On 9/27/21 7:54 AM, Paolo Bonzini wrote: > On 27/09/21 14:28, Borislav Petkov wrote: >> On Mon, Sep 27, 2021 at 02:14:52PM +0200, Paolo Bonzini wrote: >>> Right, not which MSR to write but which value to write. It doesn't know >>> that the PSF disable bit is valid unless the corresponding CPUID bit is >>> set. >> >> There's no need for the separate PSF CPUID bit yet. We have decided for >> now to not control PSF separately but disable it through SSB. Please >> follow this thread: > > There are other guests than Linux. This patch is just telling userspace Yes, That is the reason for this patch. > that KVM knows what the PSFD bit is. It is also possible to expose the > bit in KVM without having any #define in cpufeatures.h or without the > kernel using it. For example KVM had been exposing FSGSBASE long before > Linux supported it. > > That said, the patch is incomplete because it should also add the new > CPUID bit to guest_has_spec_ctrl_msr (what KVM *really* cares about is not > the individual bits, only whether SPEC_CTRL exists at all). Yea, I missed that. Will add it in next revision, Thanks Babu
