linux-kernel - [tip:x86/hyperv] x86/hyper-v: Check for VP_INVAL in hyperv_flush_tlb

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Message-ID: <tip-110d2a7fc39725d2c29d2fede4f34a35a4f98882@git.kernel.org>
Date:   Mon, 16 Jul 2018 02:25:33 -0700
From:   tip-bot for Vitaly Kuznetsov <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     mikelley@...rosoft.com, tglx@...utronix.de, mingo@...nel.org,
        hpa@...or.com, haiyangz@...rosoft.com, sthemmin@...rosoft.com,
        kys@...rosoft.com, linux-kernel@...r.kernel.org,
        vkuznets@...hat.com, Michael.H.Kelley@...rosoft.com
Subject: [tip:x86/hyperv] x86/hyper-v: Check for VP_INVAL in
 hyperv_flush_tlb_others()

Commit-ID:  110d2a7fc39725d2c29d2fede4f34a35a4f98882
Gitweb:     https://git.kernel.org/tip/110d2a7fc39725d2c29d2fede4f34a35a4f98882
Author:     Vitaly Kuznetsov <vkuznets@...hat.com>
AuthorDate: Mon, 9 Jul 2018 19:40:12 +0200
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Mon, 16 Jul 2018 11:19:49 +0200

x86/hyper-v: Check for VP_INVAL in hyperv_flush_tlb_others()

Commit 1268ed0c474a ("x86/hyper-v: Fix the circular dependency in IPI
 enlightenment") pre-filled hv_vp_index with VP_INVAL so it is now
(theoretically) possible to observe hv_cpu_number_to_vp_number()
returning VP_INVAL. We need to check for that in hyperv_flush_tlb_others().

Not checking for VP_INVAL on the first call site where we do

 if (hv_cpu_number_to_vp_number(cpumask_last(cpus)) >= 64)
                        goto do_ex_hypercall;

is OK, in case we're eligible for non-ex hypercall we'll catch the
issue later in for_each_cpu() cycle and in case we'll be doing ex-
hypercall cpumask_to_vpset() will fail.

It would be nice to change hv_cpu_number_to_vp_number() return
value's type to 'u32' but this will likely be a bigger change as
all call sites need to be checked first.

Fixes: 1268ed0c474a ("x86/hyper-v: Fix the circular dependency in IPI enlightenment")
Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: Michael Kelley <mikelley@...rosoft.com>
Cc: "K. Y. Srinivasan" <kys@...rosoft.com>
Cc: Haiyang Zhang <haiyangz@...rosoft.com>
Cc: Stephen Hemminger <sthemmin@...rosoft.com>
Cc: "Michael Kelley (EOSG)" <Michael.H.Kelley@...rosoft.com>
Cc: devel@...uxdriverproject.org
Cc: "H. Peter Anvin" <hpa@...or.com>
Link: https://lkml.kernel.org/r/20180709174012.17429-3-vkuznets@redhat.com

---
 arch/x86/hyperv/mmu.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/hyperv/mmu.c b/arch/x86/hyperv/mmu.c
index 453d2355cd61..1147e1fed7ff 100644
--- a/arch/x86/hyperv/mmu.c
+++ b/arch/x86/hyperv/mmu.c
@@ -111,6 +111,11 @@ static void hyperv_flush_tlb_others(const struct cpumask *cpus,

 		for_each_cpu(cpu, cpus) {
 			vcpu = hv_cpu_number_to_vp_number(cpu);
+			if (vcpu == VP_INVAL) {
+				local_irq_restore(flags);
+				goto do_native;
+			}
+
 			if (vcpu >= 64)
 				goto do_ex_hypercall;