[PATCH v3 13/23] kvm: arm64: Add SMC handler in nVHE EL2

David Brazdil
2020-11-26T15:55:30Z

Add handler of host SMCs in KVM nVHE trap handler. Forward all SMCs to
EL3 and propagate the result back to EL1. This is done in preparation
for validating host SMCs in KVM nVHE protected mode.

The implementation assumes that firmware uses SMCCC v1.2 or older. That
means x0-x17 can be used both for arguments and results, other GPRs are
preserved.

Signed-off-by: David Brazdil <dbrazdil@google.com>
---
arch/arm64/kvm/hyp/nvhe/host.S | 38 ++++++++++++++++++++++++++++++
arch/arm64/kvm/hyp/nvhe/hyp-main.c | 35 ++++++++++++++++++++++++---
2 files changed, 70 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/host.S b/arch/arm64/kvm/hyp/nvhe/host.S
index fe2740b224cf..2b56f0bdf874 100644
--- a/arch/arm64/kvm/hyp/nvhe/host.S
+++ b/arch/arm64/kvm/hyp/nvhe/host.S
@@ -180,3 +180,41 @@ SYM_CODE_START(__kvm_hyp_host_vector)
invalid_host_el1_vect // FIQ 32-bit EL1
invalid_host_el1_vect // Error 32-bit EL1
SYM_CODE_END(__kvm_hyp_host_vector)
+
+/*
+ * Forward SMC with arguments in struct kvm_cpu_context, and
+ * store the result into the same struct. Assumes SMCCC 1.2 or older.
+ *
+ * x0: struct kvm_cpu_context*
+ */
+SYM_CODE_START(__kvm_hyp_host_forward_smc)
+ /*
+ * Use x18 to keep the pointer to the host context because
+ * x18 is callee-saved in SMCCC but not in AAPCS64.
+ */
+ mov x18, x0
+
+ ldp x0, x1, [x18, #CPU_XREG_OFFSET(0)]
+ ldp x2, x3, [x18, #CPU_XREG_OFFSET(2)]
+ ldp x4, x5, [x18, #CPU_XREG_OFFSET(4)]
+ ldp x6, x7, [x18, #CPU_XREG_OFFSET(6)]
+ ldp x8, x9, [x18, #CPU_XREG_OFFSET(8)]
+ ldp x10, x11, [x18, #CPU_XREG_OFFSET(10)]
+ ldp x12, x13, [x18, #CPU_XREG_OFFSET(12)]
+ ldp x14, x15, [x18, #CPU_XREG_OFFSET(14)]
+ ldp x16, x17, [x18, #CPU_XREG_OFFSET(16)]
+
+ smc #0
+
+ stp x0, x1, [x18, #CPU_XREG_OFFSET(0)]
+ stp x2, x3, [x18, #CPU_XREG_OFFSET(2)]
+ stp x4, x5, [x18, #CPU_XREG_OFFSET(4)]
+ stp x6, x7, [x18, #CPU_XREG_OFFSET(6)]
+ stp x8, x9, [x18, #CPU_XREG_OFFSET(8)]
+ stp x10, x11, [x18, #CPU_XREG_OFFSET(10)]
+ stp x12, x13, [x18, #CPU_XREG_OFFSET(12)]
+ stp x14, x15, [x18, #CPU_XREG_OFFSET(14)]
+ stp x16, x17, [x18, #CPU_XREG_OFFSET(16)]
+
+ ret
+SYM_CODE_END(__kvm_hyp_host_forward_smc)
diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
index a4f1cac714d7..f25680ede080 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
@@ -18,6 +18,8 @@

DEFINE_PER_CPU(struct kvm_nvhe_init_params, kvm_init_params);

+void __kvm_hyp_host_forward_smc(struct kvm_cpu_context *host_ctxt);
+
static void handle___kvm_vcpu_run(struct kvm_cpu_context *host_ctxt)
{
DECLARE_REG(struct kvm_vcpu *, vcpu, host_ctxt, 1);
@@ -152,12 +154,39 @@ static void handle_host_hcall(struct kvm_cpu_context *host_ctxt)
cpu_reg(host_ctxt, 0) = SMCCC_RET_NOT_SUPPORTED;
}

+static void default_host_smc_handler(struct kvm_cpu_context *host_ctxt)
+{
+ __kvm_hyp_host_forward_smc(host_ctxt);
+}
+
+static void skip_host_instruction(void)
+{
+ write_sysreg_el2(read_sysreg_el2(SYS_ELR) + 4, SYS_ELR);
+}
+
+static void handle_host_smc(struct kvm_cpu_context *host_ctxt)
+{
+ default_host_smc_handler(host_ctxt);
+
+ /*
+ * Unlike HVC, the return address of an SMC is the instruction's PC.
+ * Move the return address past the instruction.
+ */
+ skip_host_instruction();
+}
+
void handle_trap(struct kvm_cpu_context *host_ctxt)
{
u64 esr = read_sysreg_el2(SYS_ESR);

- if (unlikely(ESR_ELx_EC(esr) != ESR_ELx_EC_HVC64))
+ switch (ESR_ELx_EC(esr)) {
+ case ESR_ELx_EC_HVC64:
+ handle_host_hcall(host_ctxt);
+ break;
+ case ESR_ELx_EC_SMC64:
+ handle_host_smc(host_ctxt);
+ break;
+ default:
hyp_panic();
-
- handle_host_hcall(host_ctxt);
+ }
}
--
2.29.2.454.gaff20da3a2-goog