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

Marcelo Tosatti
2010-12-20T12:00:05Z

On Fri, Dec 10, 2010 at 02:51:25PM +0100, 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 | 91 ++++++++++++++++++++++++++++++++++++++-----
> 2 files changed, 82 insertions(+), 11 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 298ff79..ee5f100 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -2594,12 +2594,81 @@ 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;
> + int err;
> +
> + if (!static_cpu_has(X86_FEATURE_DECODEASSISTS))
> + return emulate_on_interception(svm);
> +
> + /* bit 63 is the valid bit, as not all instructions (like lmsw)
> + provide the information */
> + if (unlikely((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;
> +
> + err = 0;
> + if (cr >= 16) { /* mov to cr */
> + cr -= 16;
> + val = kvm_register_read(&svm->vcpu, reg);
> + switch (cr) {
> + case 0:
> + err = kvm_set_cr0(&svm->vcpu, val);
> + break;
> + case 3:
> + err = kvm_set_cr3(&svm->vcpu, val);
> + break;
> + case 4:
> + err = kvm_set_cr4(&svm->vcpu, val);
> + break;
> + case 8:
> + err = kvm_set_cr8(&svm->vcpu, val);
> + break;
> + default:
> + WARN(1, "unhandled write to CR%d", cr);
> + return EMULATE_FAIL;
> + }

Wrong return value? Is WARN() really wanted?