Re: [PATCH for-9.1 v5 2/3] target/i386: add guest-phys-bits cpu property

[Xiaoyao Li <xiaoyao.li@intel.com>]

On 3/25/2024 10:14 PM, Paolo Bonzini wrote:
> From: Gerd Hoffmann <kraxel@redhat.com>
> 
> Allows to set guest-phys-bits (cpuid leaf 80000008, eax[23:16])
> via -cpu $model,guest-phys-bits=$nr.
> 
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> Message-ID: <20240318155336.156197-3-kraxel@redhat.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>

> ---
> v4->v5:
> - move here all non-KVM parts
> - add compat property and support for special value "-1" (accelerator
>    defines value)
> 
>   target/i386/cpu.h |  1 +
>   hw/i386/pc.c      |  4 +++-
>   target/i386/cpu.c | 22 ++++++++++++++++++++++
>   3 files changed, 26 insertions(+), 1 deletion(-)
> 
> diff --git a/target/i386/cpu.h b/target/i386/cpu.h
> index 6b057380791..83e47358451 100644
> --- a/target/i386/cpu.h
> +++ b/target/i386/cpu.h
> @@ -2026,6 +2026,7 @@ struct ArchCPU {
>   
>       /* Number of physical address bits supported */
>       uint32_t phys_bits;
> +    uint32_t guest_phys_bits;
>   
>       /* in order to simplify APIC support, we leave this pointer to the
>          user */
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index 461fcaa1b48..9c4b3969cc8 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -78,7 +78,9 @@
>       { "qemu64-" TYPE_X86_CPU, "model-id", "QEMU Virtual CPU version " v, },\
>       { "athlon-" TYPE_X86_CPU, "model-id", "QEMU Virtual CPU version " v, },
>   
> -GlobalProperty pc_compat_9_0[] = {};
> +GlobalProperty pc_compat_9_0[] = {
> +    { TYPE_X86_CPU, "guest-phys-bits", "0" },
> +};
>   const size_t pc_compat_9_0_len = G_N_ELEMENTS(pc_compat_9_0);
>   
>   GlobalProperty pc_compat_8_2[] = {};
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index 33760a2ee16..eef3d08473e 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -6570,6 +6570,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
>           if (env->features[FEAT_8000_0001_EDX] & CPUID_EXT2_LM) {
>               /* 64 bit processor */
>                *eax |= (cpu_x86_virtual_addr_width(env) << 8);
> +             *eax |= (cpu->guest_phys_bits << 16);
>           }
>           *ebx = env->features[FEAT_8000_0008_EBX];
>           if (cs->nr_cores * cs->nr_threads > 1) {
> @@ -7329,6 +7330,14 @@ static void x86_cpu_realizefn(DeviceState *dev, Error **errp)
>           goto out;
>       }
>   
> +    if (cpu->guest_phys_bits == -1) {
> +        /*
> +         * If it was not set by the user, or by the accelerator via
> +         * cpu_exec_realizefn, clear.
> +         */
> +        cpu->guest_phys_bits = 0;
> +    }
> +
>       if (cpu->ucode_rev == 0) {
>           /*
>            * The default is the same as KVM's. Note that this check
> @@ -7379,6 +7388,14 @@ static void x86_cpu_realizefn(DeviceState *dev, Error **errp)
>           if (cpu->phys_bits == 0) {
>               cpu->phys_bits = TCG_PHYS_ADDR_BITS;
>           }
> +        if (cpu->guest_phys_bits &&
> +            (cpu->guest_phys_bits > cpu->phys_bits ||
> +            cpu->guest_phys_bits < 32)) {
> +            error_setg(errp, "guest-phys-bits should be between 32 and %u "
> +                             " (but is %u)",
> +                             cpu->phys_bits, cpu->guest_phys_bits);
> +            return;
> +        }
>       } else {
>           /* For 32 bit systems don't use the user set value, but keep
>            * phys_bits consistent with what we tell the guest.
> @@ -7387,6 +7404,10 @@ static void x86_cpu_realizefn(DeviceState *dev, Error **errp)
>               error_setg(errp, "phys-bits is not user-configurable in 32 bit");
>               return;
>           }
> +        if (cpu->guest_phys_bits != 0) {
> +            error_setg(errp, "guest-phys-bits is not user-configurable in 32 bit");
> +            return;
> +        }
>   
>           if (env->features[FEAT_1_EDX] & (CPUID_PSE36 | CPUID_PAE)) {
>               cpu->phys_bits = 36;
> @@ -7887,6 +7908,7 @@ static Property x86_cpu_properties[] = {
>       DEFINE_PROP_BOOL("x-force-features", X86CPU, force_features, false),
>       DEFINE_PROP_BOOL("kvm", X86CPU, expose_kvm, true),
>       DEFINE_PROP_UINT32("phys-bits", X86CPU, phys_bits, 0),
> +    DEFINE_PROP_UINT32("guest-phys-bits", X86CPU, guest_phys_bits, -1),
>       DEFINE_PROP_BOOL("host-phys-bits", X86CPU, host_phys_bits, false),
>       DEFINE_PROP_UINT8("host-phys-bits-limit", X86CPU, host_phys_bits_limit, 0),
>       DEFINE_PROP_BOOL("fill-mtrr-mask", X86CPU, fill_mtrr_mask, true),