[Xen-devel] Ping: [PATCH] x86: cap address bits CPUID output

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 02.05.16 at 17:11, <JBeulich@xxxxxxxx> wrote:
> Don't use more or report more to guests than we are capable of
> handling.
> 
> At once simplify the code in hvm_cpuid() and mtrr_top_of_ram().
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> --- a/xen/arch/x86/cpu/common.c
> +++ b/xen/arch/x86/cpu/common.c
> @@ -46,6 +46,7 @@ const struct cpu_dev *__read_mostly cpu_
>  
>  unsigned int paddr_bits __read_mostly = 36;
>  unsigned int hap_paddr_bits __read_mostly = 36;
> +unsigned int vaddr_bits __read_mostly = VADDR_BITS;
>  
>  /*
>   * Default host IA32_CR_PAT value to cover all memory types.
> @@ -240,7 +241,14 @@ static void __init early_cpu_detect(void
>       if ( cpuid_eax(0x80000000) >= 0x80000008 ) {
>               eax = cpuid_eax(0x80000008);
>               paddr_bits = eax & 0xff;
> +             if (paddr_bits > PADDR_BITS)
> +                     paddr_bits = PADDR_BITS;
> +             vaddr_bits = (eax >> 8) & 0xff;
> +             if (vaddr_bits > VADDR_BITS)
> +                     vaddr_bits = VADDR_BITS;
>               hap_paddr_bits = ((eax >> 16) & 0xff) ?: paddr_bits;
> +             if (hap_paddr_bits > PADDR_BITS)
> +                     hap_paddr_bits = PADDR_BITS;
>       }
>  }
>  
> --- a/xen/arch/x86/e820.c
> +++ b/xen/arch/x86/e820.c
> @@ -451,11 +451,11 @@ static uint64_t __init mtrr_top_of_ram(v
>           return 0;
>  
>      /* Find the physical address size for this CPU. */
> -    cpuid(0x80000000, &eax, &ebx, &ecx, &edx);
> -    if ( eax >= 0x80000008 )
> +    if ( cpuid_eax(0x80000000) >= 0x80000008 )
>      {
> -        cpuid(0x80000008, &eax, &ebx, &ecx, &edx);
> -        phys_bits = (uint8_t)eax;
> +        phys_bits = (uint8_t)cpuid_eax(0x80000008);
> +        if ( phys_bits > PADDR_BITS )
> +            phys_bits = PADDR_BITS;
>      }
>      addr_mask = ((1ull << phys_bits) - 1) & ~((1ull << 12) - 1);
>  
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -3504,19 +3504,19 @@ void hvm_cpuid(unsigned int input, unsig
>          break;
>  
>      case 0x80000008:
> +        *eax &= 0xff;
>          count = d->arch.paging.gfn_bits + PAGE_SHIFT;
> -        if ( (*eax & 0xff) > count )
> -            *eax = (*eax & ~0xff) | count;
> +        if ( *eax > count )
> +            *eax = count;
>  
>          hvm_cpuid(1, NULL, NULL, NULL, &_edx);
>          count = _edx & (cpufeat_mask(X86_FEATURE_PAE) |
>                          cpufeat_mask(X86_FEATURE_PSE36)) ? 36 : 32;
> -        if ( (*eax & 0xff) < count )
> -            *eax = (*eax & ~0xff) | count;
> +        if ( *eax < count )
> +            *eax = count;
>  
>          hvm_cpuid(0x80000001, NULL, NULL, NULL, &_edx);
> -        *eax = (*eax & ~0xffff00) | (_edx & cpufeat_mask(X86_FEATURE_LM)
> -                                     ? 0x3000 : 0x2000);
> +        *eax |= _edx & cpufeat_mask(X86_FEATURE_LM) ? vaddr_bits << 8 : 
> 0x2000;
>  
>          *ebx &= hvm_featureset[FEATURESET_e8b];
>          break;
> --- a/xen/arch/x86/traps.c
> +++ b/xen/arch/x86/traps.c
> @@ -1146,6 +1146,7 @@ void pv_cpuid(struct cpu_user_regs *regs
>          break;
>  
>      case 0x80000008:
> +        a = paddr_bits | (vaddr_bits << 8);
>          b &= pv_featureset[FEATURESET_e8b];
>          break;
>  
> --- a/xen/include/asm-x86/processor.h
> +++ b/xen/include/asm-x86/processor.h
> @@ -216,10 +216,12 @@ extern bool_t opt_cpu_info;
>  extern u32 cpuid_ext_features;
>  extern u64 trampoline_misc_enable_off;
>  
> -/* Maximum width of physical addresses supported by the hardware */
> +/* Maximum width of physical addresses supported by the hardware. */
>  extern unsigned int paddr_bits;
> -/* Max physical address width supported within HAP guests */
> +/* Max physical address width supported within HAP guests. */
>  extern unsigned int hap_paddr_bits;
> +/* Maximum width of virtual addresses supported by the hardware. */
> +extern unsigned int vaddr_bits;
>  
>  extern const struct x86_cpu_id *x86_match_cpu(const struct x86_cpu_id 
> table[]);
>  




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