[PATCH v1 08/17] xen/riscv: add IMSIC state save/restore

IMSIC state is currently needed only to track which physical CPU owns a
vCPU's IMSIC interrupt file. This is required because the physical CPU
ID is part of the physical address used to map the IMSIC file.

Add imsic_state_save() to record the current pCPU for a vCPU. When the
vCPU is migrated to a different pCPU, the mapping will need to be updated.

When imsic_state_restore() is called, VGEIN is already assigned to the
vCPU and the guest interrupt file is already mapped, and, as only h/w
interrupt files are used for now, nothing specific needs to be done.
Action is only required when the vCPU is moved to a different pCPU, which
requires recalculating VGEIN and the mapping for the new guest interrupt
file. That will be handled separately by vcpu_move_irqs(), which is
introduced in a follow-up patch; until then this case is guarded by a
BUG_ON(), which is fine.

Co-developed-by: Romain Caritey <[email protected]>
Signed-off-by: Oleksii Kurochko <[email protected]>
---
 xen/arch/riscv/imsic.c             | 23 +++++++++++++++++++++++
 xen/arch/riscv/include/asm/imsic.h |  3 +++
 2 files changed, 26 insertions(+)

diff --git a/xen/arch/riscv/imsic.c b/xen/arch/riscv/imsic.c
index 2a792e756c4e..406bc68cbcd1 100644
--- a/xen/arch/riscv/imsic.c
+++ b/xen/arch/riscv/imsic.c
@@ -20,6 +20,7 @@
 #include <xen/init.h>
 #include <xen/libfdt/libfdt.h>
 #include <xen/macros.h>
+#include <xen/rwlock.h>
 #include <xen/sched.h>
 #include <xen/smp.h>
 #include <xen/spinlock.h>
@@ -418,6 +419,28 @@ int imsic_map_guest_file(struct vcpu *v, unsigned int vsfile_id)
     return res;
 }
 
+void imsic_state_save(struct vcpu *v)
+{
+    struct vimsic_state *imsic_state = v->arch.vimsic_state;
+    unsigned long flags;
+
+    /*
+     * SW interrupt file always has ->vsfile_pcpu = NR_CPUS so nothing specific
+     * should be done in this case.
+     */
+    if ( !vcpu_guest_file_id(v) )
+        return;
+
+    write_lock_irqsave(&imsic_state->vsfile_lock, flags);
+    imsic_state->vsfile_pcpu = cpuid_to_hartid(v->processor);
+    write_unlock_irqrestore(&imsic_state->vsfile_lock, flags);
+}
+
+void imsic_state_restore(struct vcpu *v)
+{
+    /* Nothing to do */
+}
+
 int vcpu_imsic_init(struct vcpu *v)
 {
     struct vimsic_state *imsic_state;
diff --git a/xen/arch/riscv/include/asm/imsic.h b/xen/arch/riscv/include/asm/imsic.h
index 8e3797690f99..cfb968204a08 100644
--- a/xen/arch/riscv/include/asm/imsic.h
+++ b/xen/arch/riscv/include/asm/imsic.h
@@ -110,4 +110,7 @@ int vimsic_make_domu_dt_node(struct kernel_info *kinfo, unsigned int *phandle);
 
 int imsic_map_guest_file(struct vcpu *v, unsigned int vsfile_id);
 
+void imsic_state_save(struct vcpu *v);
+void imsic_state_restore(struct vcpu *v);
+
 #endif /* ASM_RISCV_IMSIC_H */
-- 
2.54.0