| Message ID | 20200708192546.4068026-1-abhishekbh@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v4] x86/speculation/l1tf: Add KConfig for setting the L1D cache flush mode | expand |
Hi again, On 7/8/20 12:25 PM, Abhishek Bhardwaj wrote: > diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig > index b277a2db62676..1f85374a0b812 100644 > --- a/arch/x86/kvm/Kconfig > +++ b/arch/x86/kvm/Kconfig > @@ -107,4 +107,17 @@ config KVM_MMU_AUDIT > This option adds a R/W kVM module parameter 'mmu_audit', which allows > auditing of KVM MMU events at runtime. > > +config KVM_VMENTRY_L1D_FLUSH > + int "L1D cache flush settings (1-3)" > + range 1 3 > + default "2" > + depends on KVM && X86_64 > + help > + This setting determines the L1D cache flush behavior before a VMENTER. > + This is similar to setting the option / parameter to > + kvm-intel.vmentry_l1d_flush. > + 1 - Never flush. > + 2 - Conditionally flush. > + 3 - Always flush. > + > endif # VIRTUALIZATION If you do a v5, the help text lines (under "help") should be indented with one tab + 2 spaces according to Documentation/process/coding-style.rst.
On Wed, Jul 8, 2020 at 12:34 PM Randy Dunlap <rdunlap@infradead.org> wrote: > > Hi again, > > On 7/8/20 12:25 PM, Abhishek Bhardwaj wrote: > > diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig > > index b277a2db62676..1f85374a0b812 100644 > > --- a/arch/x86/kvm/Kconfig > > +++ b/arch/x86/kvm/Kconfig > > @@ -107,4 +107,17 @@ config KVM_MMU_AUDIT > > This option adds a R/W kVM module parameter 'mmu_audit', which allows > > auditing of KVM MMU events at runtime. > > > > +config KVM_VMENTRY_L1D_FLUSH > > + int "L1D cache flush settings (1-3)" > > + range 1 3 > > + default "2" > > + depends on KVM && X86_64 > > + help > > + This setting determines the L1D cache flush behavior before a VMENTER. > > + This is similar to setting the option / parameter to > > + kvm-intel.vmentry_l1d_flush. > > + 1 - Never flush. > > + 2 - Conditionally flush. > > + 3 - Always flush. > > + > > endif # VIRTUALIZATION > > If you do a v5, the help text lines (under "help") should be indented > with one tab + 2 spaces according to Documentation/process/coding-style.rst. Apologies for missing this. Fixed in v5 - https://lkml.org/lkml/2020/7/8/1369 > > -- > ~Randy >
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 0b71970d2d3d2..1dcc875cf5547 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -1406,7 +1406,15 @@ enum l1tf_mitigations l1tf_mitigation __ro_after_init = L1TF_MITIGATION_FLUSH; #if IS_ENABLED(CONFIG_KVM_INTEL) EXPORT_SYMBOL_GPL(l1tf_mitigation); #endif +#if (CONFIG_KVM_VMENTRY_L1D_FLUSH == 1) +enum vmx_l1d_flush_state l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_NEVER; +#elif (CONFIG_KVM_VMENTRY_L1D_FLUSH == 2) +enum vmx_l1d_flush_state l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_COND; +#elif (CONFIG_KVM_VMENTRY_L1D_FLUSH == 3) +enum vmx_l1d_flush_state l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_ALWAYS; +#else enum vmx_l1d_flush_state l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_AUTO; +#endif EXPORT_SYMBOL_GPL(l1tf_vmx_mitigation); /* diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig index b277a2db62676..1f85374a0b812 100644 --- a/arch/x86/kvm/Kconfig +++ b/arch/x86/kvm/Kconfig @@ -107,4 +107,17 @@ config KVM_MMU_AUDIT This option adds a R/W kVM module parameter 'mmu_audit', which allows auditing of KVM MMU events at runtime. +config KVM_VMENTRY_L1D_FLUSH + int "L1D cache flush settings (1-3)" + range 1 3 + default "2" + depends on KVM && X86_64 + help + This setting determines the L1D cache flush behavior before a VMENTER. + This is similar to setting the option / parameter to + kvm-intel.vmentry_l1d_flush. + 1 - Never flush. + 2 - Conditionally flush. + 3 - Always flush. + endif # VIRTUALIZATION
This change adds a new kernel configuration that sets the l1d cache flush setting at compile time rather than at run time. The reasons for this change are as follows - - Kernel command line arguments are getting unwieldy. These parameters are not a scalable way to set the kernel config. They're intended as a super limited way for the bootloader to pass info to the kernel and also as a way for end users who are not compiling the kernel themselves to tweak the kernel behavior. - Also, if a user wants this setting from the start. It's a definite smell that it deserves to be a compile time thing rather than adding extra code plus whatever miniscule time at runtime to pass an extra argument. - Finally, it doesn't preclude the runtime / kernel command line way. Users are free to use those as well. Signed-off-by: Abhishek Bhardwaj <abhishekbh@google.com> --- Changes in v4: - Add motivation for the change in the commit message. Changes in v3: - Change depends on to only x86_64. - Remove copy paste errors at the end of the KConfig. Changes in v2: - Fix typo in the help of the new KConfig. arch/x86/kernel/cpu/bugs.c | 8 ++++++++ arch/x86/kvm/Kconfig | 13 +++++++++++++ 2 files changed, 21 insertions(+)