Hi Zenghui,
Thanks for having a go at the backport.
On Tue, 01 Jun 2021 12:12:37 +0100, Zenghui Yu yuzenghui@huawei.com wrote:
From: Marc Zyngier maz@kernel.org
commit 26778aaa134a9aefdf5dbaad904054d7be9d656d upstream.
KVM currently updates PC (and the corresponding exception state) using a two phase approach: first by setting a set of flags, then by converting these flags into a state update when the vcpu is about to enter the guest.
However, this creates a disconnect with userspace if the vcpu thread returns there with any exception/PC flag set. In this case, the exposed context is wrong, as userspace doesn't have access to these flags (they aren't architectural). It also means that these flags are preserved across a reset, which isn't expected.
To solve this problem, force an explicit synchronisation of the exception state on vcpu exit to userspace. As an optimisation for nVHE systems, only perform this when there is something pending.
Reported-by: Zenghui Yu yuzenghui@huawei.com Reviewed-by: Alexandru Elisei alexandru.elisei@arm.com Reviewed-by: Zenghui Yu yuzenghui@huawei.com Tested-by: Zenghui Yu yuzenghui@huawei.com Signed-off-by: Marc Zyngier maz@kernel.org Cc: stable@vger.kernel.org # 5.11 [yuz: stable-5.12.y backport: add __KVM_HOST_SMCCC_FUNC___kvm_adjust_pc macro manually and keep it consistent with mainline]
I'd rather you allocated a new number here, irrespective of what mainline has (rational below).
Signed-off-by: Zenghui Yu yuzenghui@huawei.com
arch/arm64/include/asm/kvm_asm.h | 1 + arch/arm64/kvm/arm.c | 11 +++++++++++ arch/arm64/kvm/hyp/exception.c | 4 ++-- arch/arm64/kvm/hyp/nvhe/hyp-main.c | 8 ++++++++ 4 files changed, 22 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h index a8578d650bb6..d7f769bb6c9c 100644 --- a/arch/arm64/include/asm/kvm_asm.h +++ b/arch/arm64/include/asm/kvm_asm.h @@ -57,6 +57,7 @@ #define __KVM_HOST_SMCCC_FUNC___kvm_get_mdcr_el2 12 #define __KVM_HOST_SMCCC_FUNC___vgic_v3_save_aprs 13 #define __KVM_HOST_SMCCC_FUNC___vgic_v3_restore_aprs 14 +#define __KVM_HOST_SMCCC_FUNC___kvm_adjust_pc 21
This is going to generate a larger than necessary host_hcall array in hyp/nvhe/hyp-main.c, which we're trying to keep tightly packed for obvious reasons.
With this nit fixed:
Reviewed-by: Marc Zyngier maz@kernel.org
Thanks,
M.