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Message-ID: <5a332064-0a26-4bb9-8a3e-c99604d2d919@redhat.com>
Date: Fri, 16 Feb 2024 07:31:46 +0100
From: Paolo Bonzini <pbonzini@...hat.com>
To: Xin Li <xin@...or.com>, Sean Christopherson <seanjc@...gle.com>,
Max Kellermann <max.kellermann@...os.com>
Cc: hpa@...or.com, x86@...nel.org, linux-kernel@...r.kernel.org,
Stephen Rothwell <sfr@...b.auug.org.au>, kvm@...r.kernel.org
Subject: Re: [PATCH] arch/x86/entry_fred: don't set up KVM IRQs if KVM is
disabled
On 2/16/24 03:10, Xin Li wrote:
> On 2/15/2024 11:55 AM, Sean Christopherson wrote:
>> +Paolo and Stephen
>>
>> FYI, there's a build failure in -next due to a collision between
>> kvm/next and
>> tip/x86/fred. The above makes everything happy.
>>
>> On Thu, Feb 15, 2024, Max Kellermann wrote:
>>> When KVM is disabled, the POSTED_INTR_* macros do not exist, and the
>>> build fails.
>>>
>>> Fixes: 14619d912b65 ("x86/fred: FRED entry/exit and dispatch code")
>>> Signed-off-by: Max Kellermann <max.kellermann@...os.com>
>>> ---
>>> arch/x86/entry/entry_fred.c | 2 ++
>>> 1 file changed, 2 insertions(+)
>>>
>>> diff --git a/arch/x86/entry/entry_fred.c b/arch/x86/entry/entry_fred.c
>>> index ac120cbdaaf2..660b7f7f9a79 100644
>>> --- a/arch/x86/entry/entry_fred.c
>>> +++ b/arch/x86/entry/entry_fred.c
>>> @@ -114,9 +114,11 @@ static idtentry_t
>>> sysvec_table[NR_SYSTEM_VECTORS] __ro_after_init = {
>>> SYSVEC(IRQ_WORK_VECTOR, irq_work),
>>> +#if IS_ENABLED(CONFIG_KVM)
>>> SYSVEC(POSTED_INTR_VECTOR, kvm_posted_intr_ipi),
>>> SYSVEC(POSTED_INTR_WAKEUP_VECTOR, kvm_posted_intr_wakeup_ipi),
>>> SYSVEC(POSTED_INTR_NESTED_VECTOR, kvm_posted_intr_nested_ipi),
>>> +#endif
>>> };
>>> static bool fred_setup_done __initdata;
>>> --
>>> 2.39.2
>
> We want to minimize #ifdeffery (which is why we didn't add any to
> sysvec_table[]), would it be better to simply remove "#if
> IS_ENABLED(CONFIG_KVM)" around the the POSTED_INTR_* macros from the
> Linux-next tree?
>
> BTW, kvm_posted_intr_*() are defined to NULL if !IS_ENABLED(CONFIG_KVM).
It is intentional that KVM-related things are compiled out completely
if !IS_ENABLED(CONFIG_KVM), because then it's also not necessary to have
# define fred_sysvec_kvm_posted_intr_ipi NULL
# define fred_sysvec_kvm_posted_intr_wakeup_ipi NULL
# define fred_sysvec_kvm_posted_intr_nested_ipi NULL
in arch/x86/include/asm/idtentry.h. The full conflict resultion is
diff --git a/arch/x86/entry/entry_fred.c b/arch/x86/entry/entry_fred.c
index ac120cbdaaf2..660b7f7f9a79 100644
--- a/arch/x86/entry/entry_fred.c
+++ b/arch/x86/entry/entry_fred.c
@@ -114,9 +114,11 @@ static idtentry_t sysvec_table[NR_SYSTEM_VECTORS] __ro_after_init = {
SYSVEC(IRQ_WORK_VECTOR, irq_work),
+#if IS_ENABLED(CONFIG_KVM)
SYSVEC(POSTED_INTR_VECTOR, kvm_posted_intr_ipi),
SYSVEC(POSTED_INTR_WAKEUP_VECTOR, kvm_posted_intr_wakeup_ipi),
SYSVEC(POSTED_INTR_NESTED_VECTOR, kvm_posted_intr_nested_ipi),
+#endif
};
static bool fred_setup_done __initdata;
diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index 749c7411d2f1..758f6a2838a8 100644
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -745,10 +745,6 @@ DECLARE_IDTENTRY_SYSVEC(IRQ_WORK_VECTOR, sysvec_irq_work);
DECLARE_IDTENTRY_SYSVEC(POSTED_INTR_VECTOR, sysvec_kvm_posted_intr_ipi);
DECLARE_IDTENTRY_SYSVEC(POSTED_INTR_WAKEUP_VECTOR, sysvec_kvm_posted_intr_wakeup_ipi);
DECLARE_IDTENTRY_SYSVEC(POSTED_INTR_NESTED_VECTOR, sysvec_kvm_posted_intr_nested_ipi);
-#else
-# define fred_sysvec_kvm_posted_intr_ipi NULL
-# define fred_sysvec_kvm_posted_intr_wakeup_ipi NULL
-# define fred_sysvec_kvm_posted_intr_nested_ipi NULL
#endif
#if IS_ENABLED(CONFIG_HYPERV)
and it seems to be a net improvement to me. The #ifs match in
the .h and .c files, and there are no unnecessary initializers
in the sysvec_table.
Paolo
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