linux-kernel - [PATCH 4.14 57/74] arm64: kvm: Prevent restoring stale PMSCR

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Date:   Wed, 27 Dec 2017 17:46:30 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Julien Thierry <julien.thierry@....com>,
        Christoffer Dall <christoffer.dall@...aro.org>,
        Marc Zyngier <marc.zyngier@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>
Subject: [PATCH 4.14 57/74] arm64: kvm: Prevent restoring stale PMSCR_EL1 for vcpu

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Julien Thierry <julien.thierry@....com>

commit bfe766cf65fb65e68c4764f76158718560bdcee5 upstream.

When VHE is not present, KVM needs to save and restores PMSCR_EL1 when
possible. If SPE is used by the host, value of PMSCR_EL1 cannot be saved
for the guest.
If the host starts using SPE between two save+restore on the same vcpu,
restore will write the value of PMSCR_EL1 read during the first save.

Make sure __debug_save_spe_nvhe clears the value of the saved PMSCR_EL1
when the guest cannot use SPE.

Signed-off-by: Julien Thierry <julien.thierry@....com>
Cc: Christoffer Dall <christoffer.dall@...aro.org>
Cc: Marc Zyngier <marc.zyngier@....com>
Cc: Catalin Marinas <catalin.marinas@....com>
Reviewed-by: Will Deacon <will.deacon@....com>
Reviewed-by: Christoffer Dall <christoffer.dall@...aro.org>
Signed-off-by: Christoffer Dall <christoffer.dall@...aro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/arm64/kvm/hyp/debug-sr.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/arch/arm64/kvm/hyp/debug-sr.c
+++ b/arch/arm64/kvm/hyp/debug-sr.c
@@ -84,6 +84,9 @@ static void __hyp_text __debug_save_spe_
 {
 	u64 reg;
 
+	/* Clear pmscr in case of early return */
+	*pmscr_el1 = 0;
+
 	/* SPE present on this CPU? */
 	if (!cpuid_feature_extract_unsigned_field(read_sysreg(id_aa64dfr0_el1),
 						  ID_AA64DFR0_PMSVER_SHIFT))