linux-kernel - Re: [PATCH] kvm: x86: Do not handle MMIO request in fast_page

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Date:   Tue, 5 Sep 2017 18:37:15 +0800
From:   "Du, Changbin" <changbin.du@...el.com>
To:     changbin.du@...el.com
Cc:     pbonzini@...hat.com, rkrcmar@...hat.com, tglx@...utronix.de,
        mingo@...hat.com, hpa@...or.com, x86@...nel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Changbin Du <changbin.du@...mail.com>
Subject: Re: [PATCH] kvm: x86: Do not handle MMIO request in fast_page_fault

Sorry, messed up. This is not the correct one, will resend. thx.

On Tue, Sep 05, 2017 at 05:29:41PM +0800, changbin.du@...el.com wrote:
> From: Changbin Du <changbin.du@...mail.com>
> 
> If it is a MMIO request, it should be handled by slow path. This patch
> actually fixed below warning when mmu debug is enabled.
> 
> WARNING: CPU: 5 PID: 2282 at arch/x86/kvm/mmu.c:226 fast_page_fault+0x41b/0x520
> CPU: 5 PID: 2282 Comm: qemu-system-x86 Not tainted 4.13.0-rc6+ #34
> task: ffff9b47f5286000 task.stack: ffffb18d03b28000
> RIP: 0010:fast_page_fault+0x41b/0x520
> Call Trace:
>   tdp_page_fault+0xfb/0x290
>   kvm_mmu_page_fault+0x61/0x120
>   handle_ept_misconfig+0x1ba/0x1c0
>   vmx_handle_exit+0xb8/0xd70
>   ? kvm_arch_vcpu_ioctl_run+0x9b6/0x18e0
>   kvm_arch_vcpu_ioctl_run+0xa5a/0x18e0
>   ? kvm_arch_vcpu_load+0x62/0x230
>   kvm_vcpu_ioctl+0x340/0x6c0
>   ? kvm_vcpu_ioctl+0x340/0x6c0
>   ? lock_acquire+0xf5/0x1f0
>   do_vfs_ioctl+0xa2/0x670
>   ? __fget+0x107/0x200
>   SyS_ioctl+0x79/0x90
>   entry_SYSCALL_64_fastpath+0x23/0xc2
> 
> Signed-off-by: Changbin Du <changbin.du@...mail.com>
> Signed-off-by: Changbin Du <changbin.du@...el.com>
> ---
>  arch/x86/kvm/mmu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 9d3f275..d6b2b27 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -3201,7 +3201,7 @@ static bool fast_page_fault(struct kvm_vcpu *vcpu, gva_t gva, int level,
>  
>  		new_spte = spte;
>  
> -		if (is_access_track_spte(spte))
> +		if (!is_mmio_spte(spte) && is_access_track_spte(spte))
>  			new_spte = restore_acc_track_spte(new_spte);
>  
>  		/*
> -- 
> 2.7.4
> 

-- 
Thanks,
Changbin Du

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