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Message-ID: <CAG48ez0aTJMREb1JL6SaT5rNLs6oUZVevj+BGrUzVEprZNFKOw@mail.gmail.com> Date: Fri, 12 Oct 2018 15:25:46 +0200 From: Jann Horn <jannh@...gle.com> To: sneves@....uc.pt Cc: Andy Lutomirski <luto@...nel.org>, kristen@...ux.intel.com, Kernel Hardening <kernel-hardening@...ts.openwall.com>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, "H . Peter Anvin" <hpa@...or.com>, "the arch/x86 maintainers" <x86@...nel.org>, kernel list <linux-kernel@...r.kernel.org> Subject: Re: [PATCH] x86: entry: flush the cache if syscall error On Fri, Oct 12, 2018 at 11:41 AM Samuel Neves <sneves@....uc.pt> wrote: > > On Thu, Oct 11, 2018 at 8:25 PM Andy Lutomirski <luto@...nel.org> wrote: > > What exactly is this trying to protect against? And how many cycles > > should we expect L1D_FLUSH to take? > > As far as I could measure, I got 1660 cycles per wrmsr 0x10b, 0x1 on a > Skylake chip, and 1220 cycles on a Skylake-SP. Is that with L1D mostly empty, with L1D mostly full with clean lines, or with L1D full of dirty lines that need to be written back?
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