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| author | Aaron Lewis <aaronlewis@google.com> | 2023-04-04 17:45:15 -0700 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2023-04-11 10:19:03 -0700 |
| commit | 6be3ae45f567cdebb5b9938137bf3445ceacf9fb (patch) | |
| tree | 84ecd4be65938442d421322bd51d8bc7c4be5dc2 /arch/x86/kvm | |
| parent | 7712145073876092e9aa81f0b836fef8b5694b14 (diff) | |
| download | linux-6be3ae45f567cdebb5b9938137bf3445ceacf9fb.tar.gz linux-6be3ae45f567cdebb5b9938137bf3445ceacf9fb.tar.bz2 linux-6be3ae45f567cdebb5b9938137bf3445ceacf9fb.zip | |
KVM: x86: Add a helper to handle filtering of unpermitted XCR0 features
Add a helper, kvm_get_filtered_xcr0(), to dedup code that needs to account
for XCR0 features that require explicit opt-in on a per-process basis. In
addition to documenting when KVM should/shouldn't consult
xstate_get_guest_group_perm(), the helper will also allow sanitizing the
filtered XCR0 to avoid enumerating architecturally illegal XCR0 values,
e.g. XTILE_CFG without XTILE_DATA.
No functional changes intended.
Signed-off-by: Aaron Lewis <aaronlewis@google.com>
Reviewed-by: Mingwei Zhang <mizhang@google.com>
[sean: rename helper, move to x86.h, massage changelog]
Reviewed-by: Aaron Lewis <aaronlewis@google.com>
Tested-by: Aaron Lewis <aaronlewis@google.com>
Link: https://lore.kernel.org/r/20230405004520.421768-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Diffstat (limited to 'arch/x86/kvm')
| -rw-r--r-- | arch/x86/kvm/cpuid.c | 2 | ||||
| -rw-r--r-- | arch/x86/kvm/x86.c | 4 | ||||
| -rw-r--r-- | arch/x86/kvm/x86.h | 13 |
3 files changed, 15 insertions, 4 deletions
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 9583a110cf5f..1daf0df6a9b8 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -1002,7 +1002,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function) entry->eax = entry->ebx = entry->ecx = 0; break; case 0xd: { - u64 permitted_xcr0 = kvm_caps.supported_xcr0 & xstate_get_guest_group_perm(); + u64 permitted_xcr0 = kvm_get_filtered_xcr0(); u64 permitted_xss = kvm_caps.supported_xss; entry->eax &= permitted_xcr0; diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 237c483b1230..181f155933cf 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -4531,9 +4531,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) r = 0; break; case KVM_CAP_XSAVE2: { - u64 guest_perm = xstate_get_guest_group_perm(); - - r = xstate_required_size(kvm_caps.supported_xcr0 & guest_perm, false); + r = xstate_required_size(kvm_get_filtered_xcr0(), false); if (r < sizeof(struct kvm_xsave)) r = sizeof(struct kvm_xsave); break; diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h index a8167b47b8c8..9589c86812eb 100644 --- a/arch/x86/kvm/x86.h +++ b/arch/x86/kvm/x86.h @@ -315,6 +315,19 @@ extern struct kvm_caps kvm_caps; extern bool enable_pmu; +/* + * Get a filtered version of KVM's supported XCR0 that strips out dynamic + * features for which the current process doesn't (yet) have permission to use. + * This is intended to be used only when enumerating support to userspace, + * e.g. in KVM_GET_SUPPORTED_CPUID and KVM_CAP_XSAVE2, it does NOT need to be + * used to check/restrict guest behavior as KVM rejects KVM_SET_CPUID{2} if + * userspace attempts to enable unpermitted features. + */ +static inline u64 kvm_get_filtered_xcr0(void) +{ + return kvm_caps.supported_xcr0 & xstate_get_guest_group_perm(); +} + static inline bool kvm_mpx_supported(void) { return (kvm_caps.supported_xcr0 & (XFEATURE_MASK_BNDREGS | XFEATURE_MASK_BNDCSR)) |