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 Cc: Will Deacon will.deacon@arm.com Cc: stable@vger.kernel.org --- arch/arm64/kvm/hyp/debug-sr.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/arch/arm64/kvm/hyp/debug-sr.c b/arch/arm64/kvm/hyp/debug-sr.c index 321c9c0..f4363d4 100644 --- a/arch/arm64/kvm/hyp/debug-sr.c +++ b/arch/arm64/kvm/hyp/debug-sr.c @@ -74,6 +74,9 @@ 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)) -- 1.9.1
On Wed, Dec 06, 2017 at 05:09:49PM +0000, Julien Thierry wrote:
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.
Ok, so the problem is that we have a stale (non-zero) saved pmscr_el1, and therefore the restore code unconditionally restores that even though SPE is no longer in use by the host. Well spotted!
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 Cc: Will Deacon will.deacon@arm.com Cc: stable@vger.kernel.org
arch/arm64/kvm/hyp/debug-sr.c | 3 +++ 1 file changed, 3 insertions(+)
Reviewed-by: Will Deacon will.deacon@arm.com
Will
On Wed, Dec 06, 2017 at 05:09:49PM +0000, Julien Thierry wrote:
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 Cc: Will Deacon will.deacon@arm.com Cc: stable@vger.kernel.org
arch/arm64/kvm/hyp/debug-sr.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/arch/arm64/kvm/hyp/debug-sr.c b/arch/arm64/kvm/hyp/debug-sr.c index 321c9c0..f4363d4 100644 --- a/arch/arm64/kvm/hyp/debug-sr.c +++ b/arch/arm64/kvm/hyp/debug-sr.c @@ -74,6 +74,9 @@ 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))
-- 1.9.1
Applied, thanks. -Christoffer
linux-stable-mirror@lists.linaro.org
-
Christoffer Dall -
Julien Thierry -
Will Deacon