| Message ID | ac270005b09c45512504e1e99a80c56f3019496a.1708933498.git.isaku.yamahata@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v19,001/130] x86/virt/tdx: Rename _offset to _member for TD_SYSINFO_MAP() macro | expand |
On 2/26/2024 4:26 PM, isaku.yamahata@intel.com wrote: > From: Chao Gao <chao.gao@intel.com> > > Several MSRs are constant and only used in userspace(ring 3). But VMs may > have different values. KVM uses kvm_set_user_return_msr() to switch to > guest's values and leverages user return notifier to restore them when the > kernel is to return to userspace. To eliminate unnecessary wrmsr, KVM also > caches the value it wrote to an MSR last time. > > TDX module unconditionally resets some of these MSRs to architectural INIT > state on TD exit. It makes the cached values in kvm_user_return_msrs are ^ extra "are" > inconsistent with values in hardware. This inconsistency needs to be > fixed. Otherwise, it may mislead kvm_on_user_return() to skip restoring > some MSRs to the host's values. kvm_set_user_return_msr() can help correct > this case, but it is not optimal as it always does a wrmsr. So, introduce > a variation of kvm_set_user_return_msr() to update cached values and skip > that wrmsr. > > Signed-off-by: Chao Gao <chao.gao@intel.com> > Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com> > Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> > --- > arch/x86/include/asm/kvm_host.h | 1 + > arch/x86/kvm/x86.c | 25 ++++++++++++++++++++----- > 2 files changed, 21 insertions(+), 5 deletions(-) > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index 36694e784c27..3ab85c3d86ee 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -2259,6 +2259,7 @@ int kvm_pv_send_ipi(struct kvm *kvm, unsigned long ipi_bitmap_low, > int kvm_add_user_return_msr(u32 msr); > int kvm_find_user_return_msr(u32 msr); > int kvm_set_user_return_msr(unsigned index, u64 val, u64 mask); > +void kvm_user_return_update_cache(unsigned int index, u64 val); > > static inline bool kvm_is_supported_user_return_msr(u32 msr) > { > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index b361d948140f..1b189e86a1f1 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -440,6 +440,15 @@ static void kvm_user_return_msr_cpu_online(void) > } > } > > +static void kvm_user_return_register_notifier(struct kvm_user_return_msrs *msrs) > +{ > + if (!msrs->registered) { > + msrs->urn.on_user_return = kvm_on_user_return; > + user_return_notifier_register(&msrs->urn); > + msrs->registered = true; > + } > +} > + > int kvm_set_user_return_msr(unsigned slot, u64 value, u64 mask) > { > unsigned int cpu = smp_processor_id(); > @@ -454,15 +463,21 @@ int kvm_set_user_return_msr(unsigned slot, u64 value, u64 mask) > return 1; > > msrs->values[slot].curr = value; > - if (!msrs->registered) { > - msrs->urn.on_user_return = kvm_on_user_return; > - user_return_notifier_register(&msrs->urn); > - msrs->registered = true; > - } > + kvm_user_return_register_notifier(msrs); > return 0; > } > EXPORT_SYMBOL_GPL(kvm_set_user_return_msr); > > +/* Update the cache, "curr", and register the notifier */ Not sure this comment is necessary, since the code is simple. > +void kvm_user_return_update_cache(unsigned int slot, u64 value) As a public API, is it better to use "kvm_user_return_msr_update_cache" instead of "kvm_user_return_update_cache"? Although it makes the API name longer... > +{ > + struct kvm_user_return_msrs *msrs = this_cpu_ptr(user_return_msrs); > + > + msrs->values[slot].curr = value; > + kvm_user_return_register_notifier(msrs); > +} > +EXPORT_SYMBOL_GPL(kvm_user_return_update_cache); > + > static void drop_user_return_notifiers(void) > { > unsigned int cpu = smp_processor_id();
On Sun, Apr 07, 2024 at 01:36:46PM +0800, Binbin Wu <binbin.wu@linux.intel.com> wrote: > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > > index b361d948140f..1b189e86a1f1 100644 > > --- a/arch/x86/kvm/x86.c > > +++ b/arch/x86/kvm/x86.c > > @@ -440,6 +440,15 @@ static void kvm_user_return_msr_cpu_online(void) > > } > > } > > +static void kvm_user_return_register_notifier(struct kvm_user_return_msrs *msrs) > > +{ > > + if (!msrs->registered) { > > + msrs->urn.on_user_return = kvm_on_user_return; > > + user_return_notifier_register(&msrs->urn); > > + msrs->registered = true; > > + } > > +} > > + > > int kvm_set_user_return_msr(unsigned slot, u64 value, u64 mask) > > { > > unsigned int cpu = smp_processor_id(); > > @@ -454,15 +463,21 @@ int kvm_set_user_return_msr(unsigned slot, u64 value, u64 mask) > > return 1; > > msrs->values[slot].curr = value; > > - if (!msrs->registered) { > > - msrs->urn.on_user_return = kvm_on_user_return; > > - user_return_notifier_register(&msrs->urn); > > - msrs->registered = true; > > - } > > + kvm_user_return_register_notifier(msrs); > > return 0; > > } > > EXPORT_SYMBOL_GPL(kvm_set_user_return_msr); > > +/* Update the cache, "curr", and register the notifier */ > Not sure this comment is necessary, since the code is simple. Ok, let's remove it. > > +void kvm_user_return_update_cache(unsigned int slot, u64 value) > > As a public API, is it better to use "kvm_user_return_msr_update_cache" > instead of "kvm_user_return_update_cache"? > Although it makes the API name longer... Yes, other functions consistently user user_return_msr. We should do so.
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 36694e784c27..3ab85c3d86ee 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -2259,6 +2259,7 @@ int kvm_pv_send_ipi(struct kvm *kvm, unsigned long ipi_bitmap_low, int kvm_add_user_return_msr(u32 msr); int kvm_find_user_return_msr(u32 msr); int kvm_set_user_return_msr(unsigned index, u64 val, u64 mask); +void kvm_user_return_update_cache(unsigned int index, u64 val); static inline bool kvm_is_supported_user_return_msr(u32 msr) { diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index b361d948140f..1b189e86a1f1 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -440,6 +440,15 @@ static void kvm_user_return_msr_cpu_online(void) } } +static void kvm_user_return_register_notifier(struct kvm_user_return_msrs *msrs) +{ + if (!msrs->registered) { + msrs->urn.on_user_return = kvm_on_user_return; + user_return_notifier_register(&msrs->urn); + msrs->registered = true; + } +} + int kvm_set_user_return_msr(unsigned slot, u64 value, u64 mask) { unsigned int cpu = smp_processor_id(); @@ -454,15 +463,21 @@ int kvm_set_user_return_msr(unsigned slot, u64 value, u64 mask) return 1; msrs->values[slot].curr = value; - if (!msrs->registered) { - msrs->urn.on_user_return = kvm_on_user_return; - user_return_notifier_register(&msrs->urn); - msrs->registered = true; - } + kvm_user_return_register_notifier(msrs); return 0; } EXPORT_SYMBOL_GPL(kvm_set_user_return_msr); +/* Update the cache, "curr", and register the notifier */ +void kvm_user_return_update_cache(unsigned int slot, u64 value) +{ + struct kvm_user_return_msrs *msrs = this_cpu_ptr(user_return_msrs); + + msrs->values[slot].curr = value; + kvm_user_return_register_notifier(msrs); +} +EXPORT_SYMBOL_GPL(kvm_user_return_update_cache); + static void drop_user_return_notifiers(void) { unsigned int cpu = smp_processor_id();