Re: [tip:x86/asm] x86/umip: Add emulation code for UMIP instructions
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- Subject: Re: [tip:x86/asm] x86/umip: Add emulation code for UMIP instructions
- From: "H. Peter Anvin" <hpa@xxxxxxxxx>
- Date: Wed, 08 Nov 2017 08:38:18 -0800
- Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>, Borislav Petkov <bp@xxxxxxx>, Vlastimil Babka <vbabka@xxxxxxx>, Tony Luck <tony.luck@xxxxxxxxx>, Fenghua Yu <fenghua.yu@xxxxxxxxx>, Josh Poimboeuf <jpoimboe@xxxxxxxxxx>, Borislav Petkov <bp@xxxxxxxxx>, Brian Gerst <brgerst@xxxxxxxxx>, Jonathan Corbet <corbet@xxxxxxx>, "Ravi V. Shankar" <ravi.v.shankar@xxxxxxxxx>, ricardo.neri-calderon@xxxxxxxxxxxxxxx, Chris Metcalf <cmetcalf@xxxxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>, Masami Hiramatsu <mhiramat@xxxxxxxxxx>, Andrew Lutomirski <luto@xxxxxxxxxx>, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>, ray.huang@xxxxxxx, "Michael S. Tsirkin" <mst@xxxxxxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, Peter Zijlstra <peterz@xxxxxxxxxxxxx>, Chen Yucong <slaoub@xxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Jiri Slaby <jslaby@xxxxxxx>, Shuah Khan <shuah@xxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, "linux-tip-commits@xxxxxxxxxxxxxxx"@zytor.com
- In-reply-to: <CA+55aFyzb5D6DfM_1mxcMbuYOaxZWFxqfv7WZS6zdkqnN7+p0A@mail.gmail.com>
- References: <1509935277-22138-8-git-send-email-ricardo.neri-calderon@linux.intel.com> <tip-1e5db223696afa55e6a038fac638f759e1fdcc01@git.kernel.org> <ca980b88-a668-29cc-3f5a-506088473282@redhat.com> <CA+55aFyzb5D6DfM_1mxcMbuYOaxZWFxqfv7WZS6zdkqnN7+p0A@mail.gmail.com>
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<linux-tip-commits@xxxxxxxxxxxxxxx>
From: hpa@xxxxxxxxx
Message-ID: <67A3DB9F-E58D-42B3-BF16-AC59D2FCECC2@xxxxxxxxx>
On November 8, 2017 8:34:45 AM PST, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
>On Wed, Nov 8, 2017 at 8:14 AM, Denys Vlasenko <dvlasenk@xxxxxxxxxx>
>wrote:
>>
>> Can we avoid maintain emulation of these isns, by asking Wine to
>remove
>> their use instead?
>
>If we ask the Wine people to remove the instruction use, that may mean
>that we can avoid the emulation in four or five _years_ once everybody
>has updated.
>
>But it wouldn't mean that we could avoid it today.
>
>We *do* probably want to print a warning about these instructions,
>whether emulated or not. If emulated, we want to print a warning about
>the emulation being expensive (as a nudge to the Wine people to not do
>that), and if _not_ emulated, we'd want to print a warning about why
>people suddenly got a SIGSEGV in case there are programs that use
>those instructions that people didn't even think of.
>
>But make it ratelimit the warning (perhaps at most once every few
>minutes or whatever), so that people won't flood message logs just
>because they have old stupid programs that use those things.
>
> Linus
The real problem is that 16-bit software uses the instructions mostly for stupid reasons, but smsw in particular is used exactly because it is a virtualization hole.
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
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