diff options
| author | Sean Christopherson <seanjc@google.com> | 2022-05-26 21:08:12 +0000 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2022-06-10 10:01:30 -0400 |
| commit | a5ba67b42f07952ec45755bbdd66d7c6e49f555c (patch) | |
| tree | 922211d5ab8816c492fa1a941f9842e43a23ff19 /arch | |
| parent | dfe21e6bc05af433308bc1842da28a8fe28faaa4 (diff) | |
| download | linux-a5ba67b42f07952ec45755bbdd66d7c6e49f555c.tar.bz2 | |
KVM: x86: Omit VCPU_REGS_RIP from emulator's _regs array
Omit RIP from the emulator's _regs array, which is used only for GPRs,
i.e. registers that can be referenced via ModRM and/or SIB bytes. The
emulator uses the dedicated _eip field for RIP, and manually reads from
_eip to handle RIP-relative addressing.
To avoid an even bigger, slightly more dangerous change, hardcode the
number of GPRs to 16 for the time being even though 32-bit KVM's emulator
technically should only have 8 GPRs. Add a TODO to address that in a
future commit.
See also the comments above the read_gpr() and write_gpr() declarations,
and obviously the handling in writeback_registers().
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Message-Id: <20220526210817.3428868-4-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kvm/emulate.c | 10 | ||||
| -rw-r--r-- | arch/x86/kvm/kvm_emulate.h | 13 |
2 files changed, 17 insertions, 6 deletions
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index c58366ae4da2..c74c0fd3b860 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -247,8 +247,8 @@ enum x86_transfer_type { static ulong reg_read(struct x86_emulate_ctxt *ctxt, unsigned nr) { - if (WARN_ON_ONCE(nr >= 16)) - nr &= 16 - 1; + if (WARN_ON_ONCE(nr >= NR_EMULATOR_GPRS)) + nr &= NR_EMULATOR_GPRS - 1; if (!(ctxt->regs_valid & (1 << nr))) { ctxt->regs_valid |= 1 << nr; @@ -259,8 +259,8 @@ static ulong reg_read(struct x86_emulate_ctxt *ctxt, unsigned nr) static ulong *reg_write(struct x86_emulate_ctxt *ctxt, unsigned nr) { - if (WARN_ON_ONCE(nr >= 16)) - nr &= 16 - 1; + if (WARN_ON_ONCE(nr >= NR_EMULATOR_GPRS)) + nr &= NR_EMULATOR_GPRS - 1; ctxt->regs_valid |= 1 << nr; ctxt->regs_dirty |= 1 << nr; @@ -278,7 +278,7 @@ static void writeback_registers(struct x86_emulate_ctxt *ctxt) unsigned long dirty = ctxt->regs_dirty; unsigned reg; - for_each_set_bit(reg, &dirty, 16) + for_each_set_bit(reg, &dirty, NR_EMULATOR_GPRS) ctxt->ops->write_gpr(ctxt, reg, ctxt->_regs[reg]); } diff --git a/arch/x86/kvm/kvm_emulate.h b/arch/x86/kvm/kvm_emulate.h index 8dff25d267b7..bc3f8295c8c8 100644 --- a/arch/x86/kvm/kvm_emulate.h +++ b/arch/x86/kvm/kvm_emulate.h @@ -301,6 +301,17 @@ struct fastop; typedef void (*fastop_t)(struct fastop *); +/* + * The emulator's _regs array tracks only the GPRs, i.e. excludes RIP. RIP is + * tracked/accessed via _eip, and except for RIP relative addressing, which + * also uses _eip, RIP cannot be a register operand nor can it be an operand in + * a ModRM or SIB byte. + * + * TODO: this is technically wrong for 32-bit KVM, which only supports 8 GPRs; + * R8-R15 don't exist. + */ +#define NR_EMULATOR_GPRS 16 + struct x86_emulate_ctxt { void *vcpu; const struct x86_emulate_ops *ops; @@ -363,7 +374,7 @@ struct x86_emulate_ctxt { struct operand src2; struct operand dst; struct operand memop; - unsigned long _regs[NR_VCPU_REGS]; + unsigned long _regs[NR_EMULATOR_GPRS]; struct operand *memopp; struct fetch_cache fetch; struct read_cache io_read; |