On Mon, Jun 04, 2018 at 04:22:05PM -0400, Konrad Rzeszutek Wilk wrote: > On Mon, Jun 04, 2018 at 05:07:01PM -0300, Eduardo Habkost wrote: > > On Fri, Jun 01, 2018 at 11:38:08AM -0400, Konrad Rzeszutek Wilk wrote: > > > AMD future CPUs expose _two_ ways to utilize the Intel equivalant > > > of the Speculative Store Bypass Disable. The first is via > > > the virtualized VIRT_SPEC CTRL MSR (0xC001_011f) and the second > > > is via the SPEC_CTRL MSR (0x48). The document titled: > > > 124441_AMD64_SpeculativeStoreBypassDisable_Whitepaper_final.pdf > > > > > > gives priority of SPEC CTRL MSR over the VIRT SPEC CTRL MSR. > > > > > > A copy of this document is available at > > > https://bugzilla.kernel.org/show_bug.cgi?id=199889 > > > > > > Anyhow, this means that on future AMD CPUs there will be _two_ ways to > > > deal with SSBD. > > > > Does anybody know if there are AMD CPUs where virt-ssbd won't > > work and would require amd-ssbd to mitigate vulnerabilities? > > > > Also, do we have kernel arch/x86/kvm/cpuid.c patches, already? > > Not yet. They are being discussed right now. I figured I would send > these patches out as a 'Hey, coming at you!', but failed to change > the title to be 'RFC'. OK. I was queueing them on x86-next, but I'm going drop them by now. > > > I prefer to add new CPUID flag names only after the flag name is > > already agreed upon on the kernel side. > > Of course. I will respin once that discussion has calmed down. Thanks! BTW, it looks like the patch on LKML[1] will make bit 26 appear on /proc/cpuinfo as "amd_ssb_no", is that correct? If that's the case, I'd prefer to make the QEMU flag to match the name used by Linux, and be called "amd-ssb-no" (which sounds weird to me, but at least it will be consistent with /proc/cpuinfo). [1] https://patchwork.kernel.org/patch/10443689/ -- Eduardo
