[Minios-devel] [UNIKRAFT PATCH 05/23] plat: Hardware context - Yield thread to a previously yielding thread

[Costin Lupu <costin.lupu@xxxxxxxxx>]

This is the switching scenario that also occurs for cooperative scheduling,
therefore the isn't anything special with it. We just use the hardware context
instead of the software context.

Signed-off-by: Costin Lupu <costin.lupu@xxxxxxxxx>
---
 plat/common/x86/hw_ctx.c       | 10 ++++++++++
 plat/common/x86/thread_start.S | 12 ++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/plat/common/x86/hw_ctx.c b/plat/common/x86/hw_ctx.c
index 778e546d..edee3aee 100644
--- a/plat/common/x86/hw_ctx.c
+++ b/plat/common/x86/hw_ctx.c
@@ -90,6 +90,8 @@ void hw_ctx_start(void *ctx)
        UK_CRASH("Thread did not start.");
 }
 
+extern void asm_hw_ctx_switch(void *prevctx, void *nextctx);
+
 static void hw_ctx_switch(void *prevctx, void *nextctx)
 {
        struct hw_ctx *prev_hw_ctx = prevctx;
@@ -101,6 +103,14 @@ static void hw_ctx_switch(void *prevctx, void *nextctx)
                /* IRQ context */
                prev_hw_ctx->interrupted = true;
                next_hw_ctx->interrupted = false;
+
+       } else {
+               /* yielding */
+               if (next_hw_ctx->interrupted) {
+
+               } else
+                       /* switching yielding to yielding */
+                       asm_hw_ctx_switch(prevctx, nextctx);
        }
 }
 
diff --git a/plat/common/x86/thread_start.S b/plat/common/x86/thread_start.S
index 105691ee..363d86c3 100644
--- a/plat/common/x86/thread_start.S
+++ b/plat/common/x86/thread_start.S
@@ -68,3 +68,15 @@ ENTRY(asm_sw_ctx_switch)
 1:
        PROTECTED_REGS_RESTORE
        ret
+
+ENTRY(asm_hw_ctx_switch)
+       PROTECTED_REGS_SAVE
+       movq %rsp, OFFSETOF_REGS_RSP(%rdi)       /* save ESP */
+       movq OFFSETOF_REGS_RSP(%rsi), %rsp       /* restore ESP */
+       movq $1f, OFFSETOF_REGS_RIP(%rdi)        /* save EIP */
+       pushq OFFSETOF_REGS_RIP(%rsi)            /* restore EIP */
+       ret
+1:
+       PROTECTED_REGS_RESTORE
+       ret
+
-- 
2.20.1


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