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x86/entry: Add fred_entry_from_kvm() for VMX to handle IRQ/NMI

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In IRQ/NMI induced VM exits, KVM VMX needs to execute the respective
handlers, which requires the software to create a FRED stack frame,
and use it to invoke the handlers. Add fred_irq_entry_from_kvm() for
this job.

Export fred_entry_from_kvm() because VMX can be compiled as a module.

Suggested-by: Sean Christopherson <seanjc@google.com>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Xin Li <xin3.li@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Shan Kang <shan.kang@intel.com>
Link: https://lore.kernel.org/r/20231205105030.8698-32-xin3.li@intel.com
This commit is contained in:
Xin Li 2023-12-05 02:50:20 -08:00 committed by Borislav Petkov (AMD)
parent 2333f3c473
commit 2e670358ec
3 changed files with 109 additions and 0 deletions
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77
arch/x86/entry/entry_64_fred.S
View file

@ -3,8 +3,11 @@
* The actual FRED entry points.
*/
#include <linux/export.h>
#include <asm/asm.h>
#include <asm/fred.h>
#include <asm/segment.h>
#include "calling.h"
@ -52,3 +55,77 @@ SYM_CODE_START_NOALIGN(asm_fred_entrypoint_kernel)
FRED_EXIT
ERETS
SYM_CODE_END(asm_fred_entrypoint_kernel)
#if IS_ENABLED(CONFIG_KVM_INTEL)
SYM_FUNC_START(asm_fred_entry_from_kvm)
push %rbp
mov %rsp, %rbp
UNWIND_HINT_SAVE
/*
* Both IRQ and NMI from VMX can be handled on current task stack
* because there is no need to protect from reentrancy and the call
* stack leading to this helper is effectively constant and shallow
* (relatively speaking). Do the same when FRED is active, i.e., no
* need to check current stack level for a stack switch.
*
* Emulate the FRED-defined redzone and stack alignment.
*/
sub $(FRED_CONFIG_REDZONE_AMOUNT << 6), %rsp
and $FRED_STACK_FRAME_RSP_MASK, %rsp
/*
* Start to push a FRED stack frame, which is always 64 bytes:
*
* +--------+-----------------+
* | Bytes | Usage |
* +--------+-----------------+
* | 63:56 | Reserved |
* | 55:48 | Event Data |
* | 47:40 | SS + Event Info |
* | 39:32 | RSP |
* | 31:24 | RFLAGS |
* | 23:16 | CS + Aux Info |
* | 15:8 | RIP |
* | 7:0 | Error Code |
* +--------+-----------------+
*/
push $0 /* Reserved, must be 0 */
push $0 /* Event data, 0 for IRQ/NMI */
push %rdi /* fred_ss handed in by the caller */
push %rbp
pushf
mov $__KERNEL_CS, %rax
push %rax
/*
* Unlike the IDT event delivery, FRED _always_ pushes an error code
* after pushing the return RIP, thus the CALL instruction CANNOT be
* used here to push the return RIP, otherwise there is no chance to
* push an error code before invoking the IRQ/NMI handler.
*
* Use LEA to get the return RIP and push it, then push an error code.
*/
lea 1f(%rip), %rax
push %rax /* Return RIP */
push $0 /* Error code, 0 for IRQ/NMI */
PUSH_AND_CLEAR_REGS clear_bp=0 unwind_hint=0
movq %rsp, %rdi /* %rdi -> pt_regs */
call __fred_entry_from_kvm /* Call the C entry point */
POP_REGS
ERETS
1:
/*
* Objtool doesn't understand what ERETS does, this hint tells it that
* yes, we'll reach here and with what stack state. A save/restore pair
* isn't strictly needed, but it's the simplest form.
*/
UNWIND_HINT_RESTORE
pop %rbp
RET
SYM_FUNC_END(asm_fred_entry_from_kvm)
EXPORT_SYMBOL_GPL(asm_fred_entry_from_kvm);
#endif

14
arch/x86/entry/entry_fred.c
View file

@ -257,3 +257,17 @@ __visible noinstr void fred_entry_from_kernel(struct pt_regs *regs)
return fred_bad_type(regs, error_code);
}
#if IS_ENABLED(CONFIG_KVM_INTEL)
__visible noinstr void __fred_entry_from_kvm(struct pt_regs *regs)
{
switch (regs->fred_ss.type) {
case EVENT_TYPE_EXTINT:
return fred_extint(regs);
case EVENT_TYPE_NMI:
return fred_exc_nmi(regs);
default:
WARN_ON_ONCE(1);
}
}
#endif

18
arch/x86/include/asm/fred.h
View file

@ -9,6 +9,7 @@
#include <linux/const.h>
#include <asm/asm.h>
#include <asm/trapnr.h>
/*
* FRED event return instruction opcodes for ERET{S,U}; supported in
@ -62,12 +63,29 @@ static __always_inline unsigned long fred_event_data(struct pt_regs *regs)
void asm_fred_entrypoint_user(void);
void asm_fred_entrypoint_kernel(void);
void asm_fred_entry_from_kvm(struct fred_ss);
__visible void fred_entry_from_user(struct pt_regs *regs);
__visible void fred_entry_from_kernel(struct pt_regs *regs);
__visible void __fred_entry_from_kvm(struct pt_regs *regs);
/* Can be called from noinstr code, thus __always_inline */
static __always_inline void fred_entry_from_kvm(unsigned int type, unsigned int vector)
{
struct fred_ss ss = {
.ss =__KERNEL_DS,
.type = type,
.vector = vector,
.nmi = type == EVENT_TYPE_NMI,
.lm = 1,
};
asm_fred_entry_from_kvm(ss);
}
#else /* CONFIG_X86_FRED */
static __always_inline unsigned long fred_event_data(struct pt_regs *regs) { return 0; }
static __always_inline void fred_entry_from_kvm(unsigned int type, unsigned int vector) { }
#endif /* CONFIG_X86_FRED */
#endif /* !__ASSEMBLY__ */