_reg, NULL, c2_TTBR0 },
> +	{ Op1( 0), CRn( 2), CRm( 0), Op2( 1), access_vm_reg, NULL, c2_TTBR1 },
> +	{ Op1( 0), CRn( 2), CRm( 0), Op2( 2), access_vm_reg, NULL, c2_TTBCR },
> +	{ Op1( 0), CRn( 3), CRm( 0), Op2( 0), access_vm_reg, NULL, c3_DACR },
> +	{ Op1( 0), CRn( 5), CRm( 0), Op2( 0), access_vm_reg, NULL, c5_DFSR },
> +	{ Op1( 0), CRn( 5), CRm( 0), Op2( 1), access_vm_reg, NULL, c5_IFSR },
> +	{ Op1( 0), CRn( 5), CRm( 1), Op2( 0), access_vm_reg, NULL, c5_ADFSR },
> +	{ Op1( 0), CRn( 5), CRm( 1), Op2( 1), access_vm_reg, NULL, c5_AIFSR },
> +	{ Op1( 0), CRn( 6), CRm( 0), Op2( 0), access_vm_reg, NULL, c6_DFAR },
> +	{ Op1( 0), CRn( 6), CRm( 0), Op2( 2), access_vm_reg, NULL, c6_IFAR },
> +
>  	/*
>  	 * DC{C,I,CI}SW operations:
>  	 */
>  	{ Op1( 0), CRn( 7), CRm( 6), Op2( 2), access_dcsw },
>  	{ Op1( 0), CRn( 7), CRm(10), Op2( 2), access_dcsw },
>  	{ Op1( 0), CRn( 7), CRm(14), Op2( 2), access_dcsw },
> +
>  	{ Op1( 0), CRn( 9), CRm(12), Op2( 0), pm_fake },
>  	{ Op1( 0), CRn( 9), CRm(12), Op2( 1), pm_fake },
>  	{ Op1( 0), CRn( 9), CRm(12), Op2( 2), pm_fake },
> @@ -326,6 +393,14 @@ static const struct sys_reg_desc cp15_regs[] = {
>  	{ Op1( 0), CRn( 9), CRm(14), Op2( 0), pm_fake },
>  	{ Op1( 0), CRn( 9), CRm(14), Op2( 1), pm_fake },
>  	{ Op1( 0), CRn( 9), CRm(14), Op2( 2), pm_fake },
> +
> +	{ Op1( 0), CRn(10), CRm( 2), Op2( 0), access_vm_reg, NULL, c10_PRRR },
> +	{ Op1( 0), CRn(10), CRm( 2), Op2( 1), access_vm_reg, NULL, c10_NMRR },
> +	{ Op1( 0), CRn(10), CRm( 3), Op2( 0), access_vm_reg, NULL, c10_AMAIR0 },
> +	{ Op1( 0), CRn(10), CRm( 3), Op2( 1), access_vm_reg, NULL, c10_AMAIR1 },
> +	{ Op1( 0), CRn(13), CRm( 0), Op2( 1), access_vm_reg, NULL, c13_CID },
> +
> +	{ Op1( 1), CRn( 0), CRm( 2), Op2( 0), access_vm_reg, NULL, c2_TTBR1 },
>  };
>  
>  /* Target specific emulation tables */
> -- 
> 1.8.3.4
> 

Reviewed-by: Christoffer Dall <[email-masked]>