KVM: arm64: Handle FFA_RXTX_MAP and FFA_RXTX_UNMAP calls from the host

Handle FFA_RXTX_MAP and FFA_RXTX_UNMAP calls from the host by sharing
the host's mailbox memory with the hypervisor and establishing a
separate pair of mailboxes between the hypervisor and the SPMD at EL3.

Co-developed-by: Andrew Walbran <qwandor@google.com>
Signed-off-by: Andrew Walbran <qwandor@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20230523101828.7328-5-will@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
index c85e5d4..0c020cd 100644 (file)
--- a/arch/arm64/kvm/hyp/nvhe/ffa.c
+++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
@@ -31,6 +31,8 @@
 #include <asm/kvm_pkvm.h>
 
 #include <nvhe/ffa.h>
+#include <nvhe/mem_protect.h>
+#include <nvhe/memory.h>
 #include <nvhe/trap_handler.h>
 #include <nvhe/spinlock.h>
 
@@ -52,6 +54,7 @@ struct kvm_ffa_buffers {
  * client.
  */
 static struct kvm_ffa_buffers hyp_buffers;
+static struct kvm_ffa_buffers host_buffers;
 
 static void ffa_to_smccc_error(struct arm_smccc_res *res, u64 ffa_errno)
 {
@@ -61,6 +64,15 @@ static void ffa_to_smccc_error(struct arm_smccc_res *res, u64 ffa_errno)
        };
 }
 
+static void ffa_to_smccc_res(struct arm_smccc_res *res, int ret)
+{
+       if (ret == FFA_RET_SUCCESS) {
+               *res = (struct arm_smccc_res) { .a0 = FFA_SUCCESS };
+       } else {
+               ffa_to_smccc_error(res, ret);
+       }
+}
+
 static void ffa_set_retval(struct kvm_cpu_context *ctxt,
                           struct arm_smccc_res *res)
 {
@@ -78,6 +90,144 @@ static bool is_ffa_call(u64 func_id)
               ARM_SMCCC_FUNC_NUM(func_id) <= FFA_MAX_FUNC_NUM;
 }
 
+static int ffa_map_hyp_buffers(u64 ffa_page_count)
+{
+       struct arm_smccc_res res;
+
+       arm_smccc_1_1_smc(FFA_FN64_RXTX_MAP,
+                         hyp_virt_to_phys(hyp_buffers.tx),
+                         hyp_virt_to_phys(hyp_buffers.rx),
+                         ffa_page_count,
+                         0, 0, 0, 0,
+                         &res);
+
+       return res.a0 == FFA_SUCCESS ? FFA_RET_SUCCESS : res.a2;
+}
+
+static int ffa_unmap_hyp_buffers(void)
+{
+       struct arm_smccc_res res;
+
+       arm_smccc_1_1_smc(FFA_RXTX_UNMAP,
+                         HOST_FFA_ID,
+                         0, 0, 0, 0, 0, 0,
+                         &res);
+
+       return res.a0 == FFA_SUCCESS ? FFA_RET_SUCCESS : res.a2;
+}
+
+static void do_ffa_rxtx_map(struct arm_smccc_res *res,
+                           struct kvm_cpu_context *ctxt)
+{
+       DECLARE_REG(phys_addr_t, tx, ctxt, 1);
+       DECLARE_REG(phys_addr_t, rx, ctxt, 2);
+       DECLARE_REG(u32, npages, ctxt, 3);
+       int ret = 0;
+       void *rx_virt, *tx_virt;
+
+       if (npages != (KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE) / FFA_PAGE_SIZE) {
+               ret = FFA_RET_INVALID_PARAMETERS;
+               goto out;
+       }
+
+       if (!PAGE_ALIGNED(tx) || !PAGE_ALIGNED(rx)) {
+               ret = FFA_RET_INVALID_PARAMETERS;
+               goto out;
+       }
+
+       hyp_spin_lock(&host_buffers.lock);
+       if (host_buffers.tx) {
+               ret = FFA_RET_DENIED;
+               goto out_unlock;
+       }
+
+       /*
+        * Map our hypervisor buffers into the SPMD before mapping and
+        * pinning the host buffers in our own address space.
+        */
+       ret = ffa_map_hyp_buffers(npages);
+       if (ret)
+               goto out_unlock;
+
+       ret = __pkvm_host_share_hyp(hyp_phys_to_pfn(tx));
+       if (ret) {
+               ret = FFA_RET_INVALID_PARAMETERS;
+               goto err_unmap;
+       }
+
+       ret = __pkvm_host_share_hyp(hyp_phys_to_pfn(rx));
+       if (ret) {
+               ret = FFA_RET_INVALID_PARAMETERS;
+               goto err_unshare_tx;
+       }
+
+       tx_virt = hyp_phys_to_virt(tx);
+       ret = hyp_pin_shared_mem(tx_virt, tx_virt + 1);
+       if (ret) {
+               ret = FFA_RET_INVALID_PARAMETERS;
+               goto err_unshare_rx;
+       }
+
+       rx_virt = hyp_phys_to_virt(rx);
+       ret = hyp_pin_shared_mem(rx_virt, rx_virt + 1);
+       if (ret) {
+               ret = FFA_RET_INVALID_PARAMETERS;
+               goto err_unpin_tx;
+       }
+
+       host_buffers.tx = tx_virt;
+       host_buffers.rx = rx_virt;
+
+out_unlock:
+       hyp_spin_unlock(&host_buffers.lock);
+out:
+       ffa_to_smccc_res(res, ret);
+       return;
+
+err_unpin_tx:
+       hyp_unpin_shared_mem(tx_virt, tx_virt + 1);
+err_unshare_rx:
+       __pkvm_host_unshare_hyp(hyp_phys_to_pfn(rx));
+err_unshare_tx:
+       __pkvm_host_unshare_hyp(hyp_phys_to_pfn(tx));
+err_unmap:
+       ffa_unmap_hyp_buffers();
+       goto out_unlock;
+}
+
+static void do_ffa_rxtx_unmap(struct arm_smccc_res *res,
+                             struct kvm_cpu_context *ctxt)
+{
+       DECLARE_REG(u32, id, ctxt, 1);
+       int ret = 0;
+
+       if (id != HOST_FFA_ID) {
+               ret = FFA_RET_INVALID_PARAMETERS;
+               goto out;
+       }
+
+       hyp_spin_lock(&host_buffers.lock);
+       if (!host_buffers.tx) {
+               ret = FFA_RET_INVALID_PARAMETERS;
+               goto out_unlock;
+       }
+
+       hyp_unpin_shared_mem(host_buffers.tx, host_buffers.tx + 1);
+       WARN_ON(__pkvm_host_unshare_hyp(hyp_virt_to_pfn(host_buffers.tx)));
+       host_buffers.tx = NULL;
+
+       hyp_unpin_shared_mem(host_buffers.rx, host_buffers.rx + 1);
+       WARN_ON(__pkvm_host_unshare_hyp(hyp_virt_to_pfn(host_buffers.rx)));
+       host_buffers.rx = NULL;
+
+       ffa_unmap_hyp_buffers();
+
+out_unlock:
+       hyp_spin_unlock(&host_buffers.lock);
+out:
+       ffa_to_smccc_res(res, ret);
+}
+
 /*
  * Is a given FFA function supported, either by forwarding on directly
  * or by handling at EL2?
@@ -132,10 +282,21 @@ bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt)
        if (!is_ffa_call(func_id))
                return false;
 
+       switch (func_id) {
+       /* Memory management */
+       case FFA_FN64_RXTX_MAP:
+               do_ffa_rxtx_map(&res, host_ctxt);
+               goto out_handled;
+       case FFA_RXTX_UNMAP:
+               do_ffa_rxtx_unmap(&res, host_ctxt);
+               goto out_handled;
+       }
+
        if (ffa_call_supported(func_id))
                return false; /* Pass through */
 
        ffa_to_smccc_error(&res, FFA_RET_NOT_SUPPORTED);
+out_handled:
        ffa_set_retval(host_ctxt, &res);
        return true;
 }
@@ -143,6 +304,7 @@ bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt)
 int hyp_ffa_init(void *pages)
 {
        struct arm_smccc_res res;
+       size_t min_rxtx_sz;
 
        if (kvm_host_psci_config.smccc_version < ARM_SMCCC_VERSION_1_2)
                return 0;
@@ -161,11 +323,37 @@ int hyp_ffa_init(void *pages)
        if (res.a2 != HOST_FFA_ID)
                return -EINVAL;
 
+       arm_smccc_1_1_smc(FFA_FEATURES, FFA_FN64_RXTX_MAP,
+                         0, 0, 0, 0, 0, 0, &res);
+       if (res.a0 != FFA_SUCCESS)
+               return -EOPNOTSUPP;
+
+       switch (res.a2) {
+       case FFA_FEAT_RXTX_MIN_SZ_4K:
+               min_rxtx_sz = SZ_4K;
+               break;
+       case FFA_FEAT_RXTX_MIN_SZ_16K:
+               min_rxtx_sz = SZ_16K;
+               break;
+       case FFA_FEAT_RXTX_MIN_SZ_64K:
+               min_rxtx_sz = SZ_64K;
+               break;
+       default:
+               return -EINVAL;
+       }
+
+       if (min_rxtx_sz > PAGE_SIZE)
+               return -EOPNOTSUPP;
+
        hyp_buffers = (struct kvm_ffa_buffers) {
                .lock   = __HYP_SPIN_LOCK_UNLOCKED,
                .tx     = pages,
                .rx     = pages + (KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE),
        };
 
+       host_buffers = (struct kvm_ffa_buffers) {
+               .lock   = __HYP_SPIN_LOCK_UNLOCKED,
+       };
+
        return 0;
 }

diff --git a/include/linux/arm_ffa.h b/include/linux/arm_ffa.h
index c87aeec..b9f8103 100644 (file)
--- a/include/linux/arm_ffa.h
+++ b/include/linux/arm_ffa.h
@@ -94,6 +94,14 @@
  */
 #define FFA_PAGE_SIZE          SZ_4K
 
+/*
+ * Minimum buffer size/alignment encodings returned by an FFA_FEATURES
+ * query for FFA_RXTX_MAP.
+ */
+#define FFA_FEAT_RXTX_MIN_SZ_4K                0
+#define FFA_FEAT_RXTX_MIN_SZ_64K       1
+#define FFA_FEAT_RXTX_MIN_SZ_16K       2
+
 /* FFA Bus/Device/Driver related */
 struct ffa_device {
        int vm_id;