Re: [PATCH 2/5] kvm/svm: enhance MOV CR intercept handler

[Avi Kivity <avi@redhat.com>]

On 12/07/2010 12:59 PM, Andre Przywara wrote:
> Newer SVM implementations provide the GPR number in the VMCB, so
> that the emulation path is no longer necesarry to handle CR
> register access intercepts. Implement the handling in svm.c and
> use it when the info is provided.
>
> Signed-off-by: Andre Przywara<andre.przywara@amd.com>
> ---
>   arch/x86/include/asm/svm.h |    2 +
>   arch/x86/kvm/svm.c         |   74 +++++++++++++++++++++++++++++++++++++++-----
>   2 files changed, 68 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h
> index 11dbca7..589fc25 100644
> --- a/arch/x86/include/asm/svm.h
> +++ b/arch/x86/include/asm/svm.h
> @@ -256,6 +256,8 @@ struct __attribute__ ((__packed__)) vmcb {
>   #define SVM_EXITINFOSHIFT_TS_REASON_JMP 38
>   #define SVM_EXITINFOSHIFT_TS_HAS_ERROR_CODE 44
>
> +#define SVM_EXITINFO_REG_MASK 0x0F
> +
>   #define	SVM_EXIT_READ_CR0 	0x000
>   #define	SVM_EXIT_READ_CR3 	0x003
>   #define	SVM_EXIT_READ_CR4 	0x004
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index c573e2d..b7233fd 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -2594,12 +2594,70 @@ static int emulate_on_interception(struct vcpu_svm *svm)
>   	return emulate_instruction(&svm->vcpu, 0, 0, 0) == EMULATE_DONE;
>   }
>
> +static int cr_interception(struct vcpu_svm *svm)
> +{
> +	int reg, cr;
> +	unsigned long val;
> +
> +	if (!boot_cpu_has(SVM_FEATURE_DECODE_ASSIST) ||
> +	    (svm->vmcb->control.exit_info_1&  (1ULL<<  63)) == 0)
> +		return emulate_on_interception(svm);
> +
> +	reg = svm->vmcb->control.exit_info_1&  SVM_EXITINFO_REG_MASK;
> +	cr = svm->vmcb->control.exit_code - SVM_EXIT_READ_CR0;
> +	if (cr>  15) { /* mov to cr */
> +		val = kvm_register_read(&svm->vcpu, reg);
> +		switch (cr&  0x0F) {
> +		case 0:
> +			kvm_set_cr0(&svm->vcpu, val);
> +			break;
> +		case 3:
> +			kvm_set_cr3(&svm->vcpu, val);
> +			break;
> +		case 4:
> +			kvm_set_cr4(&svm->vcpu, val);
> +			break;
> +		case 8:
> +			kvm_set_cr8(&svm->vcpu, val&  0xfUL);
> +			break;
> +		default:
> +			WARN(1, "unhandled write to CR%d", cr&  0x0F);
> +			return EMULATE_FAIL;
> +		}
>

...

> +	}
> +	skip_emulated_instruction(&svm->vcpu);
> +
> +	return 1;
> +}
> +

Must not skip_emulated_instruction() if we inject an exception; see how 
vmx does this (handle_cr).

> @@ -2864,14 +2922,14 @@ static int pause_interception(struct vcpu_svm *svm)
>   }
>
>   static int (*svm_exit_handlers[])(struct vcpu_svm *svm) = {
> -	[SVM_EXIT_READ_CR0]			= emulate_on_interception,
> -	[SVM_EXIT_READ_CR3]			= emulate_on_interception,
> -	[SVM_EXIT_READ_CR4]			= emulate_on_interception,
> -	[SVM_EXIT_READ_CR8]			= emulate_on_interception,
> +	[SVM_EXIT_READ_CR0]			= cr_interception,
> +	[SVM_EXIT_READ_CR3]			= cr_interception,
> +	[SVM_EXIT_READ_CR4]			= cr_interception,
> +	[SVM_EXIT_READ_CR8]			= cr_interception,
>   	[SVM_EXIT_CR0_SEL_WRITE]		= emulate_on_interception,
>   	[SVM_EXIT_WRITE_CR0]			= cr0_write_interception,
> -	[SVM_EXIT_WRITE_CR3]			= emulate_on_interception,
> -	[SVM_EXIT_WRITE_CR4]			= emulate_on_interception,
> +	[SVM_EXIT_WRITE_CR3]			= cr_interception,
> +	[SVM_EXIT_WRITE_CR4]			= cr_interception,
>   	[SVM_EXIT_WRITE_CR8]			= cr8_write_interception,

We could move cr[08]_write_interception into cr_interception, but that 
takes a bit more thought.  Best done later.

>   	[SVM_EXIT_READ_DR0]			= emulate_on_interception,
>   	[SVM_EXIT_READ_DR1]			= emulate_on_interception,


-- 
error compiling committee.c: too many arguments to function