diff options
| author | Sean Christopherson <seanjc@google.com> | 2022-05-26 21:08:13 +0000 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2022-06-10 10:01:30 -0400 |
| commit | 0cbc60d44c35b1070eb4070b499164d27d050576 (patch) | |
| tree | ce1cfd691810beb5465fded0c0a621e6737b138b | |
| parent | a5ba67b42f07952ec45755bbdd66d7c6e49f555c (diff) | |
KVM: x86: Use 16-bit fields to track dirty/valid emulator GPRs
Use a u16 instead of a u32 to track the dirty/valid status of GPRs in the
emulator. Unlike struct kvm_vcpu_arch, x86_emulate_ctxt tracks only the
"true" GPRs, i.e. doesn't include RIP in its array, and so only needs to
track 16 registers.
Note, maxing out at 16 GPRs is a fundamental property of x86-64 and will
not change barring a massive architecture update. Legacy x86 ModRM and
SIB encodings use 3 bits for GPRs, i.e. support 8 registers. x86-64 uses
a single bit in the REX prefix for each possible reference type to double
the number of supported GPRs to 16 registers (4 bits).
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220526210817.3428868-5-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
| -rw-r--r-- | arch/x86/kvm/emulate.c | 3 | ||||
| -rw-r--r-- | arch/x86/kvm/kvm_emulate.h | 4 |
2 files changed, 5 insertions, 2 deletions
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index c74c0fd3b860..5aaf1d1200af 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -262,6 +262,9 @@ static ulong *reg_write(struct x86_emulate_ctxt *ctxt, unsigned nr) if (WARN_ON_ONCE(nr >= NR_EMULATOR_GPRS)) nr &= NR_EMULATOR_GPRS - 1; + BUILD_BUG_ON(sizeof(ctxt->regs_dirty) * BITS_PER_BYTE < NR_EMULATOR_GPRS); + BUILD_BUG_ON(sizeof(ctxt->regs_valid) * BITS_PER_BYTE < NR_EMULATOR_GPRS); + ctxt->regs_valid |= 1 << nr; ctxt->regs_dirty |= 1 << nr; return &ctxt->_regs[nr]; diff --git a/arch/x86/kvm/kvm_emulate.h b/arch/x86/kvm/kvm_emulate.h index bc3f8295c8c8..3a65d6ea7fe6 100644 --- a/arch/x86/kvm/kvm_emulate.h +++ b/arch/x86/kvm/kvm_emulate.h @@ -356,9 +356,9 @@ struct x86_emulate_ctxt { u8 lock_prefix; u8 rep_prefix; /* bitmaps of registers in _regs[] that can be read */ - u32 regs_valid; + u16 regs_valid; /* bitmaps of registers in _regs[] that have been written */ - u32 regs_dirty; + u16 regs_dirty; /* modrm */ u8 modrm; u8 modrm_mod; |