Re: [PATCH v1 08/24] kvm: arm64: Move hyp-init params to a per-CPU struct

From: Marc Zyngier
Date: Tue Nov 10 2020 - 10:30:27 EST

On 2020-11-09 11:32, David Brazdil wrote:
Once we start initializing KVM on newly booted cores before the rest of
the kernel, parameters to __do_hyp_init will need to be provided by EL2
rather than EL1. At that point it will not be possible to pass its four
arguments directly because PSCI_CPU_ON only supports one context
argument.

Refactor __do_hyp_init to accept its parameters in a struct. This
prepares the code for KVM booting cores as well as removes any limits on
the number of __do_hyp_init arguments.

Signed-off-by: David Brazdil <dbrazdil@xxxxxxxxxx>
---
arch/arm64/include/asm/kvm_asm.h | 7 +++++++
arch/arm64/include/asm/kvm_hyp.h | 4 ++++
arch/arm64/kernel/asm-offsets.c | 4 ++++
arch/arm64/kvm/arm.c | 26 ++++++++++++++------------
arch/arm64/kvm/hyp/nvhe/hyp-init.S | 21 ++++++++++-----------
arch/arm64/kvm/hyp/nvhe/hyp-main.c | 2 ++
6 files changed, 41 insertions(+), 23 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
index 54387ccd1ab2..a49a87a186c3 100644
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -150,6 +150,13 @@ extern void *__vhe_undefined_symbol;

#endif

+struct kvm_nvhe_init_params {
+ phys_addr_t pgd_ptr;
+ unsigned long tpidr_el2;
+ unsigned long hyp_stack_ptr;
+ unsigned long vector_ptr;
+};

Please add some documentation here, specially indicating what address space
the values are relative to.

+
/* Translate a kernel address @ptr into its equivalent linear mapping */
#define kvm_ksym_ref(ptr) \
({ \
diff --git a/arch/arm64/include/asm/kvm_hyp.h b/arch/arm64/include/asm/kvm_hyp.h
index 6b664de5ec1f..a3289071f3d8 100644
--- a/arch/arm64/include/asm/kvm_hyp.h
+++ b/arch/arm64/include/asm/kvm_hyp.h
@@ -15,6 +15,10 @@
DECLARE_PER_CPU(struct kvm_cpu_context, kvm_hyp_ctxt);
DECLARE_PER_CPU(unsigned long, kvm_hyp_vector);

+#ifdef __KVM_NVHE_HYPERVISOR__
+DECLARE_PER_CPU(struct kvm_nvhe_init_params, kvm_init_params);
+#endif
+
#define read_sysreg_elx(r,nvh,vh) \
({ \
u64 reg; \
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index 7d32fc959b1a..0cbb86135c7c 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -110,6 +110,10 @@ int main(void)
DEFINE(CPU_APGAKEYLO_EL1, offsetof(struct kvm_cpu_context,
sys_regs[APGAKEYLO_EL1]));
DEFINE(HOST_CONTEXT_VCPU, offsetof(struct kvm_cpu_context,
__hyp_running_vcpu));
DEFINE(HOST_DATA_CONTEXT, offsetof(struct kvm_host_data, host_ctxt));
+ DEFINE(NVHE_INIT_PGD_PTR, offsetof(struct kvm_nvhe_init_params, pgd_ptr));
+ DEFINE(NVHE_INIT_TPIDR_EL2, offsetof(struct kvm_nvhe_init_params,
tpidr_el2));
+ DEFINE(NVHE_INIT_STACK_PTR, offsetof(struct kvm_nvhe_init_params,
hyp_stack_ptr));
+ DEFINE(NVHE_INIT_VECTOR_PTR, offsetof(struct kvm_nvhe_init_params,
vector_ptr));
#endif
#ifdef CONFIG_CPU_PM
DEFINE(CPU_CTX_SP, offsetof(struct cpu_suspend_ctx, sp));
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index b85b4294b72d..1a57b6025937 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -50,6 +50,7 @@ DECLARE_KVM_HYP_PER_CPU(unsigned long, kvm_hyp_vector);

static DEFINE_PER_CPU(unsigned long, kvm_arm_hyp_stack_page);
unsigned long kvm_arm_hyp_percpu_base[NR_CPUS];
+DECLARE_KVM_NVHE_PER_CPU(struct kvm_nvhe_init_params, kvm_init_params);

/* The VMID used in the VTTBR */
static atomic64_t kvm_vmid_gen = ATOMIC64_INIT(1);
@@ -1331,10 +1332,7 @@ static int kvm_map_vectors(void)

static void cpu_init_hyp_mode(void)
{
- phys_addr_t pgd_ptr;
- unsigned long hyp_stack_ptr;
- unsigned long vector_ptr;
- unsigned long tpidr_el2;
+ struct kvm_nvhe_init_params *params = this_cpu_ptr_nvhe_sym(kvm_init_params);
struct arm_smccc_res res;

/* Switch from the HYP stub to our own HYP init vector */
@@ -1345,13 +1343,18 @@ static void cpu_init_hyp_mode(void)
* kernel's mapping to the linear mapping, and store it in tpidr_el2
* so that we can use adr_l to access per-cpu variables in EL2.
*/
- tpidr_el2 = (unsigned long)this_cpu_ptr_nvhe_sym(__per_cpu_start) -
- (unsigned long)kvm_ksym_ref(CHOOSE_NVHE_SYM(__per_cpu_start));
+ params->tpidr_el2 = (unsigned long)this_cpu_ptr_nvhe_sym(__per_cpu_start) -
+ (unsigned long)kvm_ksym_ref(CHOOSE_NVHE_SYM(__per_cpu_start));

- pgd_ptr = kvm_mmu_get_httbr();
- hyp_stack_ptr = __this_cpu_read(kvm_arm_hyp_stack_page) + PAGE_SIZE;
- hyp_stack_ptr = kern_hyp_va(hyp_stack_ptr);
- vector_ptr = (unsigned long)kern_hyp_va(kvm_ksym_ref(__kvm_hyp_host_vector));
+ params->pgd_ptr = kvm_mmu_get_httbr();
+ params->vector_ptr = (unsigned
long)kern_hyp_va(kvm_ksym_ref(__kvm_hyp_host_vector));
+ params->hyp_stack_ptr =
kern_hyp_va(__this_cpu_read(kvm_arm_hyp_stack_page) + PAGE_SIZE);
+
+ /*
+ * Flush the init params from the data cache because the struct will
+ * be read from while the MMU is off.

s/from while/while/ ?

+ */
+ __flush_dcache_area(params, sizeof(*params));

/*
* Call initialization code, and switch to the full blown HYP code.
@@ -1360,8 +1363,7 @@ static void cpu_init_hyp_mode(void)
* cpus_have_const_cap() wrapper.
*/
BUG_ON(!system_capabilities_finalized());
- arm_smccc_1_1_hvc(KVM_HOST_SMCCC_FUNC(__kvm_hyp_init),
- pgd_ptr, tpidr_el2, hyp_stack_ptr, vector_ptr, &res);
+ arm_smccc_1_1_hvc(KVM_HOST_SMCCC_FUNC(__kvm_hyp_init),
virt_to_phys(params), &res);
WARN_ON(res.a0 != SMCCC_RET_SUCCESS);

/*
diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-init.S
b/arch/arm64/kvm/hyp/nvhe/hyp-init.S
index 96e70f976ff5..6f3ac5d428ec 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-init.S
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-init.S
@@ -47,10 +47,7 @@ __invalid:

/*
* x0: SMCCC function ID
- * x1: HYP pgd
- * x2: per-CPU offset
- * x3: HYP stack
- * x4: HYP vectors
+ * x1: struct kvm_nvhe_init_params PA
*/
__do_hyp_init:
/* Check for a stub HVC call */
@@ -71,10 +68,16 @@ __do_hyp_init:
mov x0, #SMCCC_RET_NOT_SUPPORTED
eret

-1:
- /* Set tpidr_el2 for use by HYP to free a register */
- msr tpidr_el2, x2
+1: ldr x0, [x1, #NVHE_INIT_TPIDR_EL2]
+ msr tpidr_el2, x0

+ ldr x0, [x1, #NVHE_INIT_STACK_PTR]
+ mov sp, x0
+
+ ldr x0, [x1, #NVHE_INIT_VECTOR_PTR]
+ msr vbar_el2, x0
+
+ ldr x1, [x1, #NVHE_INIT_PGD_PTR]
phys_to_ttbr x0, x1
alternative_if ARM64_HAS_CNP
orr x0, x0, #TTBR_CNP_BIT
@@ -134,10 +137,6 @@ alternative_else_nop_endif
msr sctlr_el2, x0
isb

- /* Set the stack and new vectors */
- mov sp, x3
- msr vbar_el2, x4
-
/* Hello, World! */
mov x0, #SMCCC_RET_SUCCESS
eret
diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
index e2eafe2c93af..411b0f652417 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
@@ -14,6 +14,8 @@

#include <kvm/arm_hypercalls.h>

+DEFINE_PER_CPU(struct kvm_nvhe_init_params, kvm_init_params);
+
static void handle_host_hcall(unsigned long func_id,
struct kvm_cpu_context *host_ctxt)
{

Thanks,

M.
--
Jazz is not dead. It just smells funny...