On 12/03/2018 17:13, Andy Lutomirski wrote:
>>
>> savesegment(fs, vmx->host_state.fs_sel);
>> /*
>> * When FSGSBASE extensions are enabled, this will have to use
>> * RD{FS,GS}BASE instead of accessing current, and the
>> * corresponding WR{FS,GS}BASE should be done unconditionally,
>> * even if fs_reload_needed (resp. gs_ldt_reload_needed) is 1.
>> */
>> if (vmx->host_state.fs_sel <= 3) {
>> vmcs_write16(HOST_FS_SELECTOR, vmx->host_state.fs_sel);
>> vmcs_write16(HOST_FS_BASE, current->thread.fsbase);
>> vmx->host_state.fs_reload_needed = 0;
>> } else {
>> vmcs_write16(HOST_FS_SELECTOR, 0);
>> vmcs_write16(HOST_FS_BASE, 0);
>> vmx->host_state.fs_reload_needed = 1;
>> }
>> savesegment(gs, vmx->host_state.gs_sel);
>> ...
>>
>> ?
>>
> Hmm, probably, although this still gets the case where the user writes
> 0 to %fs wrong. Of course, save_fsgs() also gets that wrong.
>
> I'm okay with this variant as long as you add a comment to
> save_..._legacy pointing at the KVM code.
Why in save_..._legacy? If it is about FSGSBASE, shouldn't it be in
save_fsgs? (Or if not I'm missing what the comment should be about).
Paolo
