Re: [PATCH v10 33/38] x86/entry: Add fred_entry_from_kvm() for VMX to handle IRQ/NMI

[Paolo Bonzini]

On 9/21/23 14:11, Nikolay Borisov wrote:
> > +SYM_FUNC_START(asm_fred_entry_from_kvm)
> > +    push %rbp
> > +    mov %rsp, %rbp
>
> use FRAME_BEGIN/FRAME_END macros to ommit this code if 
> CONFIG_FRAME_POINTER is disabled.

No, the previous stack pointer is used below, so the code might as well 
use %rbp for that; but it must do so unconditionally.

Paolo

> > +
> > +    UNWIND_HINT_SAVE
> > +
> > +    /*
> > +     * Don't check the FRED stack level, the call stack leading to this
> > +     * helper is effectively constant and shallow (relatively speaking).
> > +     *
> > +     * 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

^^ here

Paolo

> > +    pushf
> > +    mov $__KERNEL_CS, %rax
> > +    push %rax