From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: speck@linutronix.de
Subject: [MODERATED] Re: [PATCH v4 8/8] [PATCH v4 8/8] Linux Patch #8
Date: Thu, 28 Jun 2018 12:40:48 -0400 [thread overview]
Message-ID: <20180628164047.GA3445@char.US.ORACLE.com> (raw)
In-Reply-To: <alpine.DEB.2.21.1806271853470.17787@nanos.tec.linutronix.de>
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -194,6 +194,14 @@ module_param(ple_window_max, uint, 0444)
>
> extern const ulong vmx_return;
>
> +static DEFINE_STATIC_KEY_FALSE(vmx_l1d_should_flush);
> +
> +enum vmx_l1d_flush_state {
> + VMENTER_L1D_FLUSH_NEVER,
> + VMENTER_L1D_FLUSH_COND,
> + VMENTER_L1D_FLUSH_ALWAYS,
> +};
> +
> struct kvm_vmx {
> struct kvm kvm;
>
> @@ -2653,38 +2661,10 @@ static void vmx_prepare_guest_switch(str
> {
> vmx_save_host_state(vcpu);
>
> - if (!enable_ept || static_cpu_has(X86_FEATURE_HYPERVISOR) ||
> - !static_cpu_has(X86_BUG_L1TF)) {
> - vcpu->arch.flush_cache_req = false;
> - return;
> - }
> + if (static_branch_unlikely(&vmx_l1d_should_flush)) {
> + bool force = vmentry_l1d_flush == VMENTER_L1D_FLUSH_ALWAYS;
>
> - switch (vmentry_l1d_flush) {
> - case 0:
> - vcpu->arch.flush_cache_req = false;
> - break;
> - case 1:
> - /*
> - * If vmentry_l1d_flush is 1, each vmexit handler is responsible for
> - * setting vcpu->arch.vcpu_unconfined. Currently this happens in the
> - * following cases:
> - * - vmlaunch/vmresume: we do not want the cache to be cleared by a
> - * nested hypervisor *and* by KVM on bare metal, so we just do it
> - * on every nested entry. Nested hypervisors do not bother clearing
> - * the cache.
> - * - anything that runs the emulator (the slow paths for EPT misconfig
> - * or I/O instruction)
> - * - anything that can cause get_user_pages (EPT violation, and again
> - * the slow paths for EPT misconfig or I/O instruction)
> - * - anything that can run code outside KVM (external interrupt,
> - * which can run interrupt handlers or irqs; or the sched_in
> - * preempt notifier)
> - */
> - break;
> - case 2:
> - default:
> - vcpu->arch.flush_cache_req = true;
> - break;
> + vcpu->arch.flush_cache_req = force;
This ought to be:
if (force)
vcpu->arch.flush_cache_req = force;
or perhaps:
if (vmentry_l1d_flush == VMENTER_L1D_FLUSH_ALWAYS)
vcpu->arch.flush_cache_req = true;
The problem is that if we are in 'vmentry_l1d_flush=1' we should
not modify vcpu->arch.flush_cache_req as the vcpu_enter_guest does:
7464
7465 vcpu->arch.flush_cache_req = vcpu->arch.vcpu_unconfined; <===
7466 kvm_x86_ops->prepare_guest_switch(vcpu);
7467 vcpu->arch.vcpu_unconfined = false;
7468 if (vcpu->arch.flush_cache_req)
7469 vcpu->stat.l1d_flush++;
Rethinking this, maybe rip the above from vcpu_enter_guest and in this function
will do:
vcpu->arch.flush_cache_req = (vmentry_l1d_flush == VMENTER_L1D_FLUSH_ALWAYS) ? true : vcpu->arch.vcpu_unconfined;
or so?
Let me try that out.
prev parent reply other threads:[~2018-06-28 16:41 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-23 13:54 [MODERATED] [PATCH v4 8/8] [PATCH v4 8/8] Linux Patch #8 konrad.wilk
2018-06-25 14:32 ` [MODERATED] " Paolo Bonzini
2018-06-27 13:05 ` Thomas Gleixner
2018-06-27 14:43 ` [MODERATED] " Konrad Rzeszutek Wilk
2018-06-27 17:00 ` Thomas Gleixner
2018-06-28 16:40 ` Konrad Rzeszutek Wilk [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20180628164047.GA3445@char.US.ORACLE.com \
--to=konrad.wilk@oracle.com \
--cc=speck@linutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).