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linux/arch/x86/include/uapi/asm/vmx.h
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Xin Li 885df2d210 KVM: x86: Add support for RDMSR/WRMSRNS w/ immediate on Intel 
Add support for the immediate forms of RDMSR and WRMSRNS (currently
Intel-only).  The immediate variants are only valid in 64-bit mode, and
use a single general purpose register for the data (the register is also
encoded in the instruction, i.e. not implicit like regular RDMSR/WRMSR).

The immediate variants are primarily motivated by performance, not code
size: by having the MSR index in an immediate, it is available *much*
earlier in the CPU pipeline, which allows hardware much more leeway about
how a particular MSR is handled.

Intel VMX support for the immediate forms of MSR accesses communicates
exit information to the host as follows:

  1) The immediate form of RDMSR uses VM-Exit Reason 84.

  2) The immediate form of WRMSRNS uses VM-Exit Reason 85.

  3) For both VM-Exit reasons 84 and 85, the Exit Qualification field is
     set to the MSR index that triggered the VM-Exit.

  4) Bits 3 ~ 6 of the VM-Exit Instruction Information field are set to
     the register encoding used by the immediate form of the instruction,
     i.e. the destination register for RDMSR, and the source for WRMSRNS.

  5) The VM-Exit Instruction Length field records the size of the
     immediate form of the MSR instruction.

To deal with userspace RDMSR exits, stash the destination register in a
new kvm_vcpu_arch field, similar to cui_linear_rip, pio, etc.
Alternatively, the register could be saved in kvm_run.msr or re-retrieved
from the VMCS, but the former would require sanitizing the value to ensure
userspace doesn't clobber the value to an out-of-bounds index, and the
latter would require a new one-off kvm_x86_ops hook.

Don't bother adding support for the instructions in KVM's emulator, as the
only way for RDMSR/WRMSR to be encountered is if KVM is emulating large
swaths of code due to invalid guest state, and a vCPU cannot have invalid
guest state while in 64-bit mode.

Signed-off-by: Xin Li (Intel) <xin@zytor.com>
[sean: minor tweaks, massage and expand changelog]
Link: https://lore.kernel.org/r/20250805202224.1475590-5-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
2025-08-19 11:59:46 -07:00

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/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
/*
* vmx.h: VMX Architecture related definitions
* Copyright (c) 2004, Intel Corporation.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms and conditions of the GNU General Public License,
* version 2, as published by the Free Software Foundation.
*
* This program is distributed in the hope it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*
* You should have received a copy of the GNU General Public License along with
* this program; if not, write to the Free Software Foundation, Inc., 59 Temple
* Place - Suite 330, Boston, MA 02111-1307 USA.
*
* A few random additions are:
* Copyright (C) 2006 Qumranet
* Avi Kivity <avi@qumranet.com>
* Yaniv Kamay <yaniv@qumranet.com>
*
*/
#ifndef _UAPIVMX_H
#define _UAPIVMX_H
#define VMX_EXIT_REASONS_FAILED_VMENTRY 0x80000000
#define VMX_EXIT_REASONS_SGX_ENCLAVE_MODE 0x08000000
#define EXIT_REASON_EXCEPTION_NMI 0
#define EXIT_REASON_EXTERNAL_INTERRUPT 1
#define EXIT_REASON_TRIPLE_FAULT 2
#define EXIT_REASON_INIT_SIGNAL 3
#define EXIT_REASON_SIPI_SIGNAL 4
#define EXIT_REASON_OTHER_SMI 6
#define EXIT_REASON_INTERRUPT_WINDOW 7
#define EXIT_REASON_NMI_WINDOW 8
#define EXIT_REASON_TASK_SWITCH 9
#define EXIT_REASON_CPUID 10
#define EXIT_REASON_HLT 12
#define EXIT_REASON_INVD 13
#define EXIT_REASON_INVLPG 14
#define EXIT_REASON_RDPMC 15
#define EXIT_REASON_RDTSC 16
#define EXIT_REASON_VMCALL 18
#define EXIT_REASON_VMCLEAR 19
#define EXIT_REASON_VMLAUNCH 20
#define EXIT_REASON_VMPTRLD 21
#define EXIT_REASON_VMPTRST 22
#define EXIT_REASON_VMREAD 23
#define EXIT_REASON_VMRESUME 24
#define EXIT_REASON_VMWRITE 25
#define EXIT_REASON_VMOFF 26
#define EXIT_REASON_VMON 27
#define EXIT_REASON_CR_ACCESS 28
#define EXIT_REASON_DR_ACCESS 29
#define EXIT_REASON_IO_INSTRUCTION 30
#define EXIT_REASON_MSR_READ 31
#define EXIT_REASON_MSR_WRITE 32
#define EXIT_REASON_INVALID_STATE 33
#define EXIT_REASON_MSR_LOAD_FAIL 34
#define EXIT_REASON_MWAIT_INSTRUCTION 36
#define EXIT_REASON_MONITOR_TRAP_FLAG 37
#define EXIT_REASON_MONITOR_INSTRUCTION 39
#define EXIT_REASON_PAUSE_INSTRUCTION 40
#define EXIT_REASON_MCE_DURING_VMENTRY 41
#define EXIT_REASON_TPR_BELOW_THRESHOLD 43
#define EXIT_REASON_APIC_ACCESS 44
#define EXIT_REASON_EOI_INDUCED 45
#define EXIT_REASON_GDTR_IDTR 46
#define EXIT_REASON_LDTR_TR 47
#define EXIT_REASON_EPT_VIOLATION 48
#define EXIT_REASON_EPT_MISCONFIG 49
#define EXIT_REASON_INVEPT 50
#define EXIT_REASON_RDTSCP 51
#define EXIT_REASON_PREEMPTION_TIMER 52
#define EXIT_REASON_INVVPID 53
#define EXIT_REASON_WBINVD 54
#define EXIT_REASON_XSETBV 55
#define EXIT_REASON_APIC_WRITE 56
#define EXIT_REASON_RDRAND 57
#define EXIT_REASON_INVPCID 58
#define EXIT_REASON_VMFUNC 59
#define EXIT_REASON_ENCLS 60
#define EXIT_REASON_RDSEED 61
#define EXIT_REASON_PML_FULL 62
#define EXIT_REASON_XSAVES 63
#define EXIT_REASON_XRSTORS 64
#define EXIT_REASON_UMWAIT 67
#define EXIT_REASON_TPAUSE 68
#define EXIT_REASON_BUS_LOCK 74
#define EXIT_REASON_NOTIFY 75
#define EXIT_REASON_TDCALL 77
#define EXIT_REASON_MSR_READ_IMM 84
#define EXIT_REASON_MSR_WRITE_IMM 85
#define VMX_EXIT_REASONS \
{ EXIT_REASON_EXCEPTION_NMI, "EXCEPTION_NMI" }, \
{ EXIT_REASON_EXTERNAL_INTERRUPT, "EXTERNAL_INTERRUPT" }, \
{ EXIT_REASON_TRIPLE_FAULT, "TRIPLE_FAULT" }, \
{ EXIT_REASON_INIT_SIGNAL, "INIT_SIGNAL" }, \
{ EXIT_REASON_SIPI_SIGNAL, "SIPI_SIGNAL" }, \
{ EXIT_REASON_INTERRUPT_WINDOW, "INTERRUPT_WINDOW" }, \
{ EXIT_REASON_NMI_WINDOW, "NMI_WINDOW" }, \
{ EXIT_REASON_TASK_SWITCH, "TASK_SWITCH" }, \
{ EXIT_REASON_CPUID, "CPUID" }, \
{ EXIT_REASON_HLT, "HLT" }, \
{ EXIT_REASON_INVD, "INVD" }, \
{ EXIT_REASON_INVLPG, "INVLPG" }, \
{ EXIT_REASON_RDPMC, "RDPMC" }, \
{ EXIT_REASON_RDTSC, "RDTSC" }, \
{ EXIT_REASON_VMCALL, "VMCALL" }, \
{ EXIT_REASON_VMCLEAR, "VMCLEAR" }, \
{ EXIT_REASON_VMLAUNCH, "VMLAUNCH" }, \
{ EXIT_REASON_VMPTRLD, "VMPTRLD" }, \
{ EXIT_REASON_VMPTRST, "VMPTRST" }, \
{ EXIT_REASON_VMREAD, "VMREAD" }, \
{ EXIT_REASON_VMRESUME, "VMRESUME" }, \
{ EXIT_REASON_VMWRITE, "VMWRITE" }, \
{ EXIT_REASON_VMOFF, "VMOFF" }, \
{ EXIT_REASON_VMON, "VMON" }, \
{ EXIT_REASON_CR_ACCESS, "CR_ACCESS" }, \
{ EXIT_REASON_DR_ACCESS, "DR_ACCESS" }, \
{ EXIT_REASON_IO_INSTRUCTION, "IO_INSTRUCTION" }, \
{ EXIT_REASON_MSR_READ, "MSR_READ" }, \
{ EXIT_REASON_MSR_WRITE, "MSR_WRITE" }, \
{ EXIT_REASON_INVALID_STATE, "INVALID_STATE" }, \
{ EXIT_REASON_MSR_LOAD_FAIL, "MSR_LOAD_FAIL" }, \
{ EXIT_REASON_MWAIT_INSTRUCTION, "MWAIT_INSTRUCTION" }, \
{ EXIT_REASON_MONITOR_TRAP_FLAG, "MONITOR_TRAP_FLAG" }, \
{ EXIT_REASON_MONITOR_INSTRUCTION, "MONITOR_INSTRUCTION" }, \
{ EXIT_REASON_PAUSE_INSTRUCTION, "PAUSE_INSTRUCTION" }, \
{ EXIT_REASON_MCE_DURING_VMENTRY, "MCE_DURING_VMENTRY" }, \
{ EXIT_REASON_TPR_BELOW_THRESHOLD, "TPR_BELOW_THRESHOLD" }, \
{ EXIT_REASON_APIC_ACCESS, "APIC_ACCESS" }, \
{ EXIT_REASON_EOI_INDUCED, "EOI_INDUCED" }, \
{ EXIT_REASON_GDTR_IDTR, "GDTR_IDTR" }, \
{ EXIT_REASON_LDTR_TR, "LDTR_TR" }, \
{ EXIT_REASON_EPT_VIOLATION, "EPT_VIOLATION" }, \
{ EXIT_REASON_EPT_MISCONFIG, "EPT_MISCONFIG" }, \
{ EXIT_REASON_INVEPT, "INVEPT" }, \
{ EXIT_REASON_RDTSCP, "RDTSCP" }, \
{ EXIT_REASON_PREEMPTION_TIMER, "PREEMPTION_TIMER" }, \
{ EXIT_REASON_INVVPID, "INVVPID" }, \
{ EXIT_REASON_WBINVD, "WBINVD" }, \
{ EXIT_REASON_XSETBV, "XSETBV" }, \
{ EXIT_REASON_APIC_WRITE, "APIC_WRITE" }, \
{ EXIT_REASON_RDRAND, "RDRAND" }, \
{ EXIT_REASON_INVPCID, "INVPCID" }, \
{ EXIT_REASON_VMFUNC, "VMFUNC" }, \
{ EXIT_REASON_ENCLS, "ENCLS" }, \
{ EXIT_REASON_RDSEED, "RDSEED" }, \
{ EXIT_REASON_PML_FULL, "PML_FULL" }, \
{ EXIT_REASON_XSAVES, "XSAVES" }, \
{ EXIT_REASON_XRSTORS, "XRSTORS" }, \
{ EXIT_REASON_UMWAIT, "UMWAIT" }, \
{ EXIT_REASON_TPAUSE, "TPAUSE" }, \
{ EXIT_REASON_BUS_LOCK, "BUS_LOCK" }, \
{ EXIT_REASON_NOTIFY, "NOTIFY" }, \
{ EXIT_REASON_TDCALL, "TDCALL" }, \
{ EXIT_REASON_MSR_READ_IMM, "MSR_READ_IMM" }, \
{ EXIT_REASON_MSR_WRITE_IMM, "MSR_WRITE_IMM" }
#define VMX_EXIT_REASON_FLAGS \
{ VMX_EXIT_REASONS_FAILED_VMENTRY, "FAILED_VMENTRY" }
#define VMX_ABORT_SAVE_GUEST_MSR_FAIL 1
#define VMX_ABORT_LOAD_HOST_PDPTE_FAIL 2
#define VMX_ABORT_LOAD_HOST_MSR_FAIL 4
#endif /* _UAPIVMX_H */
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