From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
x86@kernel.org, linux-arch@vger.kernel.org,
Will Deacon <will@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
Mark Rutland <mark.rutland@arm.com>,
Kees Cook <keescook@chromium.org>,
Keno Fischer <keno@juliacomputing.com>,
Paolo Bonzini <pbonzini@redhat.com>,
kvm@vger.kernel.org,
Gabriel Krisman Bertazi <krisman@collabora.com>
Subject: Re: [patch V5 08/15] x86/entry: Move user return notifier out of loop
Date: Thu, 23 Jul 2020 16:41:11 -0700 [thread overview]
Message-ID: <20200723234111.GJ21891@linux.intel.com> (raw)
In-Reply-To: <20200722220520.159112003@linutronix.de>
On Thu, Jul 23, 2020 at 12:00:02AM +0200, Thomas Gleixner wrote:
> From: Thomas Gleixner <tglx@linutronix.de>
>
> Guests and user space share certain MSRs. KVM sets these MSRs to guest
> values once and does not set them back to user space values on every VM
> exit to spare the costly MSR operations.
>
> User return notifiers ensure that these MSRs are set back to the correct
> values before returning to user space in exit_to_usermode_loop().
>
> There is no reason to evaluate the TIF flag indicating that user return
> notifiers need to be invoked in the loop. The important point is that they
> are invoked before returning to user space.
>
> Move the invocation out of the loop into the section which does the last
> preperatory steps before returning to user space. That section is not
> preemptible and runs with interrupts disabled until the actual return.
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-and-tested-by: Sean Christopherson <sean.j.christopherson@intel.com>
next prev parent reply other threads:[~2020-07-23 23:41 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-22 21:59 [patch V5 00/15] entry, x86, kvm: Generic entry/exit functionality for host and guest Thomas Gleixner
2020-07-22 21:59 ` Thomas Gleixner
2020-07-22 21:59 ` [patch V5 01/15] seccomp: Provide stub for __secure_computing() Thomas Gleixner
2020-07-22 21:59 ` Thomas Gleixner
2020-07-22 21:59 ` [patch V5 02/15] entry: Provide generic syscall entry functionality Thomas Gleixner
2020-07-22 21:59 ` Thomas Gleixner
2020-07-22 21:59 ` [patch V5 03/15] entry: Provide generic syscall exit function Thomas Gleixner
2020-07-22 21:59 ` [patch V5 04/15] entry: Provide generic interrupt entry/exit code Thomas Gleixner
2020-07-22 21:59 ` Thomas Gleixner
2020-07-22 21:59 ` [patch V5 05/15] entry: Provide infrastructure for work before transitioning to guest mode Thomas Gleixner
2020-07-29 16:55 ` Qian Cai
2020-07-29 16:55 ` Qian Cai
2020-07-30 7:19 ` Thomas Gleixner
2020-07-22 22:00 ` [patch V5 06/15] x86/entry: Consolidate check_user_regs() Thomas Gleixner
2020-07-22 22:00 ` Thomas Gleixner
2020-07-22 22:00 ` [patch V5 07/15] x86/entry: Consolidate 32/64 bit syscall entry Thomas Gleixner
2020-07-22 22:00 ` [patch V5 08/15] x86/entry: Move user return notifier out of loop Thomas Gleixner
2020-07-23 23:41 ` Sean Christopherson [this message]
2020-07-22 22:00 ` [patch V5 09/15] x86/ptrace: Provide pt_regs helper for entry/exit Thomas Gleixner
2020-07-22 22:00 ` [patch V5 10/15] x86/entry: Use generic syscall entry function Thomas Gleixner
2020-07-22 22:00 ` Thomas Gleixner
2020-07-22 22:00 ` [patch V5 11/15] x86/entry: Use generic syscall exit functionality Thomas Gleixner
2020-07-22 22:00 ` Thomas Gleixner
2020-07-22 22:00 ` [patch V5 12/15] x86/entry: Cleanup idtentry_entry/exit_user Thomas Gleixner
2020-07-22 22:00 ` Thomas Gleixner
2020-07-22 22:00 ` [patch V5 13/15] x86/entry: Use generic interrupt entry/exit code Thomas Gleixner
2020-07-22 22:00 ` Thomas Gleixner
2020-07-24 14:28 ` Ingo Molnar
2020-07-22 22:00 ` [patch V5 14/15] x86/entry: Cleanup idtentry_enter/exit Thomas Gleixner
2020-07-22 22:00 ` [patch V5 15/15] x86/kvm: Use generic xfer to guest work function Thomas Gleixner
2020-07-24 0:17 ` Sean Christopherson
2020-07-24 0:46 ` Thomas Gleixner
2020-07-24 0:55 ` Sean Christopherson
2020-07-24 14:24 ` Ingo Molnar
2020-07-24 19:08 ` Thomas Gleixner
2020-07-24 20:51 ` [patch V5 00/15] entry, x86, kvm: Generic entry/exit functionality for host and guest Thomas Gleixner
2020-07-24 20:51 ` Thomas Gleixner
2020-07-29 13:39 ` Steven Price
2020-07-29 13:39 ` Steven Price
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