| Message ID | 20220629130514.15780-1-pdurrant@amazon.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v5] KVM: x86/xen: Update Xen CPUID Leaf 4 (tsc info) sub-leaves, if present | expand |
On Wed, Jun 29, 2022, Paul Durrant wrote: > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index 88a3026ee163..abb0a39f60eb 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -638,6 +638,7 @@ struct kvm_vcpu_xen { > struct hrtimer timer; > int poll_evtchn; > struct timer_list poll_timer; > + u32 cpuid_tsc_info; I would prefer to follow vcpu->arch.kvm_cpuid_base and capture the base CPUID function. I have a hard time believing this will be the only case where KVM needs to query XEN CPUID leafs. And cpuid_tsc_info is a confusing name given the helper kvm_xen_setup_tsc_info(); it's odd to see a "setup" helper immediately consume a variable with the same name. It'll incur another CPUID lookup in the update path to check the limit, but again that should be a rare operation so it doesn't seem too onerous. > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 031678eff28e..29ed665c51db 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -3110,6 +3110,7 @@ static int kvm_guest_time_update(struct kvm_vcpu *v) > &vcpu->hv_clock.tsc_shift, > &vcpu->hv_clock.tsc_to_system_mul); > vcpu->hw_tsc_khz = tgt_tsc_khz; > + kvm_xen_setup_tsc_info(v); Any objection to s/setup/update? KVM Xen uses "setup" for things like configuring the event channel using userspace input, whereas this is purely updating existing data structures. > } > > vcpu->hv_clock.tsc_timestamp = tsc_timestamp; > diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c > index 610beba35907..c84424d5c8b6 100644 > --- a/arch/x86/kvm/xen.c > +++ b/arch/x86/kvm/xen.c > @@ -10,6 +10,9 @@ > #include "xen.h" > #include "hyperv.h" > #include "lapic.h" > +#include "cpuid.h" > + > +#include <asm/xen/cpuid.h> > > #include <linux/eventfd.h> > #include <linux/kvm_host.h> > @@ -1855,3 +1858,51 @@ void kvm_xen_destroy_vm(struct kvm *kvm) > if (kvm->arch.xen_hvm_config.msr) > static_branch_slow_dec_deferred(&kvm_xen_enabled); > } > + > +void kvm_xen_after_set_cpuid(struct kvm_vcpu *vcpu) > +{ > + u32 base = 0; > + u32 limit; > + u32 function; > + > + vcpu->arch.xen.cpuid_tsc_info = 0; > + > + for_each_possible_hypervisor_cpuid_base(function) { > + struct kvm_cpuid_entry2 *entry = kvm_find_cpuid_entry(vcpu, function, 0); > + > + if (entry && > + entry->ebx == XEN_CPUID_SIGNATURE_EBX && > + entry->ecx == XEN_CPUID_SIGNATURE_ECX && > + entry->edx == XEN_CPUID_SIGNATURE_EDX) { > + base = function; > + limit = entry->eax; > + break; > + } > + } > + if (!base) > + return; Rather than open code a variant of kvm_update_kvm_cpuid_base(), that helper can be tweaked to take a signature. Along with a patch to provide a #define for Xen's signature as a string, this entire function becomes a one-liner. If the below looks ok (won't compile, needs prep patches), I'll test and post a proper mini-series. --- arch/x86/include/asm/kvm_host.h | 1 + arch/x86/kvm/cpuid.c | 2 ++ arch/x86/kvm/x86.c | 1 + arch/x86/kvm/xen.c | 30 ++++++++++++++++++++++++++++++ arch/x86/kvm/xen.h | 22 +++++++++++++++++++++- 5 files changed, 55 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index de5a149d0971..b2565d05fc86 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -638,6 +638,7 @@ struct kvm_vcpu_xen { struct hrtimer timer; int poll_evtchn; struct timer_list poll_timer; + u32 cpuid_base; }; struct kvm_vcpu_arch { diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 0abe3adc9ae3..54ed51799b8d 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -25,6 +25,7 @@ #include "mmu.h" #include "trace.h" #include "pmu.h" +#include "xen.h" /* * Unlike "struct cpuinfo_x86.x86_capability", kvm_cpu_caps doesn't need to be @@ -309,6 +310,7 @@ static void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) __cr4_reserved_bits(guest_cpuid_has, vcpu); kvm_hv_set_cpuid(vcpu); + kvm_xen_after_set_cpuid(vcpu); /* Invoke the vendor callback only after the above state is updated. */ static_call(kvm_x86_vcpu_after_set_cpuid)(vcpu); diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 567d13405445..a624293c66c8 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3110,6 +3110,7 @@ static int kvm_guest_time_update(struct kvm_vcpu *v) &vcpu->hv_clock.tsc_shift, &vcpu->hv_clock.tsc_to_system_mul); vcpu->hw_tsc_khz = tgt_tsc_khz; + kvm_xen_update_tsc_info(v); } vcpu->hv_clock.tsc_timestamp = tsc_timestamp; diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c index 610beba35907..3fc0c194b813 100644 --- a/arch/x86/kvm/xen.c +++ b/arch/x86/kvm/xen.c @@ -10,6 +10,9 @@ #include "xen.h" #include "hyperv.h" #include "lapic.h" +#include "cpuid.h" + +#include <asm/xen/cpuid.h> #include <linux/eventfd.h> #include <linux/kvm_host.h> @@ -1855,3 +1858,30 @@ void kvm_xen_destroy_vm(struct kvm *kvm) if (kvm->arch.xen_hvm_config.msr) static_branch_slow_dec_deferred(&kvm_xen_enabled); } + +void kvm_xen_update_tsc_info(struct kvm_vcpu *vcpu) +{ + struct kvm_cpuid_entry2 *entry; + u32 function; + + if (!vcpu->arch.xen.cpuid_base) + return; + + entry = kvm_find_cpuid_entry(vcpu, vcpu->arch.xen.cpuid_base, 0); + if (WARN_ON_ONCE(!entry)) + return; + + function = vcpu->arch.xen.cpuid_base | XEN_CPUID_LEAF(3); + if (function > entry->eax) + return; + + entry = kvm_find_cpuid_entry(vcpu, function, 1); + if (entry) { + entry->ecx = vcpu->arch.hv_clock.tsc_to_system_mul; + entry->edx = vcpu->arch.hv_clock.tsc_shift; + } + + entry = kvm_find_cpuid_entry(vcpu, function, 2); + if (entry) + entry->eax = vcpu->arch.hw_tsc_khz; +} diff --git a/arch/x86/kvm/xen.h b/arch/x86/kvm/xen.h index 532a535a9e99..b8161b99b82a 100644 --- a/arch/x86/kvm/xen.h +++ b/arch/x86/kvm/xen.h @@ -9,9 +9,14 @@ #ifndef __ARCH_X86_KVM_XEN_H__ #define __ARCH_X86_KVM_XEN_H__ -#ifdef CONFIG_KVM_XEN #include <linux/jump_label_ratelimit.h> +#include <asm/xen/cpuid.h> + +#include "cpuid.h" + +#ifdef CONFIG_KVM_XEN + extern struct static_key_false_deferred kvm_xen_enabled; int __kvm_xen_has_interrupt(struct kvm_vcpu *vcpu); @@ -32,6 +37,13 @@ int kvm_xen_set_evtchn_fast(struct kvm_xen_evtchn *xe, int kvm_xen_setup_evtchn(struct kvm *kvm, struct kvm_kernel_irq_routing_entry *e, const struct kvm_irq_routing_entry *ue); +void kvm_xen_update_tsc_info(struct kvm_vcpu *vcpu); + +static inline void kvm_xen_after_set_cpuid(struct kvm_vcpu *vcpu) +{ + vcpu->arch.xen.cpuid_base = + kvm_get_hypervisor_cpuid_base(vcpu, XEN_CPUID_SIGNATURE); +} static inline bool kvm_xen_msr_enabled(struct kvm *kvm) { @@ -135,6 +147,14 @@ static inline bool kvm_xen_timer_enabled(struct kvm_vcpu *vcpu) { return false; } + +static inline void kvm_xen_after_set_cpuid(struct kvm_vcpu *vcpu) +{ +} + +static inline void kvm_xen_update_tsc_info(struct kvm_vcpu *vcpu) +{ +} #endif int kvm_xen_hypercall(struct kvm_vcpu *vcpu); base-commit: b08b2f54c49d8f96a22107c444d500dff73ec2a6 --
> -----Original Message----- > From: Sean Christopherson <seanjc@google.com> > Sent: 12 July 2022 00:44 > To: Durrant, Paul <pdurrant@amazon.co.uk> > Cc: x86@kernel.org; kvm@vger.kernel.org; linux-kernel@vger.kernel.org; David Woodhouse > <dwmw2@infradead.org>; Paolo Bonzini <pbonzini@redhat.com>; Vitaly Kuznetsov <vkuznets@redhat.com>; > Wanpeng Li <wanpengli@tencent.com>; Jim Mattson <jmattson@google.com>; Joerg Roedel <joro@8bytes.org>; > Thomas Gleixner <tglx@linutronix.de>; Ingo Molnar <mingo@redhat.com>; Borislav Petkov <bp@alien8.de>; > Dave Hansen <dave.hansen@linux.intel.com>; H. Peter Anvin <hpa@zytor.com> > Subject: RE: [EXTERNAL][PATCH v5] KVM: x86/xen: Update Xen CPUID Leaf 4 (tsc info) sub-leaves, if > present > > CAUTION: This email originated from outside of the organization. Do not click links or open > attachments unless you can confirm the sender and know the content is safe. > > > > On Wed, Jun 29, 2022, Paul Durrant wrote: > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > > index 88a3026ee163..abb0a39f60eb 100644 > > --- a/arch/x86/include/asm/kvm_host.h > > +++ b/arch/x86/include/asm/kvm_host.h > > @@ -638,6 +638,7 @@ struct kvm_vcpu_xen { > > struct hrtimer timer; > > int poll_evtchn; > > struct timer_list poll_timer; > > + u32 cpuid_tsc_info; > > I would prefer to follow vcpu->arch.kvm_cpuid_base and capture the base CPUID > function. I have a hard time believing this will be the only case where KVM needs > to query XEN CPUID leafs. And cpuid_tsc_info is a confusing name given the helper > kvm_xen_setup_tsc_info(); it's odd to see a "setup" helper immediately consume a > variable with the same name. Sure. It is rather shrink-to-fit at the moment... no problem with capturing the base. > > It'll incur another CPUID lookup in the update path to check the limit, but again > that should be a rare operation so it doesn't seem too onerous. > We could capture the limit leaf in the general case. It's not Xen-specific after all. > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > > index 031678eff28e..29ed665c51db 100644 > > --- a/arch/x86/kvm/x86.c > > +++ b/arch/x86/kvm/x86.c > > @@ -3110,6 +3110,7 @@ static int kvm_guest_time_update(struct kvm_vcpu *v) > > &vcpu->hv_clock.tsc_shift, > > &vcpu->hv_clock.tsc_to_system_mul); > > vcpu->hw_tsc_khz = tgt_tsc_khz; > > + kvm_xen_setup_tsc_info(v); > > Any objection to s/setup/update? KVM Xen uses "setup" for things like configuring > the event channel using userspace input, whereas this is purely updating existing > data structures. > Sure. > > } > > > > vcpu->hv_clock.tsc_timestamp = tsc_timestamp; > > diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c > > index 610beba35907..c84424d5c8b6 100644 > > --- a/arch/x86/kvm/xen.c > > +++ b/arch/x86/kvm/xen.c > > @@ -10,6 +10,9 @@ > > #include "xen.h" > > #include "hyperv.h" > > #include "lapic.h" > > +#include "cpuid.h" > > + > > +#include <asm/xen/cpuid.h> > > > > #include <linux/eventfd.h> > > #include <linux/kvm_host.h> > > @@ -1855,3 +1858,51 @@ void kvm_xen_destroy_vm(struct kvm *kvm) > > if (kvm->arch.xen_hvm_config.msr) > > static_branch_slow_dec_deferred(&kvm_xen_enabled); > > } > > + > > +void kvm_xen_after_set_cpuid(struct kvm_vcpu *vcpu) > > +{ > > + u32 base = 0; > > + u32 limit; > > + u32 function; > > + > > + vcpu->arch.xen.cpuid_tsc_info = 0; > > + > > + for_each_possible_hypervisor_cpuid_base(function) { > > + struct kvm_cpuid_entry2 *entry = kvm_find_cpuid_entry(vcpu, function, 0); > > + > > + if (entry && > > + entry->ebx == XEN_CPUID_SIGNATURE_EBX && > > + entry->ecx == XEN_CPUID_SIGNATURE_ECX && > > + entry->edx == XEN_CPUID_SIGNATURE_EDX) { > > + base = function; > > + limit = entry->eax; > > + break; > > + } > > + } > > + if (!base) > > + return; > > Rather than open code a variant of kvm_update_kvm_cpuid_base(), that helper can > be tweaked to take a signature. Along with a patch to provide a #define for Xen's > signature as a string, this entire function becomes a one-liner. > Sure, but as said above, we could make capturing the limit part of the general function too. It could even be extended to capture the Hyper-V base/limit too. As for defining the sig as a string... I guess it would be neater to use the values from the Xen header, but it'll probably make the code more ugly so a secondary definition is reasonable. > If the below looks ok (won't compile, needs prep patches), I'll test and post a > proper mini-series. Ok. Thanks, Paul > > --- > arch/x86/include/asm/kvm_host.h | 1 + > arch/x86/kvm/cpuid.c | 2 ++ > arch/x86/kvm/x86.c | 1 + > arch/x86/kvm/xen.c | 30 ++++++++++++++++++++++++++++++ > arch/x86/kvm/xen.h | 22 +++++++++++++++++++++- > 5 files changed, 55 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index de5a149d0971..b2565d05fc86 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -638,6 +638,7 @@ struct kvm_vcpu_xen { > struct hrtimer timer; > int poll_evtchn; > struct timer_list poll_timer; > + u32 cpuid_base; > }; > > struct kvm_vcpu_arch { > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > index 0abe3adc9ae3..54ed51799b8d 100644 > --- a/arch/x86/kvm/cpuid.c > +++ b/arch/x86/kvm/cpuid.c > @@ -25,6 +25,7 @@ > #include "mmu.h" > #include "trace.h" > #include "pmu.h" > +#include "xen.h" > > /* > * Unlike "struct cpuinfo_x86.x86_capability", kvm_cpu_caps doesn't need to be > @@ -309,6 +310,7 @@ static void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) > __cr4_reserved_bits(guest_cpuid_has, vcpu); > > kvm_hv_set_cpuid(vcpu); > + kvm_xen_after_set_cpuid(vcpu); > > /* Invoke the vendor callback only after the above state is updated. */ > static_call(kvm_x86_vcpu_after_set_cpuid)(vcpu); > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 567d13405445..a624293c66c8 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -3110,6 +3110,7 @@ static int kvm_guest_time_update(struct kvm_vcpu *v) > &vcpu->hv_clock.tsc_shift, > &vcpu->hv_clock.tsc_to_system_mul); > vcpu->hw_tsc_khz = tgt_tsc_khz; > + kvm_xen_update_tsc_info(v); > } > > vcpu->hv_clock.tsc_timestamp = tsc_timestamp; > diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c > index 610beba35907..3fc0c194b813 100644 > --- a/arch/x86/kvm/xen.c > +++ b/arch/x86/kvm/xen.c > @@ -10,6 +10,9 @@ > #include "xen.h" > #include "hyperv.h" > #include "lapic.h" > +#include "cpuid.h" > + > +#include <asm/xen/cpuid.h> > > #include <linux/eventfd.h> > #include <linux/kvm_host.h> > @@ -1855,3 +1858,30 @@ void kvm_xen_destroy_vm(struct kvm *kvm) > if (kvm->arch.xen_hvm_config.msr) > static_branch_slow_dec_deferred(&kvm_xen_enabled); > } > + > +void kvm_xen_update_tsc_info(struct kvm_vcpu *vcpu) > +{ > + struct kvm_cpuid_entry2 *entry; > + u32 function; > + > + if (!vcpu->arch.xen.cpuid_base) > + return; > + > + entry = kvm_find_cpuid_entry(vcpu, vcpu->arch.xen.cpuid_base, 0); > + if (WARN_ON_ONCE(!entry)) > + return; > + > + function = vcpu->arch.xen.cpuid_base | XEN_CPUID_LEAF(3); > + if (function > entry->eax) > + return; > + > + entry = kvm_find_cpuid_entry(vcpu, function, 1); > + if (entry) { > + entry->ecx = vcpu->arch.hv_clock.tsc_to_system_mul; > + entry->edx = vcpu->arch.hv_clock.tsc_shift; > + } > + > + entry = kvm_find_cpuid_entry(vcpu, function, 2); > + if (entry) > + entry->eax = vcpu->arch.hw_tsc_khz; > +} > diff --git a/arch/x86/kvm/xen.h b/arch/x86/kvm/xen.h > index 532a535a9e99..b8161b99b82a 100644 > --- a/arch/x86/kvm/xen.h > +++ b/arch/x86/kvm/xen.h > @@ -9,9 +9,14 @@ > #ifndef __ARCH_X86_KVM_XEN_H__ > #define __ARCH_X86_KVM_XEN_H__ > > -#ifdef CONFIG_KVM_XEN > #include <linux/jump_label_ratelimit.h> > > +#include <asm/xen/cpuid.h> > + > +#include "cpuid.h" > + > +#ifdef CONFIG_KVM_XEN > + > extern struct static_key_false_deferred kvm_xen_enabled; > > int __kvm_xen_has_interrupt(struct kvm_vcpu *vcpu); > @@ -32,6 +37,13 @@ int kvm_xen_set_evtchn_fast(struct kvm_xen_evtchn *xe, > int kvm_xen_setup_evtchn(struct kvm *kvm, > struct kvm_kernel_irq_routing_entry *e, > const struct kvm_irq_routing_entry *ue); > +void kvm_xen_update_tsc_info(struct kvm_vcpu *vcpu); > + > +static inline void kvm_xen_after_set_cpuid(struct kvm_vcpu *vcpu) > +{ > + vcpu->arch.xen.cpuid_base = > + kvm_get_hypervisor_cpuid_base(vcpu, XEN_CPUID_SIGNATURE); > +} > > static inline bool kvm_xen_msr_enabled(struct kvm *kvm) > { > @@ -135,6 +147,14 @@ static inline bool kvm_xen_timer_enabled(struct kvm_vcpu *vcpu) > { > return false; > } > + > +static inline void kvm_xen_after_set_cpuid(struct kvm_vcpu *vcpu) > +{ > +} > + > +static inline void kvm_xen_update_tsc_info(struct kvm_vcpu *vcpu) > +{ > +} > #endif > > int kvm_xen_hypercall(struct kvm_vcpu *vcpu); > > base-commit: b08b2f54c49d8f96a22107c444d500dff73ec2a6 > --
On Tue, Jul 12, 2022, Durrant, Paul wrote: > > > @@ -1855,3 +1858,51 @@ void kvm_xen_destroy_vm(struct kvm *kvm) > > > if (kvm->arch.xen_hvm_config.msr) > > > static_branch_slow_dec_deferred(&kvm_xen_enabled); > > > } > > > + > > > +void kvm_xen_after_set_cpuid(struct kvm_vcpu *vcpu) > > > +{ > > > + u32 base = 0; > > > + u32 limit; > > > + u32 function; > > > + > > > + vcpu->arch.xen.cpuid_tsc_info = 0; > > > + > > > + for_each_possible_hypervisor_cpuid_base(function) { > > > + struct kvm_cpuid_entry2 *entry = kvm_find_cpuid_entry(vcpu, function, 0); > > > + > > > + if (entry && > > > + entry->ebx == XEN_CPUID_SIGNATURE_EBX && > > > + entry->ecx == XEN_CPUID_SIGNATURE_ECX && > > > + entry->edx == XEN_CPUID_SIGNATURE_EDX) { > > > + base = function; > > > + limit = entry->eax; > > > + break; > > > + } > > > + } > > > + if (!base) > > > + return; > > > > Rather than open code a variant of kvm_update_kvm_cpuid_base(), that helper can > > be tweaked to take a signature. Along with a patch to provide a #define for Xen's > > signature as a string, this entire function becomes a one-liner. > > > > Sure, but as said above, we could make capturing the limit part of the > general function too. It could even be extended to capture the Hyper-V > base/limit too. As for defining the sig as a string... I guess it would be > neater to use the values from the Xen header, but it'll probably make the > code more ugly so a secondary definition is reasonable. The base needs to be captured separately for KVM and Xen because KVM (and presumably Xen itself since Xen also allows a variable base) supports advertising multiple hypervisors to the guest. I don't know if there are any guests that will concurrently utilize multiple hypervisor's paravirt features, so maybe we could squeak by, but saving 4 bytes isn't worth the risk. AFAIK, Hyper-V doesn't allow for a variable base, and so doesn't utilize the for_each_possible... macro.
Sean Christopherson <seanjc@google.com> writes: > On Tue, Jul 12, 2022, Durrant, Paul wrote: >> > > @@ -1855,3 +1858,51 @@ void kvm_xen_destroy_vm(struct kvm *kvm) >> > > if (kvm->arch.xen_hvm_config.msr) >> > > static_branch_slow_dec_deferred(&kvm_xen_enabled); >> > > } >> > > + >> > > +void kvm_xen_after_set_cpuid(struct kvm_vcpu *vcpu) >> > > +{ >> > > + u32 base = 0; >> > > + u32 limit; >> > > + u32 function; >> > > + >> > > + vcpu->arch.xen.cpuid_tsc_info = 0; >> > > + >> > > + for_each_possible_hypervisor_cpuid_base(function) { >> > > + struct kvm_cpuid_entry2 *entry = kvm_find_cpuid_entry(vcpu, function, 0); >> > > + >> > > + if (entry && >> > > + entry->ebx == XEN_CPUID_SIGNATURE_EBX && >> > > + entry->ecx == XEN_CPUID_SIGNATURE_ECX && >> > > + entry->edx == XEN_CPUID_SIGNATURE_EDX) { >> > > + base = function; >> > > + limit = entry->eax; >> > > + break; >> > > + } >> > > + } >> > > + if (!base) >> > > + return; >> > >> > Rather than open code a variant of kvm_update_kvm_cpuid_base(), that helper can >> > be tweaked to take a signature. Along with a patch to provide a #define for Xen's >> > signature as a string, this entire function becomes a one-liner. >> > >> >> Sure, but as said above, we could make capturing the limit part of the >> general function too. It could even be extended to capture the Hyper-V >> base/limit too. As for defining the sig as a string... I guess it would be >> neater to use the values from the Xen header, but it'll probably make the >> code more ugly so a secondary definition is reasonable. > > The base needs to be captured separately for KVM and Xen because KVM (and presumably > Xen itself since Xen also allows a variable base) supports advertising multiple > hypervisors to the guest. I don't know if there are any guests that will concurrently > utilize multiple hypervisor's paravirt features, so maybe we could squeak by, but > saving 4 bytes isn't worth the risk. > > AFAIK, Hyper-V doesn't allow for a variable base, and so doesn't utilize the > for_each_possible... macro. FWIW, this matches my understanding too: Windows guests don't seem to check anything besides 0x40000001 and give up if Hyper-V's id is not there.
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 88a3026ee163..abb0a39f60eb 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -638,6 +638,7 @@ struct kvm_vcpu_xen { struct hrtimer timer; int poll_evtchn; struct timer_list poll_timer; + u32 cpuid_tsc_info; }; struct kvm_vcpu_arch { diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index d47222ab8e6e..544d0f823ee5 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -25,6 +25,7 @@ #include "mmu.h" #include "trace.h" #include "pmu.h" +#include "xen.h" /* * Unlike "struct cpuinfo_x86.x86_capability", kvm_cpu_caps doesn't need to be @@ -310,6 +311,7 @@ static void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) __cr4_reserved_bits(guest_cpuid_has, vcpu); kvm_hv_set_cpuid(vcpu); + kvm_xen_after_set_cpuid(vcpu); /* Invoke the vendor callback only after the above state is updated. */ static_call(kvm_x86_vcpu_after_set_cpuid)(vcpu); diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 031678eff28e..29ed665c51db 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3110,6 +3110,7 @@ static int kvm_guest_time_update(struct kvm_vcpu *v) &vcpu->hv_clock.tsc_shift, &vcpu->hv_clock.tsc_to_system_mul); vcpu->hw_tsc_khz = tgt_tsc_khz; + kvm_xen_setup_tsc_info(v); } vcpu->hv_clock.tsc_timestamp = tsc_timestamp; diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c index 610beba35907..c84424d5c8b6 100644 --- a/arch/x86/kvm/xen.c +++ b/arch/x86/kvm/xen.c @@ -10,6 +10,9 @@ #include "xen.h" #include "hyperv.h" #include "lapic.h" +#include "cpuid.h" + +#include <asm/xen/cpuid.h> #include <linux/eventfd.h> #include <linux/kvm_host.h> @@ -1855,3 +1858,51 @@ void kvm_xen_destroy_vm(struct kvm *kvm) if (kvm->arch.xen_hvm_config.msr) static_branch_slow_dec_deferred(&kvm_xen_enabled); } + +void kvm_xen_after_set_cpuid(struct kvm_vcpu *vcpu) +{ + u32 base = 0; + u32 limit; + u32 function; + + vcpu->arch.xen.cpuid_tsc_info = 0; + + for_each_possible_hypervisor_cpuid_base(function) { + struct kvm_cpuid_entry2 *entry = kvm_find_cpuid_entry(vcpu, function, 0); + + if (entry && + entry->ebx == XEN_CPUID_SIGNATURE_EBX && + entry->ecx == XEN_CPUID_SIGNATURE_ECX && + entry->edx == XEN_CPUID_SIGNATURE_EDX) { + base = function; + limit = entry->eax; + break; + } + } + if (!base) + return; + + function = base | XEN_CPUID_LEAF(3); + if (function > limit) + return; + + vcpu->arch.xen.cpuid_tsc_info = function; +} + +void kvm_xen_setup_tsc_info(struct kvm_vcpu *vcpu) +{ + struct kvm_cpuid_entry2 *entry; + + if (!vcpu->arch.xen.cpuid_tsc_info) + return; + + entry = kvm_find_cpuid_entry(vcpu, vcpu->arch.xen.cpuid_tsc_info, 1); + if (entry) { + entry->ecx = vcpu->arch.hv_clock.tsc_to_system_mul; + entry->edx = vcpu->arch.hv_clock.tsc_shift; + } + + entry = kvm_find_cpuid_entry(vcpu, vcpu->arch.xen.cpuid_tsc_info, 2); + if (entry) + entry->eax = vcpu->arch.hw_tsc_khz; +} diff --git a/arch/x86/kvm/xen.h b/arch/x86/kvm/xen.h index 532a535a9e99..b2ca434431d6 100644 --- a/arch/x86/kvm/xen.h +++ b/arch/x86/kvm/xen.h @@ -32,6 +32,8 @@ int kvm_xen_set_evtchn_fast(struct kvm_xen_evtchn *xe, int kvm_xen_setup_evtchn(struct kvm *kvm, struct kvm_kernel_irq_routing_entry *e, const struct kvm_irq_routing_entry *ue); +void kvm_xen_after_set_cpuid(struct kvm_vcpu *vcpu); +void kvm_xen_setup_tsc_info(struct kvm_vcpu *vcpu); static inline bool kvm_xen_msr_enabled(struct kvm *kvm) { @@ -135,6 +137,14 @@ static inline bool kvm_xen_timer_enabled(struct kvm_vcpu *vcpu) { return false; } + +static inline void kvm_xen_after_set_cpuid(struct kvm_vcpu *vcpu) +{ +} + +static inline void kvm_xen_setup_tsc_info(struct kvm_vcpu *vcpu) +{ +} #endif int kvm_xen_hypercall(struct kvm_vcpu *vcpu);
The scaling information in subleaf 1 should match the values set by KVM in the 'vcpu_info' sub-structure 'time_info' (a.k.a. pvclock_vcpu_time_info) which is shared with the guest, but is not directly available to the VMM. The offset values are not set since a TSC offset is already applied. The TSC frequency should also be set in sub-leaf 2. Signed-off-by: Paul Durrant <pdurrant@amazon.com> --- Cc: David Woodhouse <dwmw2@infradead.org> v5: - Drop the caching of the CPUID entry pointers and only update the sub-leaves if the CPU frequency has actually changed v4: - Update commit comment v3: - Add leaf limit check in kvm_xen_set_cpuid() v2: - Make sure sub-leaf pointers are NULLed if the time leaf is removed --- arch/x86/include/asm/kvm_host.h | 1 + arch/x86/kvm/cpuid.c | 2 ++ arch/x86/kvm/x86.c | 1 + arch/x86/kvm/xen.c | 51 +++++++++++++++++++++++++++++++++ arch/x86/kvm/xen.h | 10 +++++++ 5 files changed, 65 insertions(+)