| Message ID | 1548950983-18458-1-git-send-email-yu.c.zhang@linux.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | kvm: x86: Return LA57 feature based on hardware capability | expand |
On 31/01/19 17:09, Yu Zhang wrote: > Previously, 'commit 372fddf70904 ("x86/mm: Introduce the 'no5lvl' kernel > parameter")' cleared X86_FEATURE_LA57 in boot_cpu_data, if Linux chooses > to not run in 5-level paging mode. Yet boot_cpu_data is queried by > do_cpuid_ent() as the host capability later when creating vcpus, and Qemu > will not be able to detect this feature and create VMs with LA57 feature. > > As discussed earlier, VMs can still benefit from extended linear address > width, e.g. to enhance features like ASLR. So we would like to fix this, > by return the true hardware capability when Qemu queries. > > Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com> > --- > Cc: Paolo Bonzini <pbonzini@redhat.com> > Cc: "Radim Krčmář" <rkrcmar@redhat.com> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: Borislav Petkov <bp@alien8.de> > Cc: "H. Peter Anvin" <hpa@zytor.com> > Cc: linux-kernel@vger.kernel.org > --- > arch/x86/kvm/cpuid.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > index bbffa6c..c07958b 100644 > --- a/arch/x86/kvm/cpuid.c > +++ b/arch/x86/kvm/cpuid.c > @@ -335,6 +335,7 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function, > unsigned f_xsaves = kvm_x86_ops->xsaves_supported() ? F(XSAVES) : 0; > unsigned f_umip = kvm_x86_ops->umip_emulated() ? F(UMIP) : 0; > unsigned f_intel_pt = kvm_x86_ops->pt_supported() ? F(INTEL_PT) : 0; > + unsigned f_la57 = 0; > > /* cpuid 1.edx */ > const u32 kvm_cpuid_1_edx_x86_features = > @@ -489,7 +490,10 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function, > // TSC_ADJUST is emulated > entry->ebx |= F(TSC_ADJUST); > entry->ecx &= kvm_cpuid_7_0_ecx_x86_features; > + f_la57 = entry->ecx & F(LA57); > cpuid_mask(&entry->ecx, CPUID_7_ECX); > + /* Set LA57 based on hardware capability. */ > + entry->ecx |= f_la57; > entry->ecx |= f_umip; > /* PKU is not yet implemented for shadow paging. */ > if (!tdp_enabled || !boot_cpu_has(X86_FEATURE_OSPKE)) > Queued for 5.1 past merge window, thanks. Paolo
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index bbffa6c..c07958b 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -335,6 +335,7 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function, unsigned f_xsaves = kvm_x86_ops->xsaves_supported() ? F(XSAVES) : 0; unsigned f_umip = kvm_x86_ops->umip_emulated() ? F(UMIP) : 0; unsigned f_intel_pt = kvm_x86_ops->pt_supported() ? F(INTEL_PT) : 0; + unsigned f_la57 = 0; /* cpuid 1.edx */ const u32 kvm_cpuid_1_edx_x86_features = @@ -489,7 +490,10 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function, // TSC_ADJUST is emulated entry->ebx |= F(TSC_ADJUST); entry->ecx &= kvm_cpuid_7_0_ecx_x86_features; + f_la57 = entry->ecx & F(LA57); cpuid_mask(&entry->ecx, CPUID_7_ECX); + /* Set LA57 based on hardware capability. */ + entry->ecx |= f_la57; entry->ecx |= f_umip; /* PKU is not yet implemented for shadow paging. */ if (!tdp_enabled || !boot_cpu_has(X86_FEATURE_OSPKE))
Previously, 'commit 372fddf70904 ("x86/mm: Introduce the 'no5lvl' kernel parameter")' cleared X86_FEATURE_LA57 in boot_cpu_data, if Linux chooses to not run in 5-level paging mode. Yet boot_cpu_data is queried by do_cpuid_ent() as the host capability later when creating vcpus, and Qemu will not be able to detect this feature and create VMs with LA57 feature. As discussed earlier, VMs can still benefit from extended linear address width, e.g. to enhance features like ASLR. So we would like to fix this, by return the true hardware capability when Qemu queries. Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com> --- Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: "Radim Krčmář" <rkrcmar@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: linux-kernel@vger.kernel.org --- arch/x86/kvm/cpuid.c | 4 ++++ 1 file changed, 4 insertions(+)