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From: Paolo Bonzini <pbonzini@redhat.com>
To: Thomas Gleixner <tglx@linutronix.de>,
	LKML <linux-kernel@vger.kernel.org>
Cc: x86@kernel.org, Linus Torvalds <torvalds@linuxfoundation.org>,
	Andy Lutomirski <luto@kernel.org>,
	Stephen Hemminger <stephen@networkplumber.org>,
	Willy Tarreau <w@1wt.eu>, Juergen Gross <jgross@suse.com>,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [patch V2 04/16] x86/tss: Fix and move VMX BUILD_BUG_ON()
Date: Mon, 11 Nov 2019 23:44:19 +0100
Message-ID: <cf3eeec6-8540-2ad8-8d51-17c8f4d4f37b@redhat.com> (raw)
In-Reply-To: <20191111223051.865129706@linutronix.de>

On 11/11/19 23:03, Thomas Gleixner wrote:
> The BUILD_BUG_ON(IO_BITMAP_OFFSET - 1 == 0x67) in the VMX code is bogus in
> two aspects:
> 
> 1) This wants to be in generic x86 code simply to catch issues even when
>    VMX is disabled in Kconfig.
> 
> 2) The IO_BITMAP_OFFSET is not the right thing to check because it makes
>    asssumptions about the layout of tss_struct. Nothing requires that the
>    I/O bitmap is placed right after x86_tss, which is the hardware mandated
>    tss structure. It pointlessly makes restrictions on the struct
>    tss_struct layout.
> 
> The proper thing to check is:
> 
>     - Offset of x86_tss in tss_struct is 0
>     - Size of x86_tss == 0x68
> 
> Move it to the other build time TSS checks and make it do the right thing.
> 
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> ---
> V2: New patch
> ---
>  arch/x86/kvm/vmx/vmx.c       |    8 --------
>  arch/x86/mm/cpu_entry_area.c |    8 ++++++++
>  2 files changed, 8 insertions(+), 8 deletions(-)
> 
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -1338,14 +1338,6 @@ void vmx_vcpu_load_vmcs(struct kvm_vcpu
>  			    (unsigned long)&get_cpu_entry_area(cpu)->tss.x86_tss);
>  		vmcs_writel(HOST_GDTR_BASE, (unsigned long)gdt);   /* 22.2.4 */
>  
> -		/*
> -		 * VM exits change the host TR limit to 0x67 after a VM
> -		 * exit.  This is okay, since 0x67 covers everything except
> -		 * the IO bitmap and have have code to handle the IO bitmap
> -		 * being lost after a VM exit.
> -		 */
> -		BUILD_BUG_ON(IO_BITMAP_OFFSET - 1 != 0x67);
> -
>  		rdmsrl(MSR_IA32_SYSENTER_ESP, sysenter_esp);
>  		vmcs_writel(HOST_IA32_SYSENTER_ESP, sysenter_esp); /* 22.2.3 */
>  
> --- a/arch/x86/mm/cpu_entry_area.c
> +++ b/arch/x86/mm/cpu_entry_area.c
> @@ -161,6 +161,14 @@ static void __init setup_cpu_entry_area(
>  	BUILD_BUG_ON((offsetof(struct tss_struct, x86_tss) ^
>  		      offsetofend(struct tss_struct, x86_tss)) & PAGE_MASK);
>  	BUILD_BUG_ON(sizeof(struct tss_struct) % PAGE_SIZE != 0);
> +	/*
> +	 * VMX changes the host TR limit to 0x67 after a VM exit. This is
> +	 * okay, since 0x67 covers the size of struct x86_hw_tss. Make sure
> +	 * that this is correct.
> +	 */
> +	BUILD_BUG_ON(offsetof(struct tss_struct, x86_tss) != 0);
> +	BUILD_BUG_ON(sizeof(struct x86_hw_tss) != 0x68);
> +
>  	cea_map_percpu_pages(&cea->tss, &per_cpu(cpu_tss_rw, cpu),
>  			     sizeof(struct tss_struct) / PAGE_SIZE, tss_prot);
>  
> 
> 

Acked-by: Paolo Bonzini <pbonzini@redhat.com>


  reply index

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-11 22:03 [patch V2 00/16] x86/iopl: Prevent user space from using CLI/STI with iopl(3) Thomas Gleixner
2019-11-11 22:03 ` [patch V2 01/16] x86/ptrace: Prevent truncation of bitmap size Thomas Gleixner
2019-11-12 15:34   ` Andy Lutomirski
2019-11-11 22:03 ` [patch V2 02/16] x86/process: Unify copy_thread_tls() Thomas Gleixner
2019-11-11 22:03 ` [patch V2 03/16] x86/cpu: Unify cpu_init() Thomas Gleixner
2019-11-11 22:03 ` [patch V2 04/16] x86/tss: Fix and move VMX BUILD_BUG_ON() Thomas Gleixner
2019-11-11 22:44   ` Paolo Bonzini [this message]
2019-11-12 15:37   ` Andy Lutomirski
2019-11-11 22:03 ` [patch V2 05/16] x86/iopl: Cleanup include maze Thomas Gleixner
2019-11-12 15:37   ` Andy Lutomirski
2019-11-11 22:03 ` [patch V2 06/16] x86/io: Speedup schedule out of I/O bitmap user Thomas Gleixner
2019-11-12 16:00   ` Andy Lutomirski
2019-11-12 17:08     ` Thomas Gleixner
2019-11-11 22:03 ` [patch V2 07/16] x86/ioperm: Move iobitmap data into a struct Thomas Gleixner
2019-11-12 16:02   ` Andy Lutomirski
2019-11-12 17:08     ` Thomas Gleixner
2019-11-11 22:03 ` [patch V2 08/16] x86/ioperm: Add bitmap sequence number Thomas Gleixner
2019-11-12  9:22   ` Peter Zijlstra
2019-11-12  9:55     ` [patch V2 08/16] x86/ioperm: Add bitmap sequence numberc Thomas Gleixner
2019-11-12 16:08   ` [patch V2 08/16] x86/ioperm: Add bitmap sequence number Andy Lutomirski
2019-11-12 17:10     ` Thomas Gleixner
2019-11-11 22:03 ` [patch V2 09/16] x86/ioperm: Move TSS bitmap update to exit to user work Thomas Gleixner
2019-11-12 16:16   ` Andy Lutomirski
2019-11-12 17:20     ` Thomas Gleixner
2019-11-12 17:41       ` Andy Lutomirski
2019-11-12 17:46         ` Linus Torvalds
2019-11-13  8:30           ` Peter Zijlstra
2019-11-11 22:03 ` [patch V2 10/16] x86/ioperm: Remove bitmap if all permissions dropped Thomas Gleixner
2019-11-12 17:43   ` Andy Lutomirski
2019-11-11 22:03 ` [patch V2 11/16] x86/ioperm: Share I/O bitmap if identical Thomas Gleixner
2019-11-12  7:14   ` Ingo Molnar
2019-11-12  7:17     ` Thomas Gleixner
2019-11-12  7:52       ` Ingo Molnar
2019-11-12  9:15   ` Peter Zijlstra
2019-11-12  9:51     ` Thomas Gleixner
2019-11-14 11:02     ` David Laight
2019-11-14 12:39       ` Thomas Gleixner
2019-11-14 13:09       ` Peter Zijlstra
2019-11-14 13:22         ` David Laight
2019-11-12 18:12   ` Andy Lutomirski
2019-11-11 22:03 ` [patch V2 12/16] selftests/x86/ioperm: Extend testing so the shared bitmap is exercised Thomas Gleixner
2019-11-11 22:03 ` [patch V2 13/16] x86/iopl: Fixup misleading comment Thomas Gleixner
2019-11-12 18:14   ` Andy Lutomirski
2019-11-11 22:03 ` [patch V2 14/16] x86/iopl: Restrict iopl() permission scope Thomas Gleixner
2019-11-11 23:03   ` Thomas Gleixner
2019-11-12  6:32     ` Ingo Molnar
2019-11-12  8:42   ` Ingo Molnar
2019-11-12 10:07     ` Thomas Gleixner
2019-11-12 18:35   ` Andy Lutomirski
2019-11-11 22:03 ` [patch V2 15/16] x86/iopl: Remove legacy IOPL option Thomas Gleixner
2019-11-12 18:37   ` Andy Lutomirski
2019-11-12 19:40     ` Thomas Gleixner
2019-11-11 22:03 ` [patch V2 16/16] selftests/x86/iopl: Extend test to cover IOPL emulation Thomas Gleixner
2019-11-12  7:40 ` [PATCH] x86/iopl: Factor out IO-bitmap related TSS fields into 'struct x86_io_bitmap' Ingo Molnar
2019-11-12  7:59   ` [PATCH] x86/iopl: Harmonize 'struct io_bitmap' and 'struct x86_io_bitmap' nomenclature Ingo Molnar
2019-11-12  8:11   ` [PATCH] x86/iopl: Clear up the role of the two bitmap copying fields Ingo Molnar
2019-11-12  8:15   ` [PATCH] x86/iopl: Rename <asm/iobitmap.h> to <asm/io_bitmap.h> Ingo Molnar

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