On Fri, Jul 08, 2016 at 04:01:39PM +0100, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilb...@redhat.com>
>
> Add the host-phys-bits boolean property, if true, take phys-bits
> from the hosts physical bits value, overriding either the default
> or the user specified value.
>
> We can also use the value we read from the host to check the users
> explicitly set value and warn them if it doesn't match.
>
> Signed-off-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
> ---
[...]
> @@ -2952,28 +2977,57 @@ static void x86_cpu_realizefn(DeviceState *dev, Error
> **errp)
> & CPUID_EXT2_AMD_ALIASES);
> }
>
> + /* For 64bit systems think about the number of physical bits to present.
> + * ideally this should be the same as the host; anything other than
> matching
> + * the host can cause incorrect guest behaviour.
> + * QEMU used to pick the magic value of 40 bits that corresponds to
> + * consumer AMD devices but nothing else.
> + */
> + if (cpu->host_phys_bits && !kvm_enabled()) {
> + error_setg(errp, "phys-bits can not be read from the host in"
> + " TCG mode");
> + return;
> + }
> +
> if (env->features[FEAT_8000_0001_EDX] & CPUID_EXT2_LM) {
> - /* 0 is a special meaning 'use the old default', which matches
> - * the value used by TCG (40).
> - */
> - if (cpu->phys_bits == 0) {
> - cpu->phys_bits = TCG_PHYS_ADDR_BITS;
> - }
> if (kvm_enabled()) {
> - if (cpu->phys_bits > TARGET_PHYS_ADDR_SPACE_BITS ||
> - cpu->phys_bits < 32) {
> + uint32_t host_phys_bits = x86_host_phys_bits();
> + static bool warned;
> +
> + if (cpu->host_phys_bits) {
> + /* The user asked for us to use the host physical bits */
> + cpu->phys_bits = host_phys_bits;
> + }
> +
> + /* Print a warning if the user set it to a value that's not the
> + * host value.
> + */
> + if (cpu->phys_bits != host_phys_bits && cpu->phys_bits != 0 &&
> + !warned) {
> + error_report("Warning: Host physical bits (%u)"
> + " does not match phys-bits property (%u)",
> + host_phys_bits, cpu->phys_bits);
> + warned = true;
> + }
> +
> + if (cpu->phys_bits &&
> + (cpu->phys_bits > TARGET_PHYS_ADDR_SPACE_BITS ||
> + cpu->phys_bits < 32)) {
> error_setg(errp, "phys-bits should be between 32 and %u "
> " (but is %u)",
> TARGET_PHYS_ADDR_SPACE_BITS,
> cpu->phys_bits);
> return;
> }
> } else {
> - if (cpu->phys_bits != TCG_PHYS_ADDR_BITS) {
> + if (cpu->phys_bits && cpu->phys_bits != TCG_PHYS_ADDR_BITS) {
> error_setg(errp, "TCG only supports phys-bits=%u",
> TCG_PHYS_ADDR_BITS);
> return;
> }
> }
> + if (cpu->phys_bits == 0 && !cpu->host_phys_bits) {
Why the !cpu->host_phys_bits check? It seems to be impossible to
have (cpu->host_phys_bits == true && cpu->phys_bits == 0) here.
> + cpu->phys_bits = TCG_PHYS_ADDR_BITS;
> + }
> } else {
> /* For 32 bit systems don't use the user set value, but keep
> * phys_bits consistent with what we tell the guest.
Shouldn't we return error if host-phys-bits is set in 32-bit
mode?
> @@ -3290,6 +3344,7 @@ static Property x86_cpu_properties[] = {
> DEFINE_PROP_BOOL("enforce", X86CPU, enforce_cpuid, false),
> DEFINE_PROP_BOOL("kvm", X86CPU, expose_kvm, true),
> DEFINE_PROP_UINT32("phys-bits", X86CPU, phys_bits, 0),
> + DEFINE_PROP_BOOL("host-phys-bits", X86CPU, host_phys_bits, false),
> DEFINE_PROP_BOOL("fill-mtrr-mask", X86CPU, fill_mtrr_mask, true),
> DEFINE_PROP_UINT32("level", X86CPU, env.cpuid_level, 0),
> DEFINE_PROP_UINT32("xlevel", X86CPU, env.cpuid_xlevel, 0),
> diff --git a/target-i386/cpu.h b/target-i386/cpu.h
> index 9d79146..3c4e64a 100644
> --- a/target-i386/cpu.h
> +++ b/target-i386/cpu.h
> @@ -1184,6 +1184,9 @@ struct X86CPU {
> /* if true fill the top bits of the MTRR_PHYSMASKn variable range */
> bool fill_mtrr_mask;
>
> + /* if true override the phys_bits value with a value read from the host
> */
> + bool host_phys_bits;
> +
> /* Number of physical address bits supported */
> uint32_t phys_bits;
>
> --
> 2.7.4
>
--
Eduardo
