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Message-ID: <9d2cccad-16ee-abcf-5a34-7e513a050229@redhat.com>
Date:   Thu, 21 Sep 2023 14:38:48 +0200
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Subject: Re: [PATCH v10 33/38] x86/entry: Add fred_entry_from_kvm() for VMX to
 handle IRQ/NMI
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To:     Nikolay Borisov <nik.borisov@suse.com>, Xin Li <xin3.li@intel.com>,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-edac@vger.kernel.org, linux-hyperv@vger.kernel.org,
        kvm@vger.kernel.org, xen-devel@lists.xenproject.org
Cc:     tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
        dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com,
        luto@kernel.org, seanjc@google.com, peterz@infradead.org,
        jgross@suse.com, ravi.v.shankar@intel.com, mhiramat@kernel.org,
        andrew.cooper3@citrix.com, jiangshanlai@gmail.com
References: <20230914044805.301390-1-xin3.li@intel.com>
 <20230914044805.301390-34-xin3.li@intel.com>
 <8163cf98-8968-72a4-4193-1ca9f019d9ff@suse.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
In-Reply-To: <8163cf98-8968-72a4-4193-1ca9f019d9ff@suse.com>
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Precedence: bulk

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