Re: [PATCH v3] target/i386: Added VGIF feature

[Paolo Bonzini <pbonzini@redhat.com>]

On 30/07/21 09:07, Lara Lazier wrote:
> v2->v3: moved guest check into virtual_gif_enabled
> 
> VGIF allows STGI and CLGI to execute in guest mode and control virtual
> interrupts in guest mode.
> When the VGIF feature is enabled then:
>   * executing STGI in the guest sets bit 9 of the VMCB offset 60h.
>   * executing CLGI in the guest clears bit 9 of the VMCB offset 60h.
> 
> Signed-off-by: Lara Lazier <laramglazier@gmail.com>

This part looks good, I queued it for QEMU 6.2.  However, I am wondering 
if STGI/CLGI should also affect the emulation of VIRQ.  I am not very 
familiar with this part of VGIF because KVM does not need it, but it 
makes sense that STGI/CLGI respectively unmask and mask VIRQ just like 
STI/CLI do.  Can you look up in the manual if there's anything like 
this?  We can discuss the implementation tomorrow.

Thanks,

Paolo

> ---
>   target/i386/cpu.c                   |  3 ++-
>   target/i386/svm.h                   |  6 ++++++
>   target/i386/tcg/sysemu/svm_helper.c | 31 +++++++++++++++++++++++++++--
>   3 files changed, 37 insertions(+), 3 deletions(-)
> 
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index edb97ebbbe..71d26cf1bd 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -631,7 +631,8 @@ void x86_cpu_vendor_words2str(char *dst, uint32_t vendor1,
>   #define TCG_EXT3_FEATURES (CPUID_EXT3_LAHF_LM | CPUID_EXT3_SVM | \
>             CPUID_EXT3_CR8LEG | CPUID_EXT3_ABM | CPUID_EXT3_SSE4A)
>   #define TCG_EXT4_FEATURES 0
> -#define TCG_SVM_FEATURES CPUID_SVM_NPT
> +#define TCG_SVM_FEATURES (CPUID_SVM_NPT | CPUID_SVM_VGIF | \
> +          CPUID_SVM_SVME_ADDR_CHK)
>   #define TCG_KVM_FEATURES 0
>   #define TCG_7_0_EBX_FEATURES (CPUID_7_0_EBX_SMEP | CPUID_7_0_EBX_SMAP | \
>             CPUID_7_0_EBX_BMI1 | CPUID_7_0_EBX_BMI2 | CPUID_7_0_EBX_ADX | \
> diff --git a/target/i386/svm.h b/target/i386/svm.h
> index adc058dc76..036597a2ff 100644
> --- a/target/i386/svm.h
> +++ b/target/i386/svm.h
> @@ -9,6 +9,12 @@
>   #define V_IRQ_SHIFT 8
>   #define V_IRQ_MASK (1 << V_IRQ_SHIFT)
>   
> +#define V_GIF_ENABLED_SHIFT 25
> +#define V_GIF_ENABLED_MASK (1 << V_GIF_ENABLED_SHIFT)
> +
> +#define V_GIF_SHIFT 9
> +#define V_GIF_MASK (1 << V_GIF_SHIFT)
> +
>   #define V_INTR_PRIO_SHIFT 16
>   #define V_INTR_PRIO_MASK (0x0f << V_INTR_PRIO_SHIFT)
>   
> diff --git a/target/i386/tcg/sysemu/svm_helper.c b/target/i386/tcg/sysemu/svm_helper.c
> index 90a9de30f8..b6ad425cca 100644
> --- a/target/i386/tcg/sysemu/svm_helper.c
> +++ b/target/i386/tcg/sysemu/svm_helper.c
> @@ -110,6 +110,17 @@ static inline bool is_efer_invalid_state (CPUX86State *env)
>       return false;
>   }
>   
> +static inline bool virtual_gif_enabled(CPUX86State *env, uint32_t *int_ctl)
> +{
> +    if (likely(env->hflags & HF_GUEST_MASK)) {
> +        *int_ctl = x86_ldl_phys(env_cpu(env),
> +                       env->vm_vmcb + offsetof(struct vmcb, control.int_ctl));
> +        return (env->features[FEAT_SVM] & CPUID_SVM_VGIF)
> +                    && (*int_ctl & V_GIF_ENABLED_MASK);
> +    }
> +    return false;
> +}
> +
>   void helper_vmrun(CPUX86State *env, int aflag, int next_eip_addend)
>   {
>       CPUState *cs = env_cpu(env);
> @@ -503,13 +514,29 @@ void helper_vmsave(CPUX86State *env, int aflag)
>   void helper_stgi(CPUX86State *env)
>   {
>       cpu_svm_check_intercept_param(env, SVM_EXIT_STGI, 0, GETPC());
> -    env->hflags2 |= HF2_GIF_MASK;
> +
> +    CPUState *cs = env_cpu(env);
> +    uint32_t int_ctl;
> +    if (virtual_gif_enabled(env, &int_ctl)) {
> +        x86_stl_phys(cs, env->vm_vmcb + offsetof(struct vmcb, control.int_ctl),
> +                        int_ctl | V_GIF_MASK);
> +    } else {
> +        env->hflags2 |= HF2_GIF_MASK;
> +    }
>   }
>   
>   void helper_clgi(CPUX86State *env)
>   {
>       cpu_svm_check_intercept_param(env, SVM_EXIT_CLGI, 0, GETPC());
> -    env->hflags2 &= ~HF2_GIF_MASK;
> +
> +    CPUState *cs = env_cpu(env);
> +    uint32_t int_ctl;
> +    if (virtual_gif_enabled(env, &int_ctl)) {
> +        x86_stl_phys(cs, env->vm_vmcb + offsetof(struct vmcb, control.int_ctl),
> +                        int_ctl & ~V_GIF_MASK);
> +    } else {
> +        env->hflags2 &= ~HF2_GIF_MASK;
> +    }
>   }
>   
>   bool cpu_svm_has_intercept(CPUX86State *env, uint32_t type)
>