arm64: kvm: Prevent restoring stale PMSCR_EL1 for vcpu

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@arm.com>
Cc: Christoffer Dall <christoffer.dall@linaro.org>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Will Deacon <will.deacon@arm.com>
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/kvm/hyp/debug-sr.c b/arch/arm64/kvm/hyp/debug-sr.c
index f5154ed..2add226 100644 (file)
--- 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_nvhe(u64 *pmscr_el1)
 {
        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))