Re: [Qemu-devel][PATCH] x86/cpu: Use max host physical address if -cpu max option is applied

[Paolo Bonzini]

On 13/01/21 10:04, Yang Weijiang wrote:
> QEMU option -cpu max(max_features) means "Enables all features supported by
> the accelerator in the current host", this looks true for all the features
> except guest max physical address width, so add this patch to enable it.
>
> Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
> ---
>   target/i386/cpu.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index 35459a38bb..b5943406f7 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -6673,7 +6673,7 @@ static void x86_cpu_realizefn(DeviceState *dev, Error 
> **errp)
>                   warned = true;
>               }
>   
> -            if (cpu->host_phys_bits) {
> +            if (cpu->host_phys_bits || cpu->max_features) {
>                   /* The user asked for us to use the host physical bits */
>                   cpu->phys_bits = host_phys_bits;
>                   if (cpu->host_phys_bits_limit &&

Can you check if this works?

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 35459a38bb..72a79e6019 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -4319,6 +4319,7 @@ static void max_x86_cpu_initfn(Object *obj)
         if (lmce_supported()) {
             object_property_set_bool(OBJECT(cpu), "lmce", true, 
&error_abort);
         }
+        object_property_set_bool(OBJECT(cpu), "host-phys-bits", true, 
&error_abort);
     } else {
         object_property_set_str(OBJECT(cpu), "vendor", CPUID_VENDOR_AMD,
                                 &error_abort);


It should allow people to use -cpu max,host-phys-bits=false.

Thanks,

Paolo