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

Avi Kivity
2010-12-07T13:24:22Z

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