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KVM: VMX: Convert launched argument to flags

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Convert __vmx_vcpu_run()'s 'launched' argument to 'flags', in
preparation for doing SPEC_CTRL handling immediately after vmexit, which
will need another flag.

This is much easier than adding a fourth argument, because this code
supports both 32-bit and 64-bit, and the fourth argument on 32-bit would
have to be pushed on the stack.

Note that __vmx_vcpu_run_flags() is called outside of the noinstr
critical section because it will soon start calling potentially
traceable functions.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
This commit is contained in:
Josh Poimboeuf 2022-06-14 23:16:12 +02:00 • committed by Borislav Petkov
parent 8bd200d23e
commit bb06650634
5 changed files with 31 additions and 9 deletions
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2
arch/x86/kvm/vmx/nested.c
View file

@ -3087,7 +3087,7 @@ static int nested_vmx_check_vmentry_hw(struct kvm_vcpu *vcpu)
}
vm_fail = __vmx_vcpu_run(vmx, (unsigned long *)&vcpu->arch.regs,
vmx->loaded_vmcs->launched);
__vmx_vcpu_run_flags(vmx));
if (vmx->msr_autoload.host.nr)
vmcs_write32(VM_EXIT_MSR_LOAD_COUNT, vmx->msr_autoload.host.nr);

7
arch/x86/kvm/vmx/run_flags.h Normal file
View file

@ -0,0 +1,7 @@
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __KVM_X86_VMX_RUN_FLAGS_H
#define __KVM_X86_VMX_RUN_FLAGS_H
#define VMX_RUN_VMRESUME (1 << 0)
#endif /* __KVM_X86_VMX_RUN_FLAGS_H */

9
arch/x86/kvm/vmx/vmenter.S
View file

@ -5,6 +5,7 @@
#include <asm/kvm_vcpu_regs.h>
#include <asm/nospec-branch.h>
#include <asm/segment.h>
#include "run_flags.h"
#define WORD_SIZE (BITS_PER_LONG / 8)
@ -34,7 +35,7 @@
* __vmx_vcpu_run - Run a vCPU via a transition to VMX guest mode
* @vmx: struct vcpu_vmx * (forwarded to vmx_update_host_rsp)
* @regs: unsigned long * (to guest registers)
* @launched: %true if the VMCS has been launched
* @flags: VMX_RUN_VMRESUME: use VMRESUME instead of VMLAUNCH
*
* Returns:
* 0 on VM-Exit, 1 on VM-Fail
@ -59,7 +60,7 @@ SYM_FUNC_START(__vmx_vcpu_run)
*/
push %_ASM_ARG2
/* Copy @launched to BL, _ASM_ARG3 is volatile. */
/* Copy @flags to BL, _ASM_ARG3 is volatile. */
mov %_ASM_ARG3B, %bl
lea (%_ASM_SP), %_ASM_ARG2
@ -69,7 +70,7 @@ SYM_FUNC_START(__vmx_vcpu_run)
mov (%_ASM_SP), %_ASM_AX
/* Check if vmlaunch or vmresume is needed */
testb %bl, %bl
testb $VMX_RUN_VMRESUME, %bl
/* Load guest registers. Don't clobber flags. */
mov VCPU_RCX(%_ASM_AX), %_ASM_CX
@ -92,7 +93,7 @@ SYM_FUNC_START(__vmx_vcpu_run)
mov VCPU_RAX(%_ASM_AX), %_ASM_AX
/* Check EFLAGS.ZF from 'testb' above */
je .Lvmlaunch
jz .Lvmlaunch
/*
* After a successful VMRESUME/VMLAUNCH, control flow "magically"

17
arch/x86/kvm/vmx/vmx.c
View file

@ -839,6 +839,16 @@ static bool msr_write_intercepted(struct vcpu_vmx *vmx, u32 msr)
MSR_IA32_SPEC_CTRL);
}
unsigned int __vmx_vcpu_run_flags(struct vcpu_vmx *vmx)
{
unsigned int flags = 0;
if (vmx->loaded_vmcs->launched)
flags |= VMX_RUN_VMRESUME;
return flags;
}
static void clear_atomic_switch_msr_special(struct vcpu_vmx *vmx,
unsigned long entry, unsigned long exit)
{
@ -6826,7 +6836,8 @@ static fastpath_t vmx_exit_handlers_fastpath(struct kvm_vcpu *vcpu)
}
static noinstr void vmx_vcpu_enter_exit(struct kvm_vcpu *vcpu,
struct vcpu_vmx *vmx)
struct vcpu_vmx *vmx,
unsigned long flags)
{
guest_state_enter_irqoff();
@ -6845,7 +6856,7 @@ static noinstr void vmx_vcpu_enter_exit(struct kvm_vcpu *vcpu,
native_write_cr2(vcpu->arch.cr2);
vmx->fail = __vmx_vcpu_run(vmx, (unsigned long *)&vcpu->arch.regs,
vmx->loaded_vmcs->launched);
flags);
vcpu->arch.cr2 = native_read_cr2();
@ -6953,7 +6964,7 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu)
x86_spec_ctrl_set_guest(vmx->spec_ctrl, 0);
/* The actual VMENTER/EXIT is in the .noinstr.text section. */
vmx_vcpu_enter_exit(vcpu, vmx);
vmx_vcpu_enter_exit(vcpu, vmx, __vmx_vcpu_run_flags(vmx));
/*
* We do not use IBRS in the kernel. If this vCPU has used the

5
arch/x86/kvm/vmx/vmx.h
View file

@ -13,6 +13,7 @@
#include "vmcs.h"
#include "vmx_ops.h"
#include "cpuid.h"
#include "run_flags.h"
#define MSR_TYPE_R 1
#define MSR_TYPE_W 2
@ -404,7 +405,9 @@ void vmx_set_virtual_apic_mode(struct kvm_vcpu *vcpu);
struct vmx_uret_msr *vmx_find_uret_msr(struct vcpu_vmx *vmx, u32 msr);
void pt_update_intercept_for_msr(struct kvm_vcpu *vcpu);
void vmx_update_host_rsp(struct vcpu_vmx *vmx, unsigned long host_rsp);
bool __vmx_vcpu_run(struct vcpu_vmx *vmx, unsigned long *regs, bool launched);
unsigned int __vmx_vcpu_run_flags(struct vcpu_vmx *vmx);
bool __vmx_vcpu_run(struct vcpu_vmx *vmx, unsigned long *regs,
unsigned int flags);
int vmx_find_loadstore_msr_slot(struct vmx_msrs *m, u32 msr);
void vmx_ept_load_pdptrs(struct kvm_vcpu *vcpu);