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| author | Yosry Ahmed <yosry@kernel.org> | 2026-07-13 18:10:17 +0000 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2026-07-22 13:41:54 -0700 |
| commit | e62392bf39ebfdf60d1d082799397fe1cbf8dfc5 (patch) | |
| tree | 7ad41e4ea8ee3570a3b3b04f2981cc2f88ca3206 | |
| parent | 6ccc19d4c1eb97a994180af8afcab58422cb409d (diff) | |
| download | linux-e62392bf39ebfdf60d1d082799397fe1cbf8dfc5.tar.gz linux-e62392bf39ebfdf60d1d082799397fe1cbf8dfc5.zip | |
KVM: x86: Disallow EFER.LME and EFER.LMA if long mode is not supported
Remove EFER.LME and EFER.LMA from EFER reserved bits only if long mode
is actually supported. KVM does check long-mode support before allowing
the bits for guest writes and userspace writes through KVM_SET_SREGS*
(in __kvm_valid_efer()), but userspace writes through KVM_SET_MSRS only
check reserved bits.
In practice, this doesn't really matter. The true motiviation is getting
rid of the #ifdeffery when initializing efer_reserved_bits.
Cc: stable@vger.kernel.org
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260713181020.2735367-3-yosry@kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
| -rw-r--r-- | arch/x86/kvm/msrs.c | 10 | ||||
| -rw-r--r-- | arch/x86/kvm/x86.c | 3 |
2 files changed, 4 insertions, 9 deletions
diff --git a/arch/x86/kvm/msrs.c b/arch/x86/kvm/msrs.c index c230b18d87e3..67481429ad6b 100644 --- a/arch/x86/kvm/msrs.c +++ b/arch/x86/kvm/msrs.c @@ -19,16 +19,8 @@ bool __read_mostly report_ignored_msrs = true; module_param(report_ignored_msrs, bool, 0644); EXPORT_SYMBOL_FOR_KVM_INTERNAL(report_ignored_msrs); -/* EFER defaults: - * - enable syscall per default because its emulated by KVM - * - enable LME and LMA per default on 64 bit KVM - */ -#ifdef CONFIG_X86_64 -static -u64 __read_mostly efer_reserved_bits = ~((u64)(EFER_SCE | EFER_LME | EFER_LMA)); -#else +/* Enable syscall by default because its emulated by KVM */ static u64 __read_mostly efer_reserved_bits = ~((u64)EFER_SCE); -#endif #define MAX_IO_MSRS 256 diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index a4216b858194..0845551c6cab 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -6910,6 +6910,9 @@ EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_setup_xss_caps); static void kvm_setup_efer_caps(void) { + if (kvm_cpu_cap_has(X86_FEATURE_LM)) + kvm_enable_efer_bits(EFER_LME | EFER_LMA); + if (kvm_cpu_cap_has(X86_FEATURE_NX)) kvm_enable_efer_bits(EFER_NX); |