| Message ID | cca5341a95ac73f904e6300f10b04f9c62e4e8ff.1664550870.git.thomas.lendacky@amd.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Qemu SEV reduced-phys-bits fixes | expand |
* Tom Lendacky (thomas.lendacky@amd.com) wrote: > The value of the reduced-phys-bits parameter is propogated to the CPUID > information exposed to the guest. Update the current validation check to > account for the size of the CPUID field (6-bits), ensuring the value is > in the range of 1 to 63. > > Maintain backward compatibility, to an extent, by allowing a value greater > than 1 (so that the previously documented value of 5 still works), but not > allowing anything over 63. > > Fixes: d8575c6c02 ("sev/i386: add command to initialize the memory encryption context") > Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com> > --- > target/i386/sev.c | 17 ++++++++++++++--- > 1 file changed, 14 insertions(+), 3 deletions(-) > > diff --git a/target/i386/sev.c b/target/i386/sev.c > index 32f7dbac4e..78c2d37eba 100644 > --- a/target/i386/sev.c > +++ b/target/i386/sev.c > @@ -932,15 +932,26 @@ int sev_kvm_init(ConfidentialGuestSupport *cgs, Error **errp) > host_cpuid(0x8000001F, 0, NULL, &ebx, NULL, NULL); > host_cbitpos = ebx & 0x3f; > > + /* > + * The cbitpos value will be placed in bit positions 5:0 of the EBX > + * register of CPUID 0x8000001F. No need to verify the range as the > + * comparison against the host value accomplishes that. > + */ > if (host_cbitpos != sev->cbitpos) { > error_setg(errp, "%s: cbitpos check failed, host '%d' requested '%d'", > __func__, host_cbitpos, sev->cbitpos); > goto err; > } > > - if (sev->reduced_phys_bits < 1) { > - error_setg(errp, "%s: reduced_phys_bits check failed, it should be >=1," > - " requested '%d'", __func__, sev->reduced_phys_bits); > + /* > + * The reduced-phys-bits value will be placed in bit positions 11:6 of > + * the EBX register of CPUID 0x8000001F, so verify the supplied value > + * is in the range of 1 to 63. > + */ > + if (sev->reduced_phys_bits < 1 || sev->reduced_phys_bits > 63) { > + error_setg(errp, "%s: reduced_phys_bits check failed," > + " it should be in the range of 1 to 63, requested '%d'", > + __func__, sev->reduced_phys_bits); > goto err; > } > > -- > 2.37.3 > >
diff --git a/target/i386/sev.c b/target/i386/sev.c index 32f7dbac4e..78c2d37eba 100644 --- a/target/i386/sev.c +++ b/target/i386/sev.c @@ -932,15 +932,26 @@ int sev_kvm_init(ConfidentialGuestSupport *cgs, Error **errp) host_cpuid(0x8000001F, 0, NULL, &ebx, NULL, NULL); host_cbitpos = ebx & 0x3f; + /* + * The cbitpos value will be placed in bit positions 5:0 of the EBX + * register of CPUID 0x8000001F. No need to verify the range as the + * comparison against the host value accomplishes that. + */ if (host_cbitpos != sev->cbitpos) { error_setg(errp, "%s: cbitpos check failed, host '%d' requested '%d'", __func__, host_cbitpos, sev->cbitpos); goto err; } - if (sev->reduced_phys_bits < 1) { - error_setg(errp, "%s: reduced_phys_bits check failed, it should be >=1," - " requested '%d'", __func__, sev->reduced_phys_bits); + /* + * The reduced-phys-bits value will be placed in bit positions 11:6 of + * the EBX register of CPUID 0x8000001F, so verify the supplied value + * is in the range of 1 to 63. + */ + if (sev->reduced_phys_bits < 1 || sev->reduced_phys_bits > 63) { + error_setg(errp, "%s: reduced_phys_bits check failed," + " it should be in the range of 1 to 63, requested '%d'", + __func__, sev->reduced_phys_bits); goto err; }
The value of the reduced-phys-bits parameter is propogated to the CPUID information exposed to the guest. Update the current validation check to account for the size of the CPUID field (6-bits), ensuring the value is in the range of 1 to 63. Maintain backward compatibility, to an extent, by allowing a value greater than 1 (so that the previously documented value of 5 still works), but not allowing anything over 63. Fixes: d8575c6c02 ("sev/i386: add command to initialize the memory encryption context") Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com> --- target/i386/sev.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-)