On 12/11/25 12:02 PM, Jan Beulich wrote:
On 11.12.2025 11:29, Oleksii Kurochko wrote:
On 12/8/25 4:05 PM, Jan Beulich wrote:
On 01.12.2025 11:24, Oleksii Kurochko wrote:
--- /dev/null
+++ b/xen/arch/riscv/vsbi/vsbi-legacy-extension.c
@@ -0,0 +1,37 @@
+
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <xen/lib.h>
+#include <xen/sched.h>
+
+#include <asm/processor.h>
+#include <asm/vsbi.h>
+
+static int vsbi_legacy_ecall_handler(struct vcpu *vcpu, unsigned long eid,
+ unsigned long fid,
+ struct cpu_user_regs *regs)
+{
+ int ret = 0;
+
+ switch ( eid )
+ {
+ case SBI_EXT_0_1_CONSOLE_PUTCHAR:
+ printk("%c", (char)regs->a0);
This is guest output, so shouldn't use plain printk().
I think that I don't know what should be used instead. Could you suggest me
something
or point to the code in other arch-s?
Or do you mean that guest_printk() should be used?
No direct replacement will do what you want, as they all prefix something to the
string passed (which isn't what you want). You may need to buffer characters and
emit them in batches (full lines unless overly long). For x86 see
hvm_print_line(),
but I think Arm also has something like this.
I don’t recall anything like that for ARM. The only thing related to character
buffering that I remember is in vpl011_write_data_xen()
(https://elixir.bootlin.com/xen/v4.21.0/source/xen/arch/arm/vpl011.c#L76), but
it
does not use the buf declared in struct domain_console. Instead, it provides a
separate structure for vpl011:
struct vpl011_xen_backend {
char in[SBSA_UART_FIFO_SIZE];
char out[SBSA_UART_OUT_BUF_SIZE];
XENCONS_RING_IDX in_cons, in_prod;
XENCONS_RING_IDX out_prod;
};
I don’t see that ARM uses struct domain_console.
By the way, I can’t find a counterpart of hvm_print_line() for reading a
character(s).
Is domain_console->buf intended to be used only for writing characters?
+ default:
+ panic("%s: Unsupported ecall: FID: #%lx, EID: #%lx\n",
+ __func__, fid, eid);
Please don't. domain_crash() may be okay to use here, but crashing the
hypervisor
because of unexpected guest input isn't okay.
|domain_crash()| is better. I also considered just
returning|SBI_ERR_NOT_SUPPORTED|,
but it wasn’t too convenient for debugging which FID/EID the guest was called,
so I started using|panic()| instead.
FTAOD - domain_crash() is acceptable here while things are still under
development.
It shouldn't stay like this in the end though: Guests should not be punished
like
this for something Xen hasn't implemented.
Agree, I will create a task in my Xen's repo to not forget to drop
panic()/domain_crash().
~ Oleksii
